Conference vmszoo::rc

    Not all NiCad cells are created equal.  The Sanyo cells are typically
    regarded as the best while others may or may not be as good.  

    My personal rule of thumb is "you get what you pay for" when it comes
    to buying batteries.  Since I'm into electric flight and need every
    electron I can get, I buy the "best" (usually most expensive too)
    batteries I can.

    On the other hand, if all you are interested in is a pack for your
    car to run around your back yard (and not competitive racing), then
    the lest expensive pack is your best bet.

    Note that I'm not saying there is always a direct realtionship
    between cost a quality of the pack.  After all, maybe Sears has a
    contract with Sanyo for a Zillion batteries and can sell the "best"
    packs for the least price (but I doubt it...).  

    As usual, what you want to buy depends on your application.  
    (Buy a Yugo to drive to the grocery store and a Porche to race
    professionally...)

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

    Ok  I just sprung for  Mr Pringles which is a twin .05 powered electric
    boat.  Now I need batterys and Im not sure what to get.
    I know that I need 6 cell but thats about it.  What's the difference
    between cadnica Sanyo red vs yellow vs billybob brand. what about
    matched set's and bla bla bla. also whats a good price.
    and also I see indications SCR, SCE
    
    Any help would be appreciated
    
    Dave
    
    

    I can give you some info based on our experience in RC cars...
    
    We have 3 types of batteries currently in use.
    
    SC, SCR and SCE, all Sanyo.    Most of the other brands on the market
    seem to be Sanyo batteries, just packaged or matched by the supplier.
    Panasonic is also on the fringe as a battery supplier to RC cars,
    but I havent seen anyone running them in competition so I assume
    they are not as advanced as the Sanyo product. I know Panasonic has
    the SC size in E and R/P types, but the prices seem expensive in
    bulk compared to Sanyo. In the following I will only speak to Sanyo, 
    except where noted.
    
    The SC battery is pretty good for general use. They are very durable,
    and can be recharged as often as you like in a day without having
    any real effect I have seen.  These batteries are usually not matched
    and are sold at modest prices (cheapest of the 3 types).  We are able
    to peak charge these OK, but the peak isnt as clearly defined as the
    SCR or SCE, probably due to the lack of matching.  We also do not
    cycle these packs to near zero for fear of permantly reversing a cell
    (again dure to the fact that they are not matched).  As far as
    performance, the SC does not provide the accelaration of either the
    SCR or SCE, and the slope from where they start to drop to where they
    will not move the car is very gradual, which gives us just about as 
    much total operation as the 1700mah SCE, but at lower performance 
    levels. Total run time in a stock legal car is about 7-8 minutes.
    The Billy-Bob (as you put it) batteries (Radio Shack, and the so
    called sportsman class) are about equivilant to or may be the Sanyo 
    SC.
    
    The SCR battery, a 1200mah capacity high current unit, is usually 
    purchased matched, but is available in bulk. The Sanyo shrink vinyl
    insulator is red on these type ni-cads.   I recommend you either 
    buy matched sets or set yourself up to be able to match them.  This 
    battery peaks at a lower voltage than either the SC or SCE, but ours 
    have a very dramatic peak, which is probably characteristic of both 
    the battery and the matching done by the suppliers. It also provides 
    the most speed and acceleration of the three types. We store this 
    battery with a 25 ohm resistor connected, per the recommendations of 
    Trinity.  The SCR is our pack of choice when running so-called "stock" 
    motors. In competition we get more than 4 minutes of operation and can 
    usually operate 5 minutes in off-road competition before the battery 
    dumps.  Dumping is a term which describes how an SCR transitions from 
    full performance during discharge to no performance.  The term also
    applies to the other types but it is most dramatic in the SCR.  When
    the battery dumps the car goes from full speed operation to a complete 
    stop in about 1 lap.  Because of that characteristic I would think they 
    would not be the best choice for boats or planes (unless other 
    considerations make this sudden drop OK).  One nice thing about these 
    batteries is that they are very rugged.  We have run a single pack thru 
    3 cycles in one afternoon without any noticable loss of battery performance.
    
    The SCE battery is a 1700mah high capacity unit. The shrink vinyl 
    insulation is yellow on this model.     It is also available in matched
    sets or in bulk. This battery is fairly delicate compared to the SC
    and SCR.  The suppliers do not recommend use more often than once
    per day or once per week, depending on who you talk to.  They are
    popular batteries in racing classes where re-wound motors are used.
    The extra available energy permits operation for the 4-5 minutes
    per race needed with the additional current demand of a higher
    performance motor.  One also finds these in 7 cell configurations
    in open class cars, where the 6 cell SCR is the norm (6 cells is
    max allowed) in stock classes.  The 6 cell SCE pack we have used on 
    the stock motor will run about 7 minutes or so at competitive levels
    but not permit as much acceleration as the SCR.  The SCE peaks at a
    higher voltage than the SCR and can be peaked 3-4 times before use
    to pack as much energy as possible into the battery.  The SCR doesnt
    seem to gain much with second or third peak charges. It doesnt dump
    as steeply as the SCR either.  This would seem to make it the high
    performance choice for boats or planes assuming you can put together
    several packs so you dont need to run any single pack often. We also
    store this pack with a 25 ohm battery across the leads. The matched SCE 
    is usually the most expensive of the 3 types.
    
    To make this even more interesting, some suppliers offer grades
    within the SCR and SCE types.  This is generally a sort by actual
    mah demonstrated versus the nominal spec (1200 or 1700).  Obviously,
    the higher mah within a type would perform better/longer and will
    cost you more.  I have seen a couple ads for 1400 and 1500 mah SCR
    types, which is just a selected, matched bunch of 1200mah spec units
    on the high end of the bell curve.
    
    The above is fairly non-technical, and comparative. I hope it helps
    you differ between the common types and select the right ones.
    
    Walt

    
    re: .12
    
    	I would generally agree with Walt with the exception of the use/
    	value of the SCE's. We run 4-cell 1/12 modified for 8 minutes.
    	In this application we are seeing about a 30% increase (around 8 min
    	vs 6 min) running time with SCE vs SC (high quality, matched sets).
    
    	I have been told that this configuration (light weight, high revs
    	ie light loading) is what SCE's like. You cannot seriously compete
    	in this class where I race with anything but SCE's, at least not
    	for more than 6 or so minutes.
    
    	Chris
    

    RE: .13

    It is true that the SCE's do like a light loading.  They are not
    good for high current (heavy loading) applications.  As long as
    you're drawing less than 15 or 20 amps, the SCE's are fine.  Over 20
    amps, the SCE's heat up too much due to their higher internal
    resistance.

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

    Re. .12 (Walt Clark)
    
    Thanks a lot, Walt, for sharing your battery experience with us.
    I used to fly electrics about 8 years ago, and my knowledge about
    NiCads is rather conservative. I haven't managed yet to get through
    all the battery stuff in this notes file, and your overview was
    a great help for me.
    
    I just bought a fast charger for my flight packs (6-cell SANYO SCR),
    and the store owner seemed to know lots of things about batteries
    I never heard of before. One amazing thing was a method of formatting
    battery packs: Not by charging them with C/10, but discharge them
    to 0 V and then fast charge. He said that these new cells are designed
    for fast charge, and that's the best I could do for them.
    
    Now I read in your reply that you store the batteries with a 25
    Ohm resistor on them. This means they are stored deep-cycled, at
    0 V, true? Doesn't this harm the battery? I had learned to never
    deep-cycle them. How long do you store them with the resistor? For
    days, weeks, even months? How do you charge them after storage?
    Fast, or trickle charge? Please share some more experiences of how
    to maintain nowadays batteries, especially SCR's.
    
    Thanks and regards,
                        Hartmut

Wanted one orphaned large single nicad cell.

I have an on board ignition that is probably what
you call a sub C cell.  I want more capacity.

Anybody have an old cell left over from some pack 
that died?  If I can't find a orphaned free one
in the notes file then I guess I have to try get one
from the local radio shack - I'd like a D size but
I'll bet that SR packs a lot more amps into a cell than
Radio Shack.  What is the shipping charge on one cell?

Summary - I'm begging for a gift from your spare parts
bin.

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

    
    I just went from 6 cell to 4 cell racing...I have a few Sanyo sub C's
    of the SC variety (1200 mah).
    
    Is this what you're looking for?
    
    Send mail.
    	
    Chris

    KAY,
    
    If you can wait a few days for interoffice to get to you, I can
    let you have an unused, Gould "D" size 4 amp hour cell. Charge rate
    is 1/10, or 400 mils.
    
    Price = 1 cup of coffee, payable if we ever meet.
    
    don

    RE: .15
    
    We leave the resistor on the battery pack the entire time it is out 
    of use.  These are matched packs.  The company which matched them and
    sells them (Trinity) suggests this approach.  Another note on ni-cads
    also suggested this may help reduce or eliminate a problem where
    matched cells become un-matched after several cycles when deep
    discharging is not done.  If unmatched cells are done this way it
    is likely that one or more cells will reverse premanently caused by
    the stronger cells reverse charging the weaker one which goes
    to zero first.
    
    I am not an expert by a long shot.  I just started learning the
    details of ni-cads this summer when my son started racing cars.
    
    Walt

    
      Re 643.12
    
         What are the maximum number of cycles recommended per day/week
      for each of the 3 battery types; SC, SCR, and SCE ?
    
         Also, what determines the number of recommended cycles, ie;
       a SCE pack should only be cycled once a day/week ? Do the batteries
       have to re-equalize or does it pertain to heat ?
    
                                                  Dan

                                                  Dan

    
    	I've been told by the retailer and distributors that SCE's should
    	be used/cycled once per week. It sounds extreme but at the going
    	rates ($10-16 per cell) I'm doing what they say. Charging/peaking
    	rate of SCE's should not exceed 3.5 amps. 
    
    	I've been told that SCR can be generally abused and peaked as high
    	as 9 amps.
    
    	I've always held my SC's to once a day max and have gotten good
    	results.
    
    	Chris

>    	I've been told by the retailer and distributors that SCE's should
>    	be used/cycled once per week. It sounds extreme but at the going

    They just want to sell you extra packs.  Unless you're racing in a
    situation where every single last electron matters, you're just wasting
    your time.  There is no mention of cycle times in any of the NiCad
    applications books I've read, except that most manufacturers say that
    you can charge/discharge as often as you'de like, so long as you provide
    for adequate cooling of the batteries.

    SCE's are built with the same technology as SCR cells.  The primary
    difference, if I recall, is that the internal insulating walls in the
    cell are thinner, to allow room for more electrolyte.  This causes the
    cells to be more susceptable to damage from overheating, since the
    thinner material is more easily ruptured under the expansion forces
    created by the heat.

    Sanyo application engineers I spoke with said that the SCE's can be used
    in exactly the same fashion as SCR's, except that current draw should be
    limited to under 20 Amps, worst case.  Unless they've decided otherwise
    quite recently, this should still hold true.

    I only give my packs the opportunity to cool before I recharge them and
    go again.  I have yet to notice any degradation in current delivery, or
    duration.  I use both 6 and 7 cell SCR and SCE packs.  I usually peak
    charge.  Sometimes I'll just do it by how warm the pack feels.  You can
    charge a cell at any rate you'de like, so long as you cut off the charge
    when peak is reached.  GE applications says that the peak is more
    pronounced at higher rates of charge.

    There might be a variable that you touched on in .22 which would change
    the "recommended" usage rate of an SCE.
    
    In most of the local RC car competition, the open classes run for
    3 and 4 minutes. These cars usually exhaust the batteries in this
    time, and they all run SCE types.   This means they are averaging
    25-34 amps during the run, a some of this obviously consumed
    by the internal resistance of the cells as evidenced by the warmth
    of the cells at the end of the heat (no pun intended by me). 
    
    Given the 20 amp max recommended by your Sanyo rep, the extra heat
    caused by the high demand of some of the racers, and the lower
    strength of the SCE cell (thinner walls?), there might be some
    basis for the once-per-day, and/or once-per-week suggestions other
    than a desire to sell more cells.
    
    Walt

    The cell of an SCE is physically more fragile than an SCR, so you do
    have to be more careful of heat, but if you allow the pack to cool
    before you recharge it, it shouldn't matter how frequently you actually
    charge. 

    This leaves chemistry as the only reason for specifying a longer
    interval for the cycle.  Since the SCE and SCR cells use the exact same
    chemistry, they should behave the same when charged/discharged, except
    that the SCE will get hotter under a given load.

    It's possible that the cell chemistry requires some "recovery" time,
    since electrolyte, as well as electrons, migrate around in the cell when
    it's being charged and discharged.  Regardless, I don't see how they can
    spec a once/week cycle.  These batteries were designed to provide high
    current, fast recharge repetative cycles (in things like emergency
    medical equipment, etc.).

    I'm not an expert, by any means, but the info you're getting seems too
    extreme, and at odds with the design criterea and manufacturers
    specifications for the cells themselves.
    

    
    
    	This month's Competition Plus has an article dealing with some
    	recently ROAR approved batteries as well as an update on SCE's.
    	On the section dealing with SCE's they say...
    
    	"The one thing that has not changed is the charge rate for these
    	 cells, don't exceed 3 amps and let these cells rest 48-72 hours
    	 before recharging and using them."
    
    	I know, don't believe everything you read.
    
    	I'm turning my charger down to 3 amps until I read something
    	better.
    
    	Chris

    
    
         The reason I had requested additonal information around the
      number of cycles/day or week was to confirm what I was told at
      Hobby etc. in Nashua, as well as the comments in .12. The person
      at Hobby etc. confirmed the maximum of 3.2 amps for recharging,
      although he did not specify the reason. He also recommended maximum
      1/day (Preferably 1/week) cycle for the SCE's. He said it was
      due to the chemicals (Electrolyte) needing time to stabilize.
                           
         As the new owner of a matched 7 cell SCE pack for use in an
      airplane, I would like to use the pack as often as possible 
      without damaging the pack or shortening its life, as it allows
      a critical couple of extra flight minutes.
    
         It will be interesting if the facts can ever be separated from
      the wife's tales.
                                                       
                                                         Dan

Panasonic has a new battery that is supposed to be SCE capacity with SCR 
durability.  I have two (6-cell) packs of these batteries used in a
1/10 scale On-road (TRC PRO-10) car and I treat them just like my SCR packs,
9 amp charge, multiple uses per day, etc. and they are holding up just fine.

They don't quite have the "punch" of an SCR but do have about a 1500mah 
capacity.  Although I have the equipment to match cells, the person who 
sold me the batteries told me not to bother because the cells vary enough 
from charge to charge that matching would be a waste of time.  If that's 
not true, then a matched set of these batteries could rival the SCE in charge
capacity without all of the (aledged) kid-glove treatment requirements.

    
                     Nicad charging question.
    
      I am requesting someone with more nicad experience than I to help
    me with the following contradiction about cycling/charging:
    
       I have read that nicads should not be discharged below 1.1 volts
    per cell. So if I was charging A 7 cell pack, I assume that 7.7 volts
    indicates a discharged condition.
       My newly purchased Astroflight charger indicates the pack should
    be discharged to 1 1/2 amps before charging. When the pack gets down
    to 1 1/2 amps, the voltage has usually dropped to 2 volts.
       I have been discharging down to 1/12 amps/ 2 volts with no known
    problems. My questions are: 
    
             1. Am I risking damage to the pack ie; cell reversal?
    
             2. Any idea why the conrtadiction in advise?
    
    
                                      Just wondering,
    
                                            Dan Weier
    

    Some one else will have to answer the low current limit aspect of
    the question, but I think I can say why 1.1 volts per cell is magic.
    
    It isn't.  It is simply a good value that is easy to remember and
    with enough margin to be user friendly.
    
    The voltage vs charge [or time] curve for a NiCd drops off its plateau
    precipitously.  So first, the amount of energy still left after the
    drop has really started is relatively little --- there is naught to be
    gained by letting it drop below 1.1 or thereabouts.  Second, in a rapid
    discharge situation (e.g. a few Amps), there is little time margin
    between the knee of the curve and when a particular cell in the pack
    may have reached its zero point.  So you would be squeezing at risk for
    little return. 
    
    There is a rationale for a particular stop_voltage.  If you stop at 1.1
    volts per cell for partially discharged packs of twelve cells or less,
    you can be almost absolutely certain that no cell is yet at zero.        
    [ (N-1)*1.2 = N*1.1  ---> N=12 ]  This isn't so if the other cells
    are fully charged (the basic contributions are higher).  If there
    are fewer cells, this assurance is at a lower voltage than 1.1 (e.g.
    0.9 for a four cell pack --- it ain't worth it).

    Some of the NI-CAD users here in Europe totally discharge their
    packs to 0. They even stock them in that condition with a 50 ohm
    resistor connected between flying sessions. They recharge them using
    exclusively fast charging.
    
    This method has the reputation to give very solid packs, specially
    for high or very high current application.
    
    However you should not alternate this method with another one.
    
    I have done it on a couple of packs to test it. It gives indeed
    very predictable and strong performance. I did not experience any
    problem yet.
    
    Regards
    
                                                                  
    
    

    The 1.1 V/cell rule is, as stated, just to provide some margin.  The
    problem with discharging packs is cell voltage reversal.  You don't want
    to have one cell in the pack reverse charged by the others as they
    discharge.  Thing is, SC and SCR packs can withstand indefinite periods
    of low-current (C or less) reversal without any harm at all.  I usually
    discharge my packs till they show less than 1 amp.

    Charging packs in parallel is dangerous because you can't easily tell
    when one pack is charged and the other isn't.  There's no way to assure
    that both packs are at the same level of discharge. If you're trying for
    a 90% charge, you could easily end up overcharging one pack, and
    undercharging the other.

    If you have well matched cells, you can fully discharge the pack
    without damaging the cells, but you must be sure that the pack stays
    balanced.  THat's why people store them discharged rather than charged.
    All cells self discharge if stored charged, but not at the same rate,
    so your pack will get unbalanced if you store it charged.  A better
    alternative is to store it on trickle charge at .01 to .03 C.  That
    way, your pack is charged and balanced when you want to use it.  You
    also do not want to fast charge an unbalanced pack because some of the
    cells will go into overcharge before the others have fully charged. 
    Overcharge is what ruins NiCads!  They get hot and vent out the safety
    vents or explode if the vent don't work.
    
    Charlie
    

    I just read an interesting post on rec.models.rc.  Basically, the C/10
    charge rate used by those tx/rx chargers is safe for the batteries for
    an indefinite amount of time.  This seems to imply that C/10 is the
    tricle rate for NiCd's.   Apparently, this was verified with the Mfg. 
    Any thoughts?
    
    andy
    

   Well, if you go back and read notes in here, Al Ryder talks about
   C/10 being safe for indefinite charges a number of years ago.  He did
   a fair amount of research on the subject.
   
   To summarize his findings though...  Heat is the major problem.  If the
   batteries get too hot, they vent and you lose battery potential.  Heat
   can be generated by charging (like at a "C" rate), but it is also,
   obviously influenced by external temperatures as well.
   
   The C/10 rate will not, in of itself, generate enough heat to vent
   cells.  However, it is not far below the line either.  If the battery
   is kept in a cool (not cold) area and well vented, then yes, it should
   be fine.  Enclosed in a plane sitting in your car all day??  Dunno.
   
   The other problem is maintaining a C/10 rate.  Although that may be what
   the charger is nominally designed to, it will be different depending on
   the house voltage.  Soo, if your house power is at 125Vac, then you are
   probably charging faster than C/10.
   
   So, no, C/10 is not trickle charge, but yes, under the right conditions,
   batteries can be charged indefinitely at this rate.
   
   Personally, I would love to have 2-3 more Litco "Alpha-4" battery
   systems.  At least I can keep 2 transmitters and 2 batteries on it all
   the time at real trickle rates and not have to worry..
   
   Like I said, Al, and Charlie Watt go much deeper in other notes..  Good
   reading if you care about your batteries..
   
   cheers,
   jeff