Conference vmszoo::rc

    Tom,
    If you want to go cheap on a charger, there is a schmetic in the
    Febuary 87 issue of RC CAR ACTION. It can be built from spare
    parts lying around the garage or $10 bucks worth of parts from
    RAIDO SHACK. It can also be sold for $20 bucks at the track.
    
    							Rick

    I am a little puzzled as to how you can connect your charger with
    reversed polarity.  All of my units including my home brew ones
    have connectors that prevent this from happening.  I would suggest
    that everyone do this to prevent such disasters from occuring.
    If you ever reverse charge your battery pack, make sure that you
    check the batterys carefully after charging up in the proper
    polarity.  Nicads tend to short out if reverse charged.  I have
    seen packs that never recover from being reverse charged.  By the
    way, I have also seen packs that have lost a cell still flying.
    I flight pack will still function on three cells.  It is wise to
    check the battery pack voltage every so often to make sure that
    this doesn't happen.  
    	On the subject of Nicads, it is also unwise to ever completely
    discharge a battery pack by leaving the system on.  I know that
    this happens to everyone sometime by accident, but never do it on
    purpose to cycle your batteries.  The reason for this is that you
    can reverse charge some of the cells and possibly ruin them.  The
    more cells you have in series, the more likely this can happen.
    This is the reason you should not replace cells in a battery pack
    individually.  The weakest cell will get the least charge and will
    discharge fully before the others.  If the battery pack is further
    discharged, the dead cell will try to reverse charge and short.
    If possible, never take the battery voltage below 1.1 volts per
    cell.  
    	One last comment.  If you are in doubt about the quality of
    any of your flight batteries, find another use for them where their
    failure is not disaster such as photo flash or walkmans and replace
    them with new ones.  It's cheap insurance.
    

    I never said anything 'bout reverse polarity. I was told that the
    design of the charger jack, could, in some cases, cause a short
    if the jack is not inserted properly into the Tx. reverse polarity
    will not occur using the supplied manuacturer's equipment
    
    
    md

    Charlie/Marc,
    
    In my case, the charger jack/plug (3-pin Dean connectors) has a pol-
    arizing groove molded into it but it can "still" be plugged in back-
    wards.  I simply wasn't paying enough attention when I committed
    my faux-pas.  Good points about not totally discharging nicad cells.
    Their affinity for reversing polarity at low/no voltage levels is
    well known and is to be avoided like the plague!
    
    Adios,	Al

    Along with several others, I have just acquired through Jeff an L R
    Taylor Model 300 Power Pacer Nicad cycler/charger.  As a cycler, it
    seems well designed; as a charger, it is a bit primitive --- the user
    is expected to remove it when the batteries are fully charged. There
    are chargers on the market that employ more elaborate circuitry like
    peak detection to fully automate the charging process, but not this
    one.  I like the Taylor unit, so I consider it a base for future
    expansion as a home-brew project.  Marketing a full-function unit might
    be a sticky mess of patents and negotiations, but as individual users,
    I believe we can build (i.e. copy or scratch design) anything for our
    own use.  When [and if] I get to it, I'll report the results here.  In
    the meantime, I'd happily follow the work of others; I want the
    results, not the credit. 
    
    Unrelated to the charging control is the limitation in R/C chargers to
    two common voltages --- 4.8v and 9.6v in my case.  One of my early
    modifications to the Taylor unit will be the addition of 3.6v, the
    requirement of my favorite flashlight.  The chargers I have been using
    for the flashlight for years without complete satisfaction have been
    two 2 cell chargers.  I don't need to measure the remaining energy in
    the flashlight batteries at the time of discharge, so I should be able
    to add 3.6v to the Taylor unit with ease, especially if I'm modifying
    the unit anyway.  

    The Taylor Power Pacer 300 is shipped without connectors --- a
    reasonable shortcoming in a world of many parochial [non]standards.  As
    recommended, I acquired a pair of connectors for my Futaba system.
    That approach is expensive, wimpy, and limiting, especially since I
    want to use the Taylor for other applications, and I have other
    tools that need access to any of my battery systems.
    
    So I set about to insert a "standard" connector in the charging path
    and to build adapters, when necessary, for each special application.
    For example, by wiring to my expanded scale voltmeter a "standard"
    female connector like the one now on my charger, I can immediately
    check any battery system that I have adapted to a "standard" male
    connector --- it works and works well --- I have just used it on a
    little "9.6v transistor battery".  Clip leads would have worked on that
    battery, but some systems are not suitable for clip lead access.  I can
    build a "standard"-male-connector to "standard"-female-connector cable
    with a break to insert a sensitive and accurate ammeter that I happen
    to own; then I can directly measure the charge and discharge currents
    for any of my systems. 
    
    
    
    The standard I selected is the old "phono" plug/jack standard that
    looks a lot like a cheap coax connector.  It is a simple, inexpensive,
    and commonly available tip-and-ring system often used in home music
    systems, especially before stereo became commonplace.  I think it is
    called a Motorola plug/jack. It is about 5/16ths in diameter, easy to
    use, and quite sturdy.  The Radio Shack in-line units I bought were
    less than 50 cents each: 
    
    	Phono plugs (4)			Cat 274-319	$1.79 for four

    	Inline phono jacks (4)		Cat 274-337	$1.49 for four

    By contrast, the Futaba connectors seem to cost at least $4 each.
    I'm willing to pay that for an airborne application, but it is not
    cost effective on the workbench.

    
    I looked into another possible standard --- the coaxial DC power
    plugs/jacks that are on the market for Nicad applications.  Good grief!
    They are very similar, but utterly incompatible because they needlessly
    differ slightly in dimensions.  For example, I have two in my hand now
    --- one with a 5.5 mm O.D. and a 2.5 mm I.D. (#274-1573, $1.19/two)
    --- one with a 5.0 mm O.D. and a 2.1 mm I.D. (#274-1567A, $1.19/two),
    and there were five others at Radio Shack, all similar.  The first of
    these is identical to the Futaba transmitter connector and a lot less
    expensive; it also happens to be the same as the connector for my
    Makita drill.  However, in-line jacks are not readily available, so I
    went with the phono connectors, and I'll use these others as my 
    application adapters. 

    	I have a trick that some of you might find handy if you want
    to charge or discharge a pack with less cells than your charger
    or cycler is designed for.  If you put two silicon diodes in series,
    you get about the same voltage drop as one nicad cell.  You can
    make up dummy batteries to add in series with a pack this way as
    long as you don't exceed the diodes' current rating.  The other
    solution is to design a charger that doesn't care how many cells
    you hook up to it.  (A current source)
                          
    	Another interesting project is a charger that plugs into a car's
    cigarette lighter with outputs for transmitter and receiver packs.
    During the flying season I leave my plane in the car overnight since
    I try to fly at lunch time whenever I can.  I have been too busy
    (lazy) to build one, but I have a design almost done.  I want it
    to be just like the charger that comes with the radio complete with
    the leds that tell me it's doing its thing.  You can pull 50ma for
    two battery packs out of a car battery for days without discharging
    it.  I fast charger with peak detecting could be built to top off
    your flight batteries at the field as well.
    
    Charlie

    I just picked up some 7 cell battery packs and have questions about
    charging them.  I thought this would be a good place to ask.  (I could
    go back and ask the shop I bought them from but it's more fun to ask
    here.)

    The battery packs use "Sanyo SC's" and are 1200mah and 8.4v.  I'm not
    sure what the 8.4v means when you're charging but my understanding is
    that 1200mah means that at 3 amps they must be charged for 24 minutes. 
    Does that sound about right.  My charger's directions say "Charge
    1200mah batterys at 4.5 amps for 15 minutes" which it can do with a 6
    cell battery but it doesn't seem to reach 4.5 amps with a  7-cell
    battery, it only outputs 3 amps.   It also doesn't continuously output 3
    amps, it tails off during the charge, how should this drop be reflected
    in a charging time.

    The directions for the batteries say "charge at 3-4 amps until peak is
    detected or the battery becomes warm" which are useless directions
    because I don't have a peak detecting charger and the charger I use
    measures time not temp.

    For the record, the charger is a Protech 701 which seems to be a decent
    charger although it doesn't have a very comprehensive set of
    instructions.  For example, it has a boost switch that the instructions
    say to use when charging batteries with 7 or more cells.  Anybody out
    there know what this boost switch does?

    I used to use a heat seeking Astroflite charger but it claimed it only
    worked with 6 cell batteries (and I believed it, can this be true?). 
    The heat seeking part wasn't real reliable, especially with the cheap
    batteries I use, but it did have an amp gauge that I found useful.  I'd
    charge until it dropped below 3 amps and I was done (btw, the Protech
    instructions also say to stop at 3 amps).  This is real useful for
    recharging batteries that aren't fully discharged.  (Hey! I heard that
    cringe!)  This approach didn't seem to work with SCR's though because
    they seem to be willing to eat huge quantities of amps until they blow
    up.

    Is there a similar cut-off point for 7-cell batteries?  Are they full
    when they drop off to 2amps?  Hopefully the drop off point isn't
    something like 2.102202453 because I'll never catch that.

    The Protech charger does have hook-ups for a voltmeter but I don't the
    slightest idea how to use one, is that something I'd better plan to
    learn?

    Well, you have hung on this long so I'll pass on one more anecdote that
    is sort of charger related.

    My Protech charger is nice and new but originally it was supposed to be
    a B&B Juice Machine.  I picked the Juice Machine because it had
    adjustable current and a 30 minute timer and, due to some small
    character flaw, I thought I needed these features.  Tower Hobbies was
    the only place I could find that carried it so I ordered a Juice Machine
    from them.  

    It took 6 business days for it to arrive (is there a slow boat from
    Illinois?).  When it arrived I checked the packing box, it was
    undamaged.  I opened the box and took out the charger, it was in a
    sealed, undamaged box.  I opened the box and the charger was in lots of
    pieces.

    I called Tower Hobbies customer support (which is closed on weekends and
    fairly busy weekdays). They were extremely polite and very apologetic. 
    They agreed to a return for refund without an argument, issued an RA #,
    and even gave me a $2 merchandise create to recover the cost of the
    call.

    The Tower Hobbies person told me that the problem was probably do to the
    cold.  The plastic backing of the charger got cold and brittle then
    stress from the assembly screws fractured it.  I'm kinda glad I found 
    the problem this way because I occasionally run outdoors in the winter
    and it can be fairly cold up here in MA.  I'd be real annoyed if the
    charger had self destructed after I'd had it for a while and then tried
    to use it outdoors.

    I ended up buying the ProTech in a local shop because I got tired of
    waiting and, for this product, the prices were competative.

    The moral of the story is that although Tower Hobbies can be fairly
    slow, they do seem like a good reputable place to do business and I
    would definitely recommend them.

    Still haven't given up yet huh?  Well I've got another charger tidbit. 

    At the races last weekend the guy next to me had one of those new
    ProTech 707 chargers.  This baby is AC peak detecting (that's right AC)
    and is real automatic.  It can supposedly peak charge one battery while
    trickle charging another.  Owner claimed it charged 6-cells batteries in
    13 minute and seven cells in 18, and he was running SCE's.  All this and
    it put on one hell of a light show at the same time.  Local prices for
    the charger is less then $100 so run right out and buy one.

    I could probably think of more but I don't think anyone will actually
    read this far so I'll sign-off here,

    --Don Senechal

    Boy,

    It seems this question comes up an awful lot.  Basically, the rule
    is, imagine your battery as a fuel tank, its capacity is 1200
    whatevers (forget about amps).  If you place a load on it that
    draws 1200 whatevers, the battery will deliver at this rate for 1
    hour before it is empty. Now you want to fill it up.  You could
    feed it 1200 whatevers, taking 1 hour to fill the battery, you
    could give it 2400 whatevers, taking .5 hours, you could give it
    4800 whatevers, and fill it in .25 hours.

    Most chargers deliver around a 3000 MA charging current, this will
    fully charge a depleted 1200 MAH pack in 24 minutes since :
	1200 MAH/ 3000 MA = .4 Hours = 24 minutes.

    In reality, no battery is ever really "empty", so charger
    manufacturing companies "derate" this a little to keep you from
    damaging your battery (really, all they care about is that you
    don't start a fire because the battery is overcharged, since if
    you did burn your house down, they might get sued).  Anyway, a 3
    amp charge will fully charge your battery in 20 minutes, lets say.
    Now, you put a 8.4 V battery on the charger instead of a 7.2 Volt
    battery.  The charger is current limited (probably by a low value
    resistor), so the additional volatge required by the higher
    voltage battery means the current delivered by the charger will be
    lower by a corresponding percentage, remember that P=VI, so the
    charge rate decreases by (8.4-7.2)/8.4 or 14%, and the charge time
    goes up by the same amount. 

    You can Peak charge batteries yourself if you have a voltmeter
    (digital is best), simply watch the voltage across the battery
    while the charger is on.  Keep charging until you see the voltage
    peak, and then start to  drop, and then turn off the charger.
    When I peak charge with my mechanically timed charger at home, I
    typically see the voltage across a 6 cell pack climb to about 10.5
    volts before it starts to drop.  Of course, I also sometimes just
    charge the sucker until it starts to get nice and toasty warm to
    the touch, and don't bother about the peak level. 

    AC chargers are really Pulse chargers.  Rather than deliver a
    constant current charge of, say, 3 amps, they deliver a 50% or 75%
    dutycycle pulse of 4.5 or 5.25 amps. The average current going
    to the battery is the same, but supposedly the battery charges
    faster, with less electricl and mechanical stress than a constant
    current charger.

    re:  < Note 834.1 by LEDS::COHEN >
    
    Thanks, that's a lot of good information that I am sure I can put
    to good use.  The "1200 MAH/ 3000 MA = .4 Hours = 24 minutes" part
    is mention in elsewhere in the notes file but I thought I should
    check so I didn't blow up any batteries.  The guys down at the track
    recommended that I charge for 15 minutes then for 5 more then until
    the battery starts to get warm.  I was trying to get something a
    little more exact.
    
    The "(8.4-7.2)/8.4" part explains why my charger charges at a lower
    rate when using seven cells.  I thought it was because of some special
    circuitry required to handle 7 cell batteries but this sure makes more
    sense.  It explains why hooking up a 7 cell battery to my Astroflite
    charger also charges at a reduced rate even though it's rated for
    6-cells batteries.  Must be rated that way because it gets so hot it
    would melt before before it finished charging a 7 cell battery.
    
    The voltmeter sounds like a hot tip, I'll have to look into it. Can the
    voltmeter hook directly to the battery or does it need a special
    connection on the charger (the Protech has one, the Astroflite
    doesn't)?  Can I make a connector for between the charger and the
    battery with a connection for the voltmeter? 
    

    A question for anyone who has a ProTech charger:  What does the
    boost switch do?   I assume it somehow raises the output current,
    if so, does this mean I can use it charge SCR's at a higher rate?
    
    
    Thanks again,
    -- Don Senechal
    

RE: Connecting the Voltmeter

Direct to the battery is fine (no special connection is required).  A connector
between the battery and charger will also work.

Brad

    A couple of answers:
    
    When the battery starts to get warm, it's overcharging so that's
    the point to stop.  If you carefully monitor it after most of the
    charge cycle by holding on to it, you can get a nice full charge
    this way without hurting the battery.  The best charge rate for
    fast charging is about three times the rating or 3.6 to 4 amps for
    a 1200 pack.  Some chargers go to 4 times the rating but this is
    pushing it.  If you look at the data sheets, you will see that
    these batteries are not designed to charge that fast.  Also,
    trickle charge new packs before fast charging them to balance the
    cells.  (Discharge them before the fast charge of coarse)
    
    	Another point:  You can't charge a 7 cell pack off of a car
    battery at much more than 4 amps because you run out of volts.
    That's why your current tapers off when the battery reaches a
    partial charge.  The charger is not designed to do this but it has
    no choice.  Some chargers "boost" the voltage by using a converter
    to step up the voltage to more than 12.5 volts to charge more than
    7 cells.  This is why it's a good idea to use peak charging or
    temperature charging since the time is variable depending on the
    temperature of the batteries and the initial state of charge of
    the pack to be charged.  The output voltage of a car battery changes
    with temperature so the charge current will also.
    
    Charlie
    

    I've been doing homework on the topic of overcharging and trickle
    charging of NiCad batteries, and this note reflects my understandings
    on the topic.  I'm including this collection here for three reasons:
    because NiCads are important to all of us, because I learned that some
    tempting practices would cause permanent damage to my packs, and
    because writing the entry forced a little more clarity in my own
    understanding.   References are listed at the end. 
    
    It seems that the NiCads that consumers and modelers use are designed
    to be "overcharged".  Under "proper" conditions overcharging will not
    damage or shorten the life of the battery nor will it overly charge the
    battery; it will keep it at full charge, ready to use.  The negative
    experiences some people have had with overcharging are probably
    associated with a violation of these proper conditions.  What are the
    "proper conditions"?  They are a set of relations between the charge
    rate, the pack's state of charge, the ambient temperature, and the
    capacity of the battery.  If you do all of your charging at the
    standard C/10 (discussed in note 53.70) at ROOM TEMPERATURE, then you
    probably don't care about the rest of this note. 
    
    I believe all of the NiCads we use are known to battery engineers as
    "sealed, sintered plate" NiCads.  The "sealed" part of the description
    is the critical word.  These batteries really are sealed, not vented;
    the little holes we sometimes see are the emergency pressure relief
    paths, not open vents.  Inside, the holes are blocked unless the
    pressure exceeds something like 100 psi (because the proper charging
    conditions were violated).  If that hole is *ever* unsealed, chemicals
    will escape, and the cell should no longer be trusted; Eric Henderson
    correlated evidence of a white powder with distinct cell failures. 
    Venting is usually, but not always, the result of letting your
    batteries get very hot while they are being charged or used.
        
    The pressure relief mechanism is an emergency device; there are
    chemical processes to deal with routine overcharging.  When the cell is
    fully charged but still on the charger, several steady state, cyclic
    reactions are taking place involving the production and migration of
    chemicals within the cell.  This converts the incoming energy into heat
    and internal pressure, so some internal pressure is expected and
    normal.  However, if the chemical reactions and migrations are not fast
    enough, or if the heat cannot escape as fast as the incoming energy
    produces it, the pressure will build up and open the vent, and
    chemicals will escape.  Our problem is to control the combination of
    charge rate and environmental temperature, both during charging and
    during overcharging.  My immediate concern is the slow overcharge
    situation.  I'm not into fast charging --- yet. 

        
    The popular literature usually recommends a charge rate of C/10 for
    about 14 hours for a fully discharged battery.  Most of the authors
    (the GE book, for example) suggest that this rate can be continued as a
*   deliberate overcharge rate.  According to Perez (his Figure 3-9) this
*   overcharge rate is too high above a cell temperature of about 95F ---
*   easily attainable on a hot summer day or perhaps by a battery on a
*   sunny window sill.  Perez doesn't indicate the particular product line
    to which this data applies or if the limitation is generic, but this
    might account for the various opinions about C/10 overcharging. 

    The lower limit of a sensible trickle charger is related to the
    self discharge behavior of the battery.  NiCads lose from 1% to
    3% of their charge per day.  Three percent per day corresponds to
    C/800, but the compensating charge must be much higher to allow
    for inefficiencies in the process.  A trickle rate of C/100 to C/33
    is suggested in the GE book.
    
    Note that you should not use a trickle charger to do the primary
    charging of NiCads.  It doesn't do any permanent harm, but it doesn't
    fully charge them.  I believe a C/20 rate during the entire charge will
    leave the battery 25% shy of full even after a long time. I don't know
    one way or the other if a battery first charged at C/10 and then
    maintained at C/20 will actually lose any energy.  I'll soon learn.
    
*   Note also that NiCads should not be charged in a cold place either;
*   cold interferes with the chemical processes.  A plane can be stored
*   with its receiver pack in an unheated garage in the winter, but
*   the pack can be permanently (and cumulatively) damaged by charging
*   it where it is much below room temperature.
    
    A graph in Perez implies that C/20 is safe up to about 115F, so I
    decided to design a trickle charger for approximately C/20 over a broad
    range of batteries.  The design is documented in a following note. 


    References:
    
    David Linden,	Handbook of Batteries and Fuel Cells, 
    			McGraw-Hill, 1984, ISBN 0-07-037874-6, ~$89.
    			Digital library in MLO4
    
    			A good book on this topic, but disappointing
    			in that it doesn't reference the data sources.
    
    
    Richard Perez,	The Complete Battery Book,
    			Tab, 1985, ISBN 0-8306-1757-4 (ppr), ~$17 ??
			Nashua Public Library
    
    			Well worth the money if only for the lead/acid
    			information that was a surprise to me.  However,
    			much data is needlessly missing, and there are
    			no links to the literature.  The book is directed
    			at home power generation and storage.
    
    
    General Electric	Nickel-Cadmium Battery Application Engineering Handbook
    			published by GE in '71, '75
    
    			More volume of information than the other two,
    			but some important data missing and none of it 
    			very recent.  Worth buying.

    
    	So, are you saying that if I cycle my packs (15hrs) tonight (Tuesday)
    and don't fly until next Wednesday, that my packs will only deliver
    40%! 
    	I also cycle/charge them in my cellar which is about 35-40
    degrees...brrrrrrr, and leave them there until I fly.  I take it
    this isn't a good practice?
    
    Concerned!!

    My understanding of the "Cold" issue is that you need only be concerned
    with temperatures at or below freezing.  It's not that the cells
    actually freeze, since the electrolyte doesn't have all that much water
    in it, but that freezing is low enough that the chemical processes are
    affected.  The cells actually freeze at something like 10 or 20 degrees
    (I can't remember where I heard this, so...) and when they do, they are
    physically damaged, and can no longer be relied upon to work.

    Many car racers cool their packs while they are charging them, and
    before a race.  From what I've been told/read, a colder pack actually
    discharges slower.  Ideally, to get the highest rate, the pack should
    start out at about 70 degrees.

    Of course, all this is dimly recalled memory.  I can't claim it's right,
    and, given a more accurate reference than my brain, I'de be happy to
    admit I'm wrong.

re  Notes 790.6 and .7     issue of charging in the cold
    
    Ken, I think you're marginal at 35 to 40F.
    
    Randy, your understanding is very, very close to the mark.    
    
    
    It has to do with hydrogen generation and accumulation --- which can
    build up pressure and vent the cell without ever warming it.  Worse
    still, the hydrogen may possibly accumulate with each charging until it
    does finally vent.  Freezing of the electrolyte itself is evidently not
    a problem; NiCads can be stored and, at very low currents, even used at
    temperatures down to -40 --- almost everywhere in New England but the
    Northeast Kingdom, Ken.
    
    According to section 4.3 in the GE book, C/10 is safe down to about
    40F, and the safe rate drops linearly down to C/50 at a few degrees
    below zero Fahrenheit.  My garage/workshop is often down to 10F during
    the winter, hence my reluctance to do any overnight charging out there
    and an intention to build a C/20 trickle charger for airplane storage
    in the garage.  C/30 would be even better.
    

re  790.5,  experimental data by Eric
    
    Thanks for the tests!  They sure seem to confirm that:

    	trickle storage wins

    	trickle top-up doesn't
    
    Do you know the C/H rate of that trickle mode on the Digipace? 
    The ACE?   The temperature(s) of the packs during the experiment?


>>    I am very tempted to buy some more of these units and plug my cars
>>    and boats in permanently. Trouble is I would need a lot of outlets
>>    in the workshop not to mention several more chargers.
    
    Hold off for a moment.  I'm working on a multi-port trickler.  Circuit
    is trivial, but parts availability at the ubiquitous Radio Shacks may
    not be; also I don't like to write about designs not yet tested.

    I have been testing my charger design for about 3 months now under
    normal use.  I have a two rate design that charges at 50 ma or 5
    ma which is C/10 or C/100 for normal radio systems.  It uses true
    current sources so you can hook up transmitters or receivers to
    the same outputs.  It can be built with four or more channels.
    It's not as simple as possible but it has an added feature that
    it monitors the current and the LED only lights if the current is
    within 10% of the desired value.  This guarantees that the connections
    are good to the battery.  By the way, the charger that comes with
    the radio systems doesn't really do this.  THe led will light if
    you have a poor connection and if you have a shorted cell, the others
    will be over charged.
    
    CHarlie
    

    Little fat on the fire. The new Futaba radio's that do have a dual
    conversion receiver (1991) have different dual rate switches. They
    are reversed. Flip down, rather than up for dual rates on Aler and
    Elev. Also noticed that my Taylor cycler won't work. I think they
    may have put a Diode in the system for some reason?
    
    Bob

    Yes I found out the same thing with my new PCM rig from Futaba.
    
    
    							Dave
    

    The Airtronics Spectra also now has a diode in the charge jack.
    THis is a royal pain in the A** because you can't cycle the battery
    from the charge jack and you can't read the pack with an ESV.
    THis must be done as a safety move so that something stuck into
    the jack can't short out the pack.  I may disable this feature to
    enable the other two features that I use regularly.  The charger
    is unchanged from my older Airtronics rigs including connectors
    so the diode serves no useful purpose other than the possible safety
    one.
    
    Charlie
    

    re   the diodes in the packs
    
    My Makita drill also has a diode.  I just started to write that the
    diode was not needed for the charging function; I checked the charger
    and it had its own diode(s), so I shorted out the pack's diode. Then I
    used my other gear with the drill's pack.  And, as before, since
    everything has a common standard connector with adapters as needed, I
    could use the Makita charger as a high capacity charger for other
    things. 
    
    There might just possibly be a problem here, hence my phrase, "I just
    started to write".         Recently I went to use the Makita charger
    and noticed that it no longer worked; the transformer had been fried.
    Hmmmn.  I'll do some checking this weekend.
    
    Anyway, I suspect that the diode is there to protect the pack if
    the charger develops a short.  Cheap insurance for a device that
    is supposedly never to supply energy outside the case --- i.e. to
    a Taylor Cycler.
    
    This is not the case with the consumer grade GE charger I bought
    years ago for my flashlight batteries.  The HOLDER that comes with
    the plug-into-the-wall-outlet "charger", has the ONLY diodes in
    the charging circuit.  Those diodes are important.  The little cube
    that plugs into the outlet has nothing but a transformer inside it.

    
    Replace the diode with a 1 amp fuse.
    
    Bill
    

re Note 920.21       Replace the diode with a 1 amp fuse.

    Convenient, safe, economical, effective.

    Why didn't I think of that?  

    I am putting together a simple 50ma charger for a 4xAA 450mAh cell 
    receiver/servo pack.  I plan to use a 78L05 in a typical current
    regulator configuration (a 100ohm resistor between the ground
    and output pins.
    
    My question is what should the no load output voltage be?  I have
    looked at a couple crude chargers around the house. They deliver
    their rated charge current at the specified battery voltage (IE.
    One is rated at 9V 200ma, is for a set of ni-cads which add up
    to 7.2V, 1100mAh) and operate at about 160% rated voltage under 
    no load conditions (the 9V one is at 15V under no load).
    
    I do not plan to get too fancy with this (automatic peak detection,
    and so on) but maybe I should add a zener in parallel with the battery
    to force the unit into a "dumb" trickle at something like 6.2V in
    case the battery is left on charge too long.  The manufacturer
    recommended a 50ma charge "overnight".
    
    Thanks,
    Walt
    
     

    I talked with Charlie Watt about .5 this morning.
    
    Since the talk was enlightening to me I thought I would share it
    with others.  Ni-cad characteristics are kind of new to me so if
    this is obvious to the rest of the free world, I appologize.
    
    First, if using a current source charger in the c/10 range (an overnite
    or 12-16 hour charge), which I am doing the actual voltage supplying
    the current source is not important as long as it is above the battery 
    rated voltage.  The battery will act as its own zener when fully
    charged, bypassing the charge current (evidenced by the charge
    voltage from the current source remaining at the battery voltage 
    level instead of rising).  The heat from the battery is the result
    of the bypassing.  In a c/10 charge rate the heat buildup is not
    serious enough to warrant heroic measures, like peak detection
    and shutdown.
    
    All the above is true in higher charge rates, except the heat developed
    when bypassing current after the battery reaches full charge during a
    so called "fast" charge rate can cause damage. This is usually why 
    timers, peak detectors and temperature sensors are used.
    
    Anyway, it appears I can set up the 50ma current source charge from
    something convienent like a 12-15 VDC source (AC transformer or auto
    battery) and charge 1 to about 8 cells in series without changing
    anything in or on the charger.
    
    Walt

re  Note 834.6    about Charlie Watt's constant current approach
    
    Charlie gave you good advice.  It is applicable for overnight charging
    of 500 mAh packs, less so for 600 mAh, and much less so for 900 mAh.
    
    See notes 790.4-.L for some other limitations and concerns.

    RE: -.1
    
    Thanks for the reference.  I began looking at that note but didnt
    get to your entry, since it looked like it was going off in a
    different direction than I was interested in.
    
    
    Last nite I put together my "simple" charger. It is not nearly as
    elaborate as what Charlie Watt is working on, but I think it will
    do nicely for TX/RX nicads.  
    
    It is the essence of simplicity.  The voltage/current source is a
    charger from one of the toys that used nicads. In this case it is
    the one rated at 9V 200ma (which idled at 15V 0ma). The current source
    (50ma) is the textbook 3-terminal IC voltage regulator connected as
    a current source.
                                    ___________
                   + DC In -->>-+--|In      Out|---+
                                |  |   78L05   |   |
                               C1  |____Gnd____|  R1
                                |        |         |
                                |        +---------+------> + 50ma out
                   - DC In -->>-+-------------------------> -
    
    			C1 => .33�f	R1 = 100 Ohm (for 50ma)
    
    
    The above is inexpensive enough that I have made a dedicated source
    for each set of batteries (TX/RX) which has the correct connector
    for the receiver battery pack and the charge connector on the
    transmitter.
    
    By changing or switching the resistor value, the current source
    can easily and reliably changed to a trickle charge.
    
    Walt

    Walt,
    	The only problem I have with the above charger is that it can't
    charge 8 cells on a car battery.  This is because you need 5 volts
    across the 100 ohm resistor.  My design will work with 8 cells on
    just over 12 volts which allows me to charge a tx pack in the car.
    Other than that, my only other gripe is no solid indication of correct
    charge current.  I consider this important for planes.  I want to know
    for sure that the charger is putting out the desired current.  By the
    way, the ones that come with radios do not do this.  The led being on
    does not guarantee that you have rated current going to the nicads.
    
    Charlie (Very dissapointed in notes) Watt
    

    
    
    		Does anyone have any plans or know where to get plans
    	for a variable current battery charger for 7.2v-8.4v RC car
    	batteries? I'd like to see if I can do this cheaper than Tower
    	can.
    						sam

    Sam,
    	Don't cut corners on chargers.  The batteries cost a bunch and you
    will get much better performance and battery life if you use a good
    charger.  Get one that does delta peak charging and you will get fully
    charged packs every time without using a timer.  I have the Kyosho one
    and I couldn't build one as good for the 70 some dollars I paid for it.
    
    Charlie
    

More modestly interesting stuff form the UNIX network

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

From: [email protected] (Ross Oliver)
Subject: Idea for recharging batteries in the field
Date: 26 Aug 89 01:09:46 GMT
Sender: [email protected]
 
I'm currently building a Goldberg Electra (electric-assist glider),
and have been pondering how to recharge the battery packs at the
flying site.  The possibility of 120-V outlets are fairly slim.
Other alternatives are to recharge from my car battery (although
parking may be inconveniently far from the flying site), or lugging
40 pounds of lead-acid battery out to the field.  Neither of these
are very appealing.  However, a third alternative occurred to me when
I read the following message in sci.electronics.  The discussion
thread concerned various methods of recharging the batteries of
electric-powered wheelchairs:
 
** From: [email protected] (Steven K Roberts)
** Newsgroups: sci.electronics
** Subject: Re: Electric cars?  Start with wheelchairs.
** ....
** I can't help but wonder why nobody ever mentions solar power in 
** discussions like this.  The Solarex SX-LITE panels weigh about 2
** pounds and put out 18 watts, at a retail cost of $175 or so.  Admittedly
** this is not cheap, but that's 1.2 amps per panel of charge
** current (they're scaled for direct connection to 12V batteries,
** and can be series-connected for 24).  Application is trivial...
** sunlight in, two wires out.  Add a schottky to prevent dark discharge
** and you're done, unless the panels are substantially more robust
** than the batteries, in which case a controller is required.  
**   Solarex is at 800-521-SOLA and a Bay Area distributor is Energy 
** Depot at 415-499-1333 in San Rafael.
**    Cheers...
**   Steven K. Roberts
**   Nomadic Research Labs
 
 
It seems to me that these solar panels could be connected directly
to battery chargers intended for use from car batteries.  Thus, you
have a virtually endless supply of 12-volt power as long as the
sun is out. $175 is a little steep for an individual flyer, but
a club with a lot of electrics might be able buy one, or even
several.  Has anyone out there tried something like this before?
Another idea: if enough solar cells to produce 18 watts weighs
only two pounds, shouldn't it be possible to build a solar-powered
R/C electric plane?
 
Ross Oliver
[email protected]

After looking at the June 89 DECRCM video last night I have some questions for
Charlie (Watt?) about his gang charger.

Not being a EE, how hard is it to put a constant current charger together and
could a similar circuit be used with a pot. for a glow plug driver (or with
a trim pot. for an in flight glow driver)?

Having heard the car buffs talk about storing packs fully discharged with a 
resistor across them, I was wondering:

1) any problems with long term trickle charging?
2) anyone try "quick" charging Tx/Rx battery packs (damn, I forgot to charge
last night so of course the weather is perfect today)

    RE :-1
    
    It is possible to do a constant current glow driver, but I would go
    with constant voltage in that application.  The purpose of using a
    constant current source in the charger design is to allow it to charge
    TX ane RX packs with no difference in current.  My charger will charge
    from 1 to 8 cell packs at the same charge current.  You really don't
    need this for a glow driver.  I do use my charger to charge my glow
    driver.
    	You can fast charge TX and RX packs, but you have to do so VERY
    carefully!  Fast charging based on time can ONLY be done if you start
    with fully discharged packs.  Usually this is not the case with TX and
    RX packs.  The only safe way to fast charge partially discharged packs
    is to do using 'peak detecting' techniques.  Only special chargers are
    capable of doing this.  500 Mah packs can be quick charged at 1.5 amps
    in about 20 minutes if you know what you are doing.  Would I do this???
    Maybe in a pinch, but not as a rule.
    
    Charlie
    

re Note 834.10    Battery charging questions    by Jim Reith 
    
>>  how hard is it to put a constant current charger together 
    
    Trivial --- one chip plus one resistor for a BARE-BONES charger.
    
    I carry one to the field with me to enable fast charging of my packs
    and my ni-starter.  However, for the reasons given by Charlie Watt in
    834.11, I never try to do more than a partial charge at the field; I
    don't want to cook my packs.  If my ESV shows a pack to be iffy, I'll
    give the pack 1250 mA for about ten or fifteen minutes, check it again
    with the ESV, and fly.  This is not nearly a full charge, but it gets
    me back in the air.  I use the exact same device in the shop on my
    small 1/4 in drill --- if the drill dies during a job, I'll revive it
    with a partial charge, use it, and put it on the standard charger
    before going to bed.  This seems to work quite well, but this is an
    exceptional procedure even for me; most of my charging is the routine,
    over-night (16 hour) charging.

    This is a BARE-BONES, constant current charger.  It has one chip plus
    one resistor --- no frills and almost no safeguards.
                                                                   
       cigarette                                                   
       lighter           +-------------+       R (see below)       
       jack              |             |                                     
    or          V+  -----+  317T chip  +------/\/\/\/\/\---+---->  pack +
       power         "in"|             |"out"              |       
       supply            +------+------+                   |
                                |"adjust"                  |       
                                +--------------------------+       
    
                V-  -------------------------------------------->  pack -
      

    The value of the resistor determines the charge current 
    (up to the 1.5 Amp limit of the 317T).
    
    	R = 1.25 / (current in Amps)       
    
    	Wattage > 1.25 * (current in Amps)       

    	For example, a 1250 mA fast charger would use a 1 Ohm resistor
    	of at least 2 Watts such as the Radio Shack 271-131.
    
    The supply must be at least 3.3 volts higher than the pack voltage BUT
    for fast charging at about 1.25 Amps NOT MORE than 13 volts higher.  So
    fast charging a ni-starter from a car battery is touch and go (the 317T
    gets very, very hot); the engine should not be running at the time.  To
    field charge a TX pack, the car engine must be running and self charging.
    The airborne pack is easy. 
    
    The 317T is carried by Radio Shack as part 276-1778.  It should be
    mounted on a heat sink such as R.S. 276-1363 with heat sink grease such
    as R.S. 276-1372.  I added a couple of connectors and mounted the
    assembly in a steel box that had been a container for a kitchen spice. 

I finally received the November R/C REPORT, which contained the second
part of their charger testing.  For $10 a year its a real bargain, if 
only for its product reviews, which pull no punches.  
    
And the winners are...

For 4 - 7 cells:  The Astro-Flight Model 110 or TRC IMPULSE IV.

For 7 - 14 cells:  The Astro-Flight Model 112.

For 14 - 28 cells: The Astro-Flight Model 112.


Both Astro-Flight chargers have diode and fuse protected inputs, short 
circuit protected outputs, and accept variable input voltages from 11-15 
vdc, with little effect on output.

A disadvantage to the peak detecting model 110, is the fixed 4.5 amp 
charge rate, which they felt was too high for 500mah packs.  It is also 
sensitive to sunlight heating the faceplate, which is also the transistor
heatsink.

On the model 112, the 1-5 amp charging rate and cell capacity (switch 
selectable 1-14, 14-28) made it the most versatile of those tested.  The 
only gripe was the 15 min. timer which must be cycled more than once for 
the large packs.  A 1200 mah 28 cell pack required 28 minutes.  Astro 
reccomends charging from a car battery with the engine running to reduce
the charge time.

The TRC IMPULSE IV, is a pulsed output peak detector, with separate output 
jacks for 3-10 cells, and 10-18 cells.  They felt that the jacks were 
less convenient and more error prone than a switch, and the charge would
shut down at 90% capacity.  Additional cycles would approach 100%.  This 
charger was also sensitive and sometimes refused to start.

Other chargers tested:

	Tekin BC100		Second choice for 4-7 cells
	Robbe Automax 21	Second choice for 7-14 cells
	Kyosho Multicharge II
	Pro-Tech Autopeak 707
	TRC Impulse II
	
  I've got an Astro-Flight Model 112 in my letter to Santa.  
		($69.99 from  OMNI-MODELS)

                <<< WEWAND::$69$DUA0:[NOTES$LIBRARY]RC.NOTE;1 >>>
                  -< Welcome To The Radio Control Conference >-
================================================================================
Note 1159.0                   charging 12v wet cell                   No replies
WOODRO::EDDINGS                                       7 lines  21-DEC-1989 09:28
--------------------------------------------------------------------------------

    Does anyone have an easy way of trickle charging a rc wet cell
    12v with a 10 amp charger?
    
    send mail
    
    john
    

As a related question:  I've just received my birthday present
from Sheldon's: a Sonictronics power panel, Royal starter, and
12V wet cell.  Soon it will be field box design time.

In that spirit, I ask:

a) How much space/ventilation should I leave around the wet cell
for safe operation?

b) Is it more dangerous during charge or during
discharge?

c) Is it safe to enclose the battery tightly and open
the top for ventilation during charge?  I ask this last one
because I'm concerned about any dangerous gasses sinking to the
bottom of the compartment and lurking there.

    a. I would leave only enough to allow easy access.
    b. Charge cycle. 
    c. Hydrogen the gas produced would rise and disipate. Removing the caps
    would allow the gas to escape but there(motorcycle battery?) should be
    a built in vent.
    
    -j

    I have a question concerning the L.R. Taylor charger/cycler.  For
    some unknown reason, I cant discharge my transmitters.  As soon
    as I connect the jack the charge light comes on.  I press the test
    button and the lights dull.  When I release the test button the
    charge light (green) comes back on.  
    
    I've tried reversing the wires just in case I connected them wrong,
    but that doesn't work.  So......what could be causing this?
    
    (by the way, it worked fine when I first got it and the flight pack
    charges and discharges just fine)
    
    
    Ken

    Re: .32, Ken,
    
    Dan's right.  Many newer Tx's have a diode in-line with the charge
    circuit which prevents you from discharging/cycling through the
    charging-jack.  My new Futaba 7UAP 1024 Tx is that way; I called Futaba
    about it and they said the purpose was to prevent those of us with
    just enough knowledge to be dangerous from frying the battery and 
    the charge circuit.  They told me to simply wire across the diode if I
    wanted to but that's void warranty so I've left it alone as I can
    readily remove the pack anytime I wish to cycle it.  Perhaps, after the
    warranty has lapsed, I'll go ahead and short past the diode for the
    convenience of cycling through the charge jack but I won't make any
    such recommendation due to the obvious paroblems one _could_ run
    into...I'll just leave it a judgement call on the part of the
    individual.
    
    Now, if the cycler _did_ actually work on the SAME Tx previously, you
    might have a problem with the cycler.  To verify, connect a separate pack
    to the charger or use jumpers/test-leads to connect directly to the Tx
    battery, bypassing the charge circuit entirely (you _may_ have to break
    one side of the battery wiring to do this), then try the cycler...it
    should work now.  If not, you may have a faulty cycler but I doubt it
    as yer' description describes EXACTLY how my L.R. Taylor behaves if I
    try to cycle through the charging jack.  Some JR radios have this diode
    and, per Dan, apparently so do some Airtronics sets.      

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    You might have a bad pack!    
    
    Finding it is a Taylor feature, not a bug.
    
    8 x 1.1 = 8.8 volts = stop-discharge-and-switch-to-charge voltage
    
    7 x 1.2 = 8.4 volts < stop-discharge-and-switch-to-charge voltage
    
    So, if one cell goes dead, the Taylor will refuse to discharge unless
    the average voltage of the other cells is above 1.257, i.e. very
    fully charged; in which case it will almost immediately switch to
    charge, and the low mAh reading tells you the story.
    
    And, as the others have said, you could have another problem.

Don't overlook the obvious.  That is also what the L.R. Taylor
unit is suppose to do if you have a bad cell.  Charge that sucker
up and put a load on it and measure the voltage.  It should read 9.6
Volts even after the load has been on it for an hour.  Looking for
a load - just leave your transmitter on.  I'll bet a Coke you have a 
bad cell.  If you can get probes in the pack measure every cell.  More
than likely they will all be the same except one cell.  Throw that one
away and use the rest for on-board ignitions (or other toys) and by a 
new pack.

Mr. Taylor's Christmas present to you was saving your airplane.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Re: .35, .36,
    
    Al (Ryder) and Kay are correct...it's certainly possible the cycler did
    its job and found a bad pack.  However, I doubt it in this case based
    on yer' description that the green light dims while the test switch is
    held but returns to full brilliance when the switch is released.  This
    is the behavior I witness when trying to cycle through the charging
    jack of a diode equipped Tx.
    
    The behavior is slightly different when a cell has gone bad: the red
    light will come on as long as the test switch is held but the circuit
    won't lock-in and the green light comes back on when the switch is
    released.  This behavior immediately indicates a bad cell.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    Even with two cells out, the red light still comes on while the
    switch is held.
    
    The symptom of an open circuit is a   _dim_   green light while
    the switch is held.  That could be a wiring continuity problem or
    a diode.

    Thanks for the input guys, but I am still using the same transmitters
    I've always used.  I have two Futaba 6NLK AM and also tried it on
    a Futaba 7FGK.  All three have the same effect!
    
    I'll try to bypass some possibles by removing the xmitter jack from
    the Taylor leads and attach the wires directly to the battery jacks.
    If this doesn't solve anything, I don't know  what will.
    
    I'll keep y'all posted as to the findings.
    
    Have a Merry Christmas and we'll talk to ya next week.
    
    
    Ken

    Ken,
    
    It now sounds like a cycler problem; among others, I also have a Futaba
    7FGK which I routinely cycle on the L.R. Taylor with no problems
    whatever.  Unless this was something added to the Tx after I bought
    mine (about 5-yr.s ago), yer's should behave the same as mine...and you
    _did_ say it "used" to cycle OK.  Check the pack carefully as described
    in one of the current replies...also the continuity from charging jack-
    to-pack.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

re:  .29

	You might want to try using a car's light bulb (in series) with the 
battery to be trickled.   Brake lite bulb for a moderate amt. of current, a 
dash lite for a smaller amount...You should use an ammeter, and play around 
with it to get desired results.   

Stick

I've got a "vintage" (that reads old ;^) bunch of Astro gear that I've been
playing around with lately and I'd like some feedback/info.

System one is an Astro 25 system from 15-20 years ago (yes Dan I know I should
now buy a Cobalt) which was stored in a fully discharged state and the batteries 
are still usable. My question is where can I get a fast charger that will handle
a 16 cell load? I looked through the Tower phone flyer and didn't see any that 
would deal with mode than 8 cells. I've charger them separately with a DVOM to
check progress (hooked direct to my car battery) but I'd like to be able to 
field charge them without rewiring. Are there chargers out there that will do
this from a 12 volt car battery (with an oscillator and transformer)?

Likewise I have a couple of old (same vintage) 05 systems. I've been flying 
these with a third servo and an on/off switch. Are there any Futaba compatible
speed controls (without spending a fortune) that will replace this? Did those
of you that were talking about a scratch built speed control ever finish your
design? I can scratch build from parts a lot easier that justifying a Tower
order (to my wife/CFO) big enough to offset the postage penalty.

BTW: none of this stuff had connectors supplied so I've used Molex in the past.
I'd love to find out about a central Mass sermos source (Active? You-Do-It?)
and where do you find this ultra low resistance wire (since I currently use
generic Radio Trash)

I'm finding it hard to get weeknight flying in after commuting home but have
a big enough yard to have some electric fun at dusk when the wind disappears.

Yes, Dan I will look harder at an ElectroStreak/Cobalt combo to get serious ;^)

Jim,

This will be short since I'm typing from home...

Astro makes a very nice DC/DC charger that will charge up to 28 cells
from your car battery.  Astro model 112.  List price $119.95 but I've
seen it in Omni Models ads for around $70.

For an inexpensive home built speed control, contact Jomar (see ads in
most R/C mags).  He only advertises fully completed units (at fairly
reasonable prices) but will also sell you the blank circuit board for
$5.  The model that'd be best for you is the SC-4 (I think).  Just make
sure you get VERY low resistance MOSFETs for the circuit.  Buy the
lowest resistance (highest cost) MOSFETs you can find.  Jomar will sell
you these too if you want.  

He also sells VERY good wire and SERMOS connectors.  What wire and
connectors you use DOES make a difference.  It's worth the investment.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

    What about the charger that was shown in the June DECRCM meeting?
    Is the schematic available?  It sounded like an excellent charger.
    
    John
    

My son's cheap Kyosho charger blew its soldered in fuse. A piece of 16 gauge 
wire would be a nice replacement but I've decided to install an externally
accessable fuse holder. I'm now faced with figuring out what to stuff the holder 
with.

Could someone suggest a properly sized fuse for charging 7.2 volt packs? I 
assume that it should be a slo-blow type. Why do they solder in an unlabelled
fuse?

BTW: While I'm in here I'm going to mount a pair of jacks for my DVOM probes to 
plug into. I hate stuffing them into the back of the charging connectors and I 
think this is how my son shorted the outputs together. I better watch out or 
I'll have a REAL charger built into this case ;^)

    re .47:
    
    We have two chargers:  The MRC timed charger uses a 3/4 amp fuse,
    and the Pro Tech peak charger uses a 2 amp fuse.  Both are fast
    blow types.  If I had to figure out a fuse value myself, it would
    go like this:  The charger puts out a little over 5 amps max into
    a 7.2 volt pack.  It does this when the pack is still charging below
    9 volts (a 6 cell pack will peak at about 10.5 volts under fast
    charge).  So I would allow for say 6 amps at 9 volts, or 54 watts.
    If there were no loses in the charger, we'd draw 54 watts from the
    AC line, which is about 1/2 amp at 120 volts.  I don't remember
    what typical transformer efficiencies are, but allowing 1/4 amp
    for transformer and other losses should be more than enough.  That
    brings us to 3/4 amp.  Then there's the rule of thumb that says
    to double your required current and use that fuse value.  That would
    mean a 1.5 amp fuse, which is a common value.  In practice I might
    go with a 1 amp and see how it lasts (while bringing spares with
    me).  
    
    I should mention that the 3/4 amp fuse in our MRC charger blew once.
    I replaced it with the same value and it has been fine.
    
    All of the foregoing assumes you want to fuse the AC and not the
    DC charger output.
    
    Tony

Actually, it's the fast DC-DC charger that he has that hooks into the automobile
battery that quick charges the RC packs. I did the surgery this weekend and used
an 8 amp fuse. After taking the old soldered in one out, I managed to clear away 
the solder enough to verify that it was a 7 amp one. I connected the quick 
disconnects for my meter leads at the same time and he used the charger this 
weekend.

One not so nice thing happened...

His car went into a not nice failure mode that must have caused a short across 
the pack and it exploded in his lap while we were waiting for the HAAF guys at
CMRCM yesterday. One of the end cells detonated with one hell of a bang and the 
end cap hit him in the stomach and gave him a bruise. Fortunately the pack was 
in the car at the time and there wasn't any other damage. He's fine but I'll 
have to meter out the car before he tries it again.

>>  the fast DC-DC charger .............and it exploded in his lap 

    Are these two related?  

    Was the pack being charged at the time of the accident?  Or was the car
    being turned on while in his lap?  Or was the car by intention supposed
    to be passive at the time?  
    
    Were all the cells hot or just the one that exploded?

The charger wasn't involved but that was why I was in that reply. I had 
replaced the soldered in fuse in the charger and added external jacks for my 
DVOM probes so we could regularly peak charge. This may not be the perfect note 
for exploding pack stories...

I don't know if the pack was uniformly hot or not. We had peak charged the pack
at the house while I was packing my stuff into the car and had just gotten to 
CMRCM. (a 45 minute ride with the pack separate from the car) I haven't gotten 
my key yet (applied last week) so I was waiting for someone to arrive and open 
the gate. My son decided that he'd set up his car while we were waiting and 
inserted the battery into the car and hooked up the leads. He got no throttle 
response and was reaching for the body retainer clips when it went off. I'd say 
it was in the car for about 15 seconds and about 5 seconds after the first 
throttle servo movement. He has the standard mechanical throttle. I haven't had 
time yet to check either the other cells in the pack or meter out the car 
circuit. I've given him strict instructions not to use the car with any of his 
other packs before I give it a clean bill of health. I want to find the problem 
or verify that everything is 100% ok. I also want to be present to control the 
next initial testing. He wasn't hurt (surprised and a black and blue spot but it 
could have been much worse) which was my initial concern. We did a chinese fire 
drill and got the h*ll out of the car when it happened. I'll put in an update
after I check out the car this weekend (I want plenty of undisturbed time to 
work it through)

    Is the car Fused?  Is it fused on the Motor Side of the speed control,
    or the Battery Side of the speed control?

    I've abused a lot of packs during charge.  My Kyosho Peak Charger sh*t
    the bed and stopped turning off.  I had a pack on charge for about 1/2
    hour before I noticed.  It was hot enough the the shrink wrap was
    softened and loose, and I couldn't hold the pack for more then a few
    seconds without getting burned.  The sucker still worked when it cooled
    off, though, and it has yet to explode.  Vented NiCads (which is what we
    use in cars and planes) are specifically designed to vent under
    pressure, it's the whole point of the damn things.  Over charging
    doesn't do anything more than cause some loss of electrolyte.  You
    should never get one to blow up.  Most likely that the cell in the pack
    was defective in some way.

    Did you make the pack yourself? (Never solder over the vent hole).

The detonation didn't have anything to do with the charging. The pack had 45 
minutes to cool off as we drove to the cmrcm field. I think the significant
thing is that the pack got put into the car, connected, radio on, throttle,
detonation. all in the space of 20 seconds. This is a second hand car that I 
picked up last fall and the two packs came with it. The packs appear to be 
commercially made. One of the two packs had a dead cell and we had put that 
one aside. We can't find the second pack so I don't know which one was being 
used. As far as I can tell, there isn't a fuse in the car. The speed control
is a heatsinked resistor with a rotary switch with 3-4 contact points. This
weekend I'll be looking at the car more and taking my DVOM to it. As promised,
I'll report back my findings.

One other thing is that we DID get throttle servo movement but there is a rx 
battery pack in the system because of the loss of control with the BEC and he 
isn't racing, just running around the yard. This means that it it unknown 
whether the battery was properly "in circuit" but the throttle did move so the 
speed control might be where the short exists. The vents might have been clogged 
but there is no way to check currently.

    Jim,
    	You should definately put a fuse in the battery lead right near the
    connector.  I nicad can self destruct very fast when shorted.  Unless
    you are racing very seriously and can't afford the voltage drop across
    the fuse and its connectors, you should always run a fuse.  If the
    motor gets stalled in a crash, you can fry the pack and the motor and
    even have the thing burn to the ground without fuse protection.  I use
    an automotive fuse as the on/off switch in my Electrostreak.
    
    Charlie
    

I will fuse it when I replace the connectors this week. I checked it out on 
saturday and found the cause of the explosion. The engine had shorted internally
and when the throttle was applied, the pack went. There is no fuse so the pack 
opened. The good news is that the pack that blew was the one with the known bad
cell (found by voltage when peak charging earlier this spring). I replaced the
motor with the stock motor and charged the good pack and my son drove around all
day sunday while I flew. I'll fuse the motor before he uses it next.

BTW: One of the reasons I did so many "runway" landings was that the first 
couple of landings he was "involved" with his car and it got to be a running 
joke that he hadn't seen it so it hadn't happened so I nailed him down next to 
me for the last few.

I've seen a couple of entries about folks designing their own chargers.
Has anyone come up with a peak detecting circuit that work well?  It 
seems as though the basic circuit is not too difficult, but the fine
tuning may require a bit of trial and error.

Thanks,
Steve

.65> I've seen a couple of entries about folks designing their own chargers.
.65> Has anyone come up with a peak detecting circuit that work well?

The current issue of QST (the amateur radio magazine) has an article on this
very subject, construction of a microprocessor-controlled peak-detecting
charger.  If anyone's interested, send me mail and I'll return photocopies.

(I've been perusing this topic in the hope that the RC world would have
invented a smart applicance which would do it all:  cycling, peak-detection
charging, and trickle charging, for variable numbers of cells and mAh.)

Re: .66

> (I've been perusing this topic in the hope that the RC world would have
> invented a smart applicance which would do it all:  cycling, peak-detection
> charging, and trickle charging, for variable numbers of cells and mAh.)

    Victor Engineering's HI-IQ does all of the above (and more) for $350
    retail.  They advertise in all of the R/C Car magazines.

    Brad

>               <<< Note 790.67 by SSDEVO::MORGAN "Brad Morgan" >>>
>                   -< Victor Engineering         has it now >-
>
>Re: .66
>
>> (I've been perusing this topic in the hope that the RC world would have
>> invented a smart applicance which would do it all:  cycling, peak-detection
>> charging, and trickle charging, for variable numbers of cells and mAh.)
>
>    Victor Engineering's HI-IQ does all of the above (and more) for $350
>    retail.  They advertise in all of the R/C Car magazines.

Brad - I just checked 4 Airplane magazines and couldn't find an add.
Sooooo

Tell me can the HI-IQ handle large batteries like 24 cells - commonly 
found on aircraft?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Kay,

    I just saw the ad. in the newest (Oct. 1990??) RCM.  Sorry, but
    I don't remember the page number and I don't have it here at work.

                                - Dan

RE: .68:

Kay,

I don't know much about electric planes, I'm an R/C car person, but I thought
they used 6-7 sub-C cells.

Are you running 24 cells in series?

The Victor Engineering HI-IQ will handle 1-8 (the software revision I got with
my printer/PC interface allows 1-10) cells (in series).  It asks for cell type
(C/D, AA or other).  Charge rates are programable from 0-15A in .1 steps or 
60-700 ma in .01 steps.  Discharge rates are programable from 0-20A (25A for 
HI-IQsr) in .1 steps with a programmable shut-off voltage.

Both the charge and discharge are linear.  The charge can be shut-off
(with or without a subsequent trickle) by peak-detect, time-limit, or (with
optional software/hardware) temperature.  

There is an auto-cycling mode allowing up to 99 cycles of charge/discharge with
adjustable cooloff times (or optionally temperature).

Brad

Are you running 24 cells in series?

Not yet - maybe some day.  Lots of 40-60 size planes do.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Kay, if watching a meter is not your cup of tea, you might want to look
    into the Astro 112 paired up with a microprocessor controlled peak 
    detector that was featured in RCM a few months back.  I don't remember
    the issue, but I could look it up if you can't find it.  
    
    The peak detector can be ordered assembled for about $110.00, and the
    Astro 112 costs only about $69.00.  For a total of $179.00, it will
    fast charge up to 28 cells with a peak/temp detecting cutoff.  I can't
    swear to it, but I would expect that it retains the 112's trickle
    charge capability.  I saw one in use at the last fun fly I attended,
    and the owner seemed quite pleased with it.

    Bonjour everybody !
    I'm looking to buy a very good (current, voltage, peak detect) and 
    versatile (accepts differents size and numbers of cells, from 1.2 to 
    12.0V ) Ni-Cad charger ( $ is not important due to a long term investment).
    Any lead would be appreciated.
    
    Thank
    /Pyerre
    
    PS: The Radio-Shack Fast charger (23-232) is it good ?

    How bad/good are these $30 peak detecting chargers with no current
    control or meters such as the astrocraft sold by omni models?
    
    What is the best "buy" (not best) charger for under $100.00
    
    I have 7 cell 900mah pack for an electric sailplane.

    I was going to get the $30 "cheap peak" but now after reading this note
    it sounds like I should invest more now than later. Now I'm leaning
    towards the astroflight 112. But I would like one that also has
    an AC input and peak detecting which I the Astroflight
    112 does not offer (I think). Also I do have a nice Fluke DVM.
    

    With all the different strategies for caring for batteries, I'm
    wondering what is the best way to achieve long-term, reliable operation
    from both the Tx and Rx packs.  One thing I've learned from this
    discussion is that properly cycled batteries are going to give better
    performance and longer life.  But what does "properly cycled" mean.
    
    Let's say I'm in the middle of the peak flying season putting in 1-2
    hour flight times 3-4 times per week and recharging the batteries after
    each session using the stock charger that came with the set.  Do I have
    to do any recycling in this steady state situation?
    
    Another scenario:  During the non-peak season, I might fly only 2-3
    times in a month, and only get in 15-60 minutes of flying each time.
    Again, I will charge up the batteries for 12-14 hours using the stock
    charger on the night before each session.  Do I have to think about
    cycling in this situation?
    
    Does the cycler help most when there is only a partial discharge,
    preventing the memory problem from occuring, or does it help to always
    cycle them?  I keep hearing that batteries only have a finite number of
    cycles before they reach the end of their useful life, so it would
    appear that doing a lot of additional cycling with a cycler will
    shorten battery life.  Is this true?  If so I would think that the most
    sensible way to approach this is to use the cycler sparingly, but
    consistent with the type of useage the batteries have been
    experiencing.  Thus, in the two scenarios above, use the cycler during
    the "off" season to insure the batteries can hold a full charge. 
    During the "on" season they are getting a full cycle on a regular basis
    so the cycler seems redundant.
    
    I'd like a sanity check on all this from those who have had experience
    with cyclers.
    
    Thanks and regards,
    Joe 

    The care and feeding of ni-cad batteries is often elevated to the
    status of a religion in the R/C world, but it sounds to me as if
    you're on the right track, Joe.
    I use an Ace Digi-Pace cycler mainly to keep track of the condition
    of my batteries. If the discharge time on a given pack changes
    significantly, then out it goes. I also use an ESV for the same
    purpose.
    Worrying about memory developing in a pack, in any resonably normal
    R/C application is not worth it. Cycling a pack for that reason
    alone is a waste of time and as you say, simply puts more wear on
    the battery.
    I'm concerned about 3 things:
    
    Discharge time from a full charge.
    
    Condition of the wiring, connectors, and solder joints
    
    Not storing the pack for long periods in a discharged condition 
            
    I've never had an in-use battery failure, but I've got several
    incipient problems using the above.
    
    Terry
    

On the comment about Nicad Religion; Amen to that bro!  I've been
bitten by that one so bad that I've resolved to never say or
write anything on the subject again.  However, due to some recent
experience I'll break the rule just a little.

I use a home-made cycler that charges constant current at 50 mA
for 15 hours, and discharges with the standard 250 mA rate for
my 500 mA tx and rx packs.  I also have a 20 mA "topping off"
charge rate for 15 hours.   The cycle load of 250 mA can also be
applied as a load for the length of time I hold a pushbutton in;
this is the way I assess if the batteries are ready for flight
after I charge them, or indeed, if they need charging at all
(sometimes they don't)

Before going further, I should add that recently there have been
several articles in the model press that have readdressed the
subject of nicad memory.  It seems that nicad memory is real,
just misnamed.  It happens not when a battery is partially run
down to the same point and recharged each time (this is the
popular story), but rather it happens when a battery is heavily
overcharged.  Its just as real as ever, though the new batteries
(manuf in last 5 years or so) are somewhat more resistant to it
than previous. Because the effect looks like the battery has
remembered its previous charge level, it has been mis-termed and
misunderstood.  The cure is the same, a deep discharge to 1.1
volts/cell.  I'll refer to this effect as memory in this
discussion.

During the active season, I find that I don't need to cycle
because I run the batteries down into the flat part of the curve
each time.  Doing this, I can use the topping off charge without
danger of overcharging the batteries.  I do do a full cycle a
couple of times a season, not to erase memory, but rather to
assess the condition of the cells.

I should also interject one of my religion points:  the preflight
range check is NOT to test the radio, but to test the batteries.
People shuck off the range test saying that once they've
installed the radio and done a first range test there's no need
to do it again; the radio installation hasn't changed.  No, but
its a good live test of the system, mainly batteries.

I collapse the antenna, walk off about 50 feet, check controls,
then shut the tx off for a couple of seconds.  Turn on again, and
wiggle the controls once more.  I do this second test to verify
that the output is not marginal, and that the system can
re-acquire the signal if lost for a second or so.  I know that
those of other religion will tell me this is nonsense.  I *know*
its nonsense, but I do it because God told me to do it, and I
will continue doing it, so screw off Jack.

Mostly though, it reassures me that the battery works, in real
time, despite the indications I've had on the load test I do at
home, and despite what the Tx power meter says.

Now to the new stuff.  I once was foolish enough to do a
presentation on nicad care and feeding.  One question that was
asked was if keeping the batteries in the garage during the
winter was harmful.  I didn't know the answer because I keep my
radio downstairs in the basement and it never occurred to me to
put it outside.

Well, if it gets cold, like freezing you won't get a full charge,
also, if they're stored out there during a cold night, they will
lose some charge.  I learned this one after I kept up my
summertime practice of putting the gear in the car overnight
before leaving for the field in the morning.  Started getting
some unexplained shorter times out of the Tx and it took a few
times to figure that one out.

Also, charge only on the night before going to the field.  A
battery will lose a significant portion of its charge just
sitting for a couple of days.  This has been particularly
critical for the transmitter, with its higher steady state load,
than for the receiver.

One last one.  We have a flier at our field who is famous for his
big airplanes, and for his ability to crash -- even more than me!
Coincidentially, he's the same one who keeps his batteries in the
cold garage.  Well, after a recent crash he mentioned that his
batteries must be good because he had just tested them with an
expanded scale voltmeter (ESV).  Then in the next breath, he
added that they must also be ok because they are 1500 mA batteries.

WRONG!!!! The standard ESV puts a 250 mA load on the batteries.
This it the correct C/2 load for 500 mA batteries, and does
produce truth on the pack's condition.  But for a 1500 mA pack,
you must load it with 750 mA, the C/2 value.  To use the standard
ESV on it, you might as well test an elephant for life signs by
sticking a pin in its butt.  It was rewarding to see his face
light up on understanding, and I notice he hasn't crashed due to
this reason, lately.

OK back to my corner.  I hereby refuse any baiting on this
subject, and will not enter any more notes here for any reason,
heretofore.

    Hello...
    
    I have a charger that just connects to my car's (or whatever) 12 volt
    battery.  Can I build a black-box that has a step-down transformer and
    bridge rectifier, maybe some caps, and feed this to my charger so I can
    run it off of AC?  If so, what kind of amperage would it draw?  Close
    to the amount that I set on the meter (4.5 amps)?
    
    I'm not "heavy" into this stuff, my son and I just tinker with a Hornet
    I bought a few years ago.  I don't want to buy a AC/DC charger as I
    probably have the parts for the black-box.
    
    Thanks!
    
    John

        I use an old slot car (anyone remember them) transformer for this
        purpose. I don't know what HO trains run on; I had O gauge that
        used 0-16vac so that doesn't help. Lots of other toys probably run
        on 12vdc, and you could borrow one of their transformers.
        
        Building such a box should be pretty easy. As you say it wouldn't
        need anything more than a transformer, bridge, and caps. The
        amperage wouldn't be anywhere near an amp. Remember that your
        meter is reading amps at 12vdc, while the transformer is drawing
        from 120vac. The transformer increases the current as it drops the
        voltage.
        
        Another option would be to use a field box starter battery to run
        the charger indoors. A friend of mine who competed in both
        Yugoslavia and Moscow did just that, so he wasn't dependent on
        local power for any of his gear. Turned out to be very wise, as
        other contestants had problems.

    OK, let's talk trickle chargers again..  Early in this note string, Al
    Ryder makes a case that the standard overnight charge at room
    temperature can be left on continuely without damage to the battery.
    
    I don't know enough to dispute it, but it was also stated that it is 
    important to keep all of the other conditions right as well..
    
    The next alternative is trickle charging...  ACE sells an in-line
    (between the charger and the battery) trickle charger.  Makes sense,
    but pretty pricey when you start buying them for a whole set of
    batteries...
    
    What led me to this discussion was an ad in the December '91 Model
    Aviation by Tejera Microsystems Engineering in Tampa, FL...
    
    	- Automatic switch to trickle after 16 hours
    	- "Reduces charger to pulse trickle"  (I have heard people say that
    		pulse trickling is better than constant trickle)
    	- Converts *all* overnight chargers with one unit..  Up to 30
    		chargers (120W)
    	- Use it for other battery powered tools
    	- $39.85 + $3 S&H
    
    What I gleened from the ad is that this unit plug in between the AC
    outlet and your chargers.  You can then plug, using extenstion cords or
    whatever, up to 30 chargers.
    
    So, what do you think the unit does??  Do you think it simply turns the
    AC power on and off at a regular rate, providing an interrupted
    standard charge rate??  Or might it reduce the AC line
    voltage/current/amperage (juice!) which in turn reduces the output of
    the chargers??
    
    Based on the answer to the above, would any of you h/w folks care to 
    take a stab at a design??  
    
    Cheers,
    jeff
    

RE: Note 790.81 by N25480::FRIEDRICHS
>    So, what do you think the unit does??  Do you think it simply turns the
>    AC power on and off at a regular rate, providing an interrupted
>    standard charge rate??  

    If it simply switches on and off the AC, buy what Watt (Charlie)
    suggested.  Just buy one of those timer "things" that plugs in to
    the wall outlet.  These are sold so you can plug in a light and
    have it look like someone is home when you're gone for vacation or
    whatever.  (Light turns on/off at specified times.)  Set it up for
    charging 4 hours per day.

    Of course, you still have to do an overnight charge after a flying
    session before hooking it up to the 4 hour timer...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    The 24 hour timer I have has a knob on the side so you can turn it
    on/off manually. If you turn it on during the off phase it will stay on
    until the end of the on phase (Reith-ese translation anyone?). With this
    timer I'd be able to select a 4 hour period to charge, 12 hours from
    the time I start it and it would initially charge for 16 hours and then
    4 hours every day thereafter. Is trickle defined as 5% of the batter
    capacity still or is it even lower? (25ma for a 500ma pack)

    I will call them later if I get a chance and try to find out what
    they really do..  
    
    I agree that the security timer (you can get them to turn on/off every
    15 or 30 minutes too) is the way to go if that is all they are doing..
    
    Any other speculation??
    
    jeff
    

    I have been using both the Light timer and a constant current trickle
    charge with good results.  I don't have automatic.  I put my stuff on
    normal charge rate overnight after flying and then switch it to trickle
    to be left indefinately.  The trouble with timers for charging is
    reliability.  If you get a power glitch, does it switch to trickle?  If
    so, you never really know if you got a full charge.  A safe design
    would switch to overnight charge rate on a power glitch - or even
    better, have a clock chip with battery backup.  Naah, I'll stick to the
    manual switch method - it works for me.
    
    Charlie
    

    
       I have been using Charlie's manual method for over a year, and I
    am quite happy with it. Although it does require minimum attention
    (to switch it back to the timer the next morning), it eliminates 95% of
    the hassles involved with having your batteries charged and ready to
    go.

I've been using the trickle charger devised by Charlie/Eric and whoever else
(Bill Lewis maybe) and it's been working great for me. It's five channels and
I have 3 RX and 2 TX hooked up. After a full day of flying, I simply hook
everything up the the trickle charger and that alone will charge everything
back up to about 80% capacity. The morning I'm going to fly, I'll just plug
everything into the charger for a couple of hours and I'm ready to go.

Actually, the 80% figure might be a little low. I can run my TX battery down
to say 9.6 volts and after a day on the trickle charger, it will ready about
11.2. A full charge reads 11.4.


Steve

    I recommend doing a real charge after flying before putting things on
    trickle.  That way you're ready to go and you don't have to remember to
    put things on charge before flying.  Other than the battery life
    benefit (which is hard to demonstrate), the main reason I trickle
    charge is to keep things fully charged and ready to fly.  A trickle
    charger will take a week to do any significant charging of a discharged
    pack and if it's a very low level trickle charger, it will take even
    longer.  During the flying season, I do all of my charging in my car. 
    I have a six channel charger that does full rate charging and trickle
    charging right in the back with my planes.  If I take a couple of lunch
    time flights, I put the plane on charge from lunch time until I go home
    from work and then switch it to trickle.  Works great for me.
    
    Charlie
    

    I've been playing around with the bare bones charger in .25 in the past
    and just noticed a slightly more complex circuit in the 1/92 Model
    Aviation. Anyone have any comments about how much better/worse this
    circuit is (it uses a specific light bulb for a current limiting device
    and a few other parts)

    
    
    
    
    Not sure which battery note to post this in, so I'll put it here. 
    Moderator, feel free to move it.
     
    I recently acquired an RK Electronics Rapid NiCad Charger to allow me
    to revitalize Tx and Rx NiCads at the field.  Upon reading the
    instruction sheet I discovered a CAUTION about rapidly charging NiCads
    if the manufacturer warns against doing this.  So I dutifully got out
    the manuals for my Airtronics and JR equipment and went through the
    fine print.
    
    Here is what I found.  Airtronics is mute on the issue of rapid
    charging the nicads in their equipment.  JR, on the other hand, is
    _very_ explicit about charging their batteries at only the C/10 rate
    provided by the stock charger!!  Apparently they are not supporting any
    rapid charging of the nicads they use.  This was a surprise, since I
    was expecting that this would not be a problem given the large number
    of RC'ers who rapid charge their nicads.
    
    The RK Electronics unit I bought charges at about 500 ma, which is the 
    rating of most of the battery packs I have.  I would think that this
    charge rate is not excessive or dangerous for our equipment, yet I am
    confused by JR's warning.  Can anyone shed some light on this?
    Has anyone else used a rapid charger on JR or Airtronics stuff?  What
    are the results, good or bad?
    
    Very curious on this one.
    
    Regards,
    Joe                     
    
    
    

    Hi Joe,
    
    	I have all JR equipment and a rapid field charger. I've used it
    several times. No problem. I will continue to use it. I believe JR
    is just being overly cautious because of some quirky TX charge setups.
    It's easy to reverse charge the TX if you don't make the necessary
    plug changes. Most chargers require you to attach your own plugs so
    JR is just covering their butt against people that get the polarity
    wrong. Go ahead and use it.
    
    Steve

    Joe,
    	Rapid charging of radio nicads should be avoided except when
    absolutely necessary.  I do it on occasion if I want to safely put in a
    couple more flights and my ESV says no.  I slow and trickle charge
    whenever possible.  JR uses the same Sanyo batteries that everyone else
    uses so theirs are no worse than others.  The AA nicads are just not
    designed for quick charging and it can shorten their life.  If the
    cells aren't matched then some get overcharged with almost any charging
    scheme.  This makes them hot and they outgass.  What I do when rapid
    charging is never try to do more than a half charge.  I will charge for
    20 minutes at 1 amp which is about 330 mah.  This prevents overcharging
    the lower capacity cells in the battery.
    
    Charlie
    

    Re, the last couple.
    
    Thanks for the advice.  Since this particular charger only charges at
    about 0.5 amp, my feeling is that it isn't as dangerous as the really
    high current jobs that do multiple-amps.  So, with the caution
    mentioned, I will give it a try and see how it goes.
    
    Appreciate the help.
    
    Regards,
    Joe

    Joe,	
    	As long as the nicads are fairly well discharged, you can charge
    them safely at .5 amps for at least a half hour.  That would give you
    about half of a full charge.  You could go longer if you're really sure
    the pack is almost discharged when you start.  Ues it only when
    necessary and you should not have any problems.  
    
    Charlie
    

    Well, I finally got a chance to try out the new charger I mentioned a
    few back.  One day, I inadvertently left the Tx switch of the Extra300
    on for about an hour.  When I discovered this, I took an ESV reading
    and foung the needle still in the green area, but low enough that I
    decided to do a quick field charge.
    
    I hooked the charger up to the car battery, plugged the charger into
    the Tx charging jack, saw the lights come on, and went off believing
    everything was working.  When I checked the battery about 25 minutes
    later, it had the same ESV reading as before, so I concluded it was
    either charging _very_ slowly, or not at all.  Let it go for another 20
    minutes or so, and the same reading again.  So now I'm thinking this
    thing isn't working, even though the lights are on.
    
    I wonder if JR systems (the entire flight package on this plane is JR)
    have a limiter to prevent fast charging?  I know all the polarities are
    correct, so I don't know what could be wrong.  
    
    ANyone have any experience with JR equipment exhibiting this behavior?
    
    Regards,
    Joe

    Joe,
    	Put an ammeter in the circuit and monitor the charge current. 
    That's the only way I know of to see if things are really working.  I
    don't trust an LED to tell me things are charging.  
    
    Charlie
    

    Which TX is it?

    Re: -.1
    
    The Tx is the X347 and the Rx is the NER327X.  I still havn't gone back
    over this due to lack of time, but I plan to repeat this as soon as I
    can.
    
    Is it possible for charge lights to come on even though no charging is
    taking place?  Or more properly stated, if a very small charging
    current was flowing, would it light the indicator light?  This might
    explain why the light was on but no fast charging was taking place.
    
    -Joe

    
    I have some questions about some nicads I just "acquired".
    
    I have 2 12volt 3.0Ah Nicads and 1 12volt 5.7Ah Nicad. I'd like to use
    them in my flight box (I think).
    
    Questions:
    
    1. Can I connect them in parallel, and treat them as 1 12v 11.7Ah
       battery? Can I then charge them together at (e.g.) 1 Amp for
       11 hours?
    
    2. Would they be OK to power a starter and a glow clip through a
       power panel? Or would the starter flatten them in double quick
       time?
    
    3. Should I stop being tight and go and *buy* a decent 12v battery?
    
    As always, any advice gratefully received!
    
    Thanks
    
    Nigel
    

    No - you should not connect two nicads in parallel - especially if they
    are different ratings or different ages.  However, a 5.7Ah nicad should
    power a starter just fine.  Make a charger and you're in good shape. 
    You should charge the 5.7Ah one at about .6A overnight for normal
    charging.
    
    I use 4 Ah 12 V batteries for my starter and it works great.  I use the
    same battery to run my field booster charger and I only charge it every
    other time I go flying.  I would prefer these nicads to a Gel Cell any
    day.  They are lighter and they are mush less fussy about being
    discharged.
    
    Charlie
    

    
    Thanks Charlie!
    
    I'll use the 5.7Ah for the starter, and use one of the smaller ones for
    running my glow supply.
    
    Cheers
    
    Nigel
    

    You will find that the Nicad will run your starter very nicely.  The
    internal impedance is less for nicads so more volts get to the motor.
    I assume your pack is 10 cells to get 12 Volts.
    
    Charlie
    

    What are folks using to charge their 1200mah receiver (4.8V) batteries.
    
    Dawn finally arrived over marble-head last night that charging my
    battery for the 1200mah Junkers battery at 50mah just is not going to
    cut it.
    
    Can I just go to radio shack and get a 4.8, 120mah output converter
    and use it??  I would prefer to not have to play with the electronics
    side of it as I need to charge this battery (and I want to cycle it 
    at least once before I fly...)
    
    Thanks!
    jeff
    

    
     I am just recharging my 900 and 1200 packs with the 50 mah charger.
    
     Worse case it takes 24 hours, and most of the time significantly
    less. Haven't had any problems so far. If I am in a hurry I charge it
    off my Litco cycler, which will give me a 90? mah charge.
                                                            

    
>    Can I just go to radio shack and get a 4.8, 120mah output converter
>    and use it??  I would prefer to not have to play with the electronics
>    side of it as I need to charge this battery (and I want to cycle it 
>    at least once before I fly...)

The 4.8V 120mah won't do it anyway. You need a voltage source of somewhere
around 10V to be able to push enough current into the battery. I can't
imagine something like that would be very difficult to construct.

Also, if you're using C/20 shouldn't you double the charge time to get
a peaked pack? That would give you 30 hours at 50ma.

Dave

    I made my own 120 Ma chargers - easy to do.  I have a 6 channel charger
    that will do 10,50,120 ma on any channel.  Tower has a nice 4 channel
    unit with the same capabilities for around $29.  It is well worth it.
    With that unit you can charge your TX, RX, Ni-starter, and Gel cell all
    at once at the proper rate.
    
    Charlie
    

    
      Jeff,
    
         If you order the unit from Tower, please order two. I will 
    gladly split the postage with you.

    Jeff,
    
        I use my Astro Flight charger set to 100 mah trickle charge.
    
    
    Regards,
    
    Jim

    I have tried using 50ma for 24hrs and then cyled the pack (Three times)
    and then used 90ma, ditto, and then 120ma ditto.
    The results were poor for the 50ma. I only got approx 800mah on each
    cycle. With 90 and 100 ma on 16 hour charges I got approx 1300mah each
    cycle.
    
    Deduce your own path from this.
    
    Regards,
    
    E.
    
    P.S. I used Digipace-1 chargers.

    I stopped by RC Buyers last night and Bob had one of the Hobbico
    4 channel chargers..  $29.95  (sold!)  Dan, he said he would be 
    getting another in a couple of days..
    
    It uses A/C power (only) and has 4 bannana plug sockets.  4, 3 position 
    switches.  2 of the channels do 10/25/50mah and the other two do 
    50/100/300mah (I think that was how they were divided up).  I feel 
    better about this now.
    
    Thanks!
    jeff
    

    Jeff,
    	I like the Hobbico unit and based on my own building experience, it
    is a bargain at $29.95.  It is  very flexible and can charge any number
    of cells because it is a current source charger.  One problem - if you
    turn the AC off and leave anything hooked up, it will discharge back
    through the charger.  To prevent this, you can install a diode in the
    leads.  I did this for a buddy that has two of these units.  He uses a
    light timer to run the charger 2 hours a day to "trickle" things.  It
    was discharging his batteries when the light timer was off.
    
    Charlie
    

    I'm glad you told me that!!  The diode goes in tonight!!
    
    I have a light timer that only turns off so I can set a 15 hour charge
    and not worry about over charging...  
    
    Thanks Charlie!
    jeff
    

    Jeff,
    	Just to clarify, you need one on each of the four channels.  You
    can just splice it in series with one of the leads for each channel -
    and make sure that it allows current to flow in the charge direction.
    When rigging up chargers be very careful not to reverse the charging
    polarity - or disaster can result.  It's easy to do and it can cost $$.
    &^%$ JR has reverse polarity on their TX jacks - center negative.
    If you reverse charge a nicad pack, it will blow your TX computer chip
    or destroy your servos and RX in your plane.  CHECK EVERYTHING VERY
    CAREFULLY!  This is the biggest risk when hooking up your own charging
    leads.
    
    CHarlie
    

    Message received... 
    
    Thanks!
    jeff
    

    
    
       I need some help regarding the ACE fast field charger I bought from
    Jack at the auction. He installed TX type jacks on the ends of 
    both charging wires because he has his reciever batteries converted to TX 
    type jacks on his planes. I tested voltage at both connectors, and they both
    showed 12+ volts.
    
       I do not have any instructions with it, so:
    
    1. How do I determine which jack to use for the reciever ( they both put
       out 12 volts )
    
    2. How do I know when the charging is complete? ( Does the little red
      light come on? Do I have to monitor it with a voltmeter? )
       
          
        I plan to use a Futaba female connector on the RX, and reverse the
      polarity on the TX jack to accomodate JR transmitters.
    
               Any help would be appreciated. I f I don't get anything from
      the file, I will give Jack a call.
    
                                                          Dan
    
    

I don't know about that particular charger but many are constant current and
will read the source voltage (12vdc) on a non-loaded meter.

            
      I found the answer to one of my questions in the Towers Mag. The
    charger with automatically charge RX, TX, or both siimultaniously. It
    will automatically cut back to tricke when batteries are fully charged.
    It will charge an RX pack to 85% capacity in about 1 hour.
    
      So, if I use my ESV to check voltage, I will be able to determine the
    RX jack?

Might I suggest US3RMC::"[email protected]"

    It does sound like they are constant current.  So, you should be able
    to charge either pack from either connector.  
    
    What *MAY* be different is the charge rate.  You need to put an ammeter
    in line with the charger to see if they are charging at different
    rates.  But again, I suspect not...
    
    I suspect that it is probably charging at something like 500mah which
    would be fast charge for either a Tx or Rx pack.  It also sounds like
    it has peak detection to shut it off at 85%.
    
    But then again, I am just learning about some of this stuff. Charlie
    is certainly the expert...
    
    cheers,
    jeff
    

    
         Thanks for the help. I think the Notes file has lost a lot since
        Charlie left! 

    Say, does anyone know where to buy electronics from?  Like logic IC's,
    D/As, A/D's, display drivers etc.  And don't say Radio Shack! I don't
    want to spend a small fortune for a few parts :^)...I'm interested in
    building a digital charging system with LED readouts for
    current/Voltage and neato buttons and dials for adjusting everything.
    
    Andy
    

    "around" is an awfully general term. Best place "around" is U-Do-It in
    Waltham (well somewhere out there on the 128 belt)
    
    Nothing much in the Worcester/Westboro area not that Active on Flanders
    Rd closed

    
      I think I am all set regarding the questions I had on the Ace FFC. I 
    looked at the new version they have at RC Buyers. On the new version one
    wire comes out of the case on each side ( on mine, they both come out the
    bottom next to each other ). The wires on the new version are clearly 
    marked as RX and TX, with the RX wire having another thin set of wires
    running along side it. Mine also has a wire with a thin set attached,
    so I was able to identify this as the RX wire.
    
      I soldered the connectors on, and will do a test charge on a spare
    nicad, before I stick it in the van for future use.
                                            

    
    Does anyone have any experience with the new "Alpha 4" battery 
    management system from Litco??
    
    From their ads in RCM, they appear to be a very versatile (1-12 cells,
    10 different charging/cycling "programs") unit.  But, being 
    so versatile, you can use it not only for RC, but all of your 
    household nicads (power screwdriver, flashlights, etc)
    
    It is a bit pricey at $199.99.  However, if there is an order for 
    3 or more, each unit would get 3 free connectors (a $20 "value" that
    probably costs $3 from radio shack :-(  That was the only discount as
    they deal direct and have no dealer discounts.  
    
    I am seriously considering putting one under the Christmas tree for
    myself, and I may be buying one for our Ambulance service.  So, if
    there is anyone else that wants in, please let me know...
    
    
    ------
    
    BTW - I have also been trying to get in touch with LR Taylor.  I still
    think that for the bulk buy price of $45/each, they were a great value, 
    but they appear to have disappeared... :-(
    
    cheers,
    jeff
    

    Oh, I should mention a few other features of the Litco system..
    
    120Vac OR 12Vdc operation (you can leave it in your car to trickle 
    charge stuff, or fast charge at the field)
    
    It is microprocessor controled with an LED display with help and error
    text messages (including bad cells, etc.)
    
    

    Jeff,
    
    	Don't have any first hand knowledge about the Alpha 4, but I have
    the Litco fast field charger and the Litco cycler. Both perform as
    advertised and have been trouble free.
    
    
    Steve

    Jeff, I thought LR Taylor unit had disappeared too, but this past week I saw
    their ad in either RC Report or MAN.  I'll try to dig it out tonight.
    
    -Joe

A friend and I bought ALPHA4s this spring and have been using them 
regularly.  I have use it to charge my 12v gell cell, ni-starter, all 
xmitters, and recv'r packs.  I also used it to cycle and charge my 
camcorder packs.   It is extremely versatile.  Its direct readout of 
capacity is a great feature.  Just this last weekend we took it to the 
field and used it to field charge a transmitter.  I wish it had 8 ports 
instead of the current 4 (everybody always wants more).  If it wasn't so 
pricey I would have a second one already.

    Thanks for the input!
    
    BTW - I finally got a hold of LR Taylor last night.  Yes, they will
    do repairs and yes they are still actively selling them.
    
    The list price is now $99 though, and in a quantity of 12, we can get
    them at $75 each.  If there are folks that would rather have this
    unit, I would be happy to put it together since I have worked with
    them before.
    
    Personnaly, though, I think the versatility of the Alpha-4 makes it
    a much better deal...
    
    cheers,
    jeff
    

    I have the Alpha 4
    
    Simply put "I love it!"
    
    Two of my buddies have sold their Digipaces (as I did) and got one. 
    They appear to be as pleased with them as I am.  
    
    I use it for more than RC also.
    
    In fact another buddies wife called me up two days ago and wants me to
    order it for her as a stealth Christmas gift for him.  
    
    I highly recommend it!
    

    
    I will be ordering from Litco this week...  If I get 1 (or more)
    additional people (I currently have 2), then we can each get some
    wires/connectors for free.  They are not worth that much that I am
    going to postpone the order trying to dig up folks though...
    
    Corinne says that I can't use it until after Christmas though and that
    as soon as it arrives, I have to give it to her to wrap :-(
    
    If you want one, please let me know...
    
    Cheers,
    jeff
    

I'm going on a camping holiday in a few weeks time and I'd like 
to take my fast electric boat with me. I'll have access to 12V 
DC (my car!) and I'd like to trickle (not fast - I'm covered for 
that) charge my boat batteries (7.2 1200mah to 8.4 1700mah) from 
12V. Do I need to buy a suitable charger or can I put something 
fairly simple together myself? Advice and suggestions much 
appreciated.

Keith.

P.S. If I've missed this somewhere, a pointer would be 
appreciated.

OK, so I missed reply .25 ;-)

Taking that circuit as the basis, I put together a circuit 
to charge 4 packs simultaneously, complete with LEDs to 
indictate connection to power source and charge in progress. 
The only mistake I made was to put too small a diode in for 
reverse polarity protection which caused problems when I 
tried to charge more than one pack at a time. The whole lot 
went into a neat little box and as this is my first project 
which hasn't come straight "off the paper", I'm really 
pleased with it!

Keith.

        Just bought a Digipace 3 - nice unit but I'd have to question the
        operational parameters - 600mAh pack after two cycles shows 664 mAh
        capacity. 
        
        Andy
        

    
         Thats not unusual. Depending on the specific pack, they often will
    spec out at a higher mah than what is idicated on the battery. The
    important part is to document the number and then use it for comparison
    purposes when you cycle the pack periodically in the future.
    
    

        Looks like it, Dan - four cycles and it's consistently around 660
        mAh. If anyone is looking for a cycler, RC Buyers Warehouse has
        the (new) Digipace 3 for ~$119 - nice unit.
        
        Andy
        
    

    
     I have put together some 6 cell SC batteries to run my camcorders.
    I got the Radio shack 7.2 volt chargers for over night charging, but
    I sometimes need to charge 10-12 packs in about 6-8 unattended hours. 
    I thought a higher out put charger would work ( about 400mah ) but 
    can not find any 7.2 volt 400mah chargers. I also tried to parallel
    charge 10 packs together using a peak charger at 1.3 amps but killed
    one pack and the peak charger.  Any thoughts on where to fine a higher
    out put charger or some gang charger that will charge in 6-8 hours.
    Note ! The digapulse will not work. It takes 16 hours for only 6 packs.
    I also would like to keep the cost as low as possible. Maybe under $10.
    per pack.

    Thanks  Bob