Conference unifix::sailing

    No problems at all.  We do it with three batteries and save a fourth
    to start the engine.  One hint.  If you do it,  try to limit the
    time between when you turn your battery switch to "Both" and when
    you crank your engine if the bank of two batteries is dead.  If
    you wait too long you will find the good battery has drained its
    power into the dead batteries with noe of them good enough to start
    the engine.
    

Batteries should NOT be permanently connected in parallel. Parallel 
connection will work for a time, two or three years perhaps. However, 
there will be a slow deterioration of the battery plates due to small 
recirculating currents between the two batteries. Eventually, a cell in 
one battery goes bad. The charging system charges, but the bad cell 
takes all the current, and the remaining good cells do not get charged. 
The final result is that both batteries are destroyed. If a cell in one 
battery shorts, the good battery will discharge into the battery with 
the shorted cell, possibly causing enough heat to start a fire. 

If you want more battery capacity, install a third 12V battery and a 
second battery switch (a high quality Cole-Hersee vapor-proof switch is 
$40 discount). Or, better, replace one 12V battery with two 6V batteries 
in series. Unless you also install a larger alternator, your total 
engine running time to recharge your batteries will stay the same.

Finally, do not reserve one battery for engine starting. If the engine 
starting battery develops a bad cell, it quite likely will start the 
engine once when the engine is willing to start. It won't crank the 
engine very long. But you won't know this until too late. For optimum 
battery life, about half discharge the battery, start the engine with 
it, recharge fully, and then change to another battery and repeat the 
cycle. This will maximize battery life and allow you to detect a failing 
battery.

For information about sophisticated battery charging systems, contact 
Cruising Equipment, 6315 Seaview Avenue NW, Seattle, WA 98107 or Ample 
Power Company, 2442 NW Market St, Seattle, WA 98107. A really good 
system for a boat with modest electrical needs is around $1500.

Alan

       Remember also that when the battery switch is in the "Both"
    position, they are in fact being connected in parallel. Thus, if
    you leave the switch in this position while your boat is at its
    mooring, you run the risk of the battery damage/drainage described
    by Alan (.2).
    
       I think a properly installed battery isolator will dissipate
    any concerns of one battery discharging or damaging the other. This
    would allow you to easily parallel two batteries on one side of the
    battery switch. (Although the isolators aren't advertised as being
    used in this manner, I don't know of any reason why it wouldn't
    work.)
    
       You should also have some sort of battery charge indicator as part
    of your electrical system. I'm not talking about the little gauge
    that you probably have in your console now, that is more an indication
    of how the alternator is doing than the batteries. Rather you need
    something that can selectively test either battery while the engine
    is off, and will give you an indication of how fully charged the
    battery is (typically via an LED bar graph or RED-YELLOW-GREEN lamps).
    
    
    Frank
    

    Shoot, this is all news to me.  I've been doing the parrellel routine
    for some time now and have had no problems.  The one part I disagree
    with is the part about having a seperate battery to start the engine.
    I know it's better to run batteries down and charge them than to
    leave them fully charged, so we change them around once a month
    or so, giving the starting battery a chance to cycle.  
    
    We use the bank of three for instruments and also lights during
    night races and passages.  It's not always convenient to run the
    engine a lot and sometimes the batteries run down enough to kill
    the instruments.  At these times it sure feels good to have an isolated
    battery for the engine crank.
    
    Another point.  Someone said that to do it "right" would cost $1500.
    Seems to me that I could afford to replace my batteries every two
    or three years for that.  Batteries won't last much longer than
    that anyway.  
    
    Am I way off base here?
    
    Dave

re .3:

There are three problems with using a diode battery isolator to prevent 
paralleled batteries from discharging each other. 

First, there is a significant voltage drop across the diodes (typically
0.7V). This, in effect, makes the battery appear more discharged than it
really is. 

Second, the diodes are rated for some low current (say 50 to 100 
amperes). The current drawn by the starter motor for a small diesel 
(25 hp) is on the order of 250 to 300 amperes at stall. This will 
almost certainly destroy the diodes in the isolator.

Third, a good isolator costs as much or more than a good battery switch.

Yes, the most convenient way to determine the state of charge of a 
battery is to measure the voltage. However, the voltage only represents 
the state of charge after the battery has been unused (no current drawn) 
for about 24 hours. And the voltage must be measured accurately to 0.1 
volt or better (0.01 ideally). Digital panel meters reading to 0.01 volt 
are available for about $70 from electronics supply companies (eg, 
Newark).

re .4:

The cost tradeoff between a sophisicated charging system and replacing 
batteries isn't clear at all. High quality deep cycle batteries are 
over $100 for a 12V 105 Amp-hr battery. Four batteries replaced every 3
years is $100 per year. The life of the same battery in the
sophisticated system is over 10 years (the price I quoted includes
batteries). Plus, with the sophisticated system charging time is reduced
(the typical automotive-type alternator on marine engines is far from
the optimum battery charging device and simply using a high current 
alternator is only a partial solution) and the reliability of the
electrical system is increased. Frequently discharging your batteries to
the point where they won't start the engine will ensure them an early
death. And while they are dying their capacity is being steadily
reduced. I was surprised to learn how difficult it is to keep batteries
in good condition and to ensure long, reliable life. 

I haven't yet installed a sophisticated system, but it is high on my 
list of improvements to my boat. The compenents of the system are easily 
removed and reinstalled in your next boat.

Alan

    SORRY FOR THE ABOVE, BUT I WAS GETTING A BROKEN LINK.
    
    I'VE HAD MY BOAT 8 YEARS, LIVED ABOARD 6 YEARS AND CRUISED MEXICO
    AND THE SOUTH PACIFID 1 &1/2 YEARS.  I KEEP MY STARTING BATTERY
    COMPLETELY ISOLATED FROM THE HOUSE BATTERIES EVEN WITH ITS OWN VAPOR
    PROOF SWITCH. (OF COURSE, I ALSO KEEP A PAIR OF BATTERY JUMPER CABLES).
    I FEEL THAT IT IS IMPORTANT TO KEEP THESE BANKS TOTALLY ISOLATED
    FOR ONE ANOTHER.
    
    THE STARTER BATTERY IIS REQUIRED TO DELIVER A SHORT BURST OF HIGH
    AMPERS AND THEN BE RERCHARGED, WHILE THE HOUSE BATTERY IS REQUIRED
    TO WITHSTAND A SLOW DRAIN (DEEPLY) AND THEN RECHARGED.  BECAUSE
    OF THE DIFFERENT REQUIREMENTS THESE TWO TYPES ARE DESIGNED DIFFERENTLY.
    
    A GOOD SOURCE FOR HOUSE BATTERIES ARE "GOLF CART" 6 VOLT BATTERIES
    TIED IN PARALLEL.
    
    BESIDE COST, THE DIFFERENCE BETWEEN "MARINE" AND" AUTOMOTIVE"
    ALTERNATORS IS THE RUNNING OR CHARGING RPM.  SINCE A MARINE ENGINE
    RUNS AT A SLOWER RPM THE AUTOMOTIVE TYPE ALTERNATOR NEVER REACHES
    ITS CHARGING CAPACITY.  A SOLUTION TO THIS IS TO REPLACE TH ALTERNATOR
    PULLEY WITH ONE OF SMALLER DIAMETER.
    
    I'M PRESENTLY INSTALLING "PREVAILOR" (NOT SURE OF THE SPELLING)
    BATTERIES. A NEW TYPE OF BATTERY FROM GERMANY THAT HAS "GEL" INSTEAD
    OF WATER.  THE ADVANTAGES ARE: TOTALLY MAINTENANCE FREE, NO HYDROGEN
    DURING CHARGING, CAN OPERATE AT ANY ANGLE - EVEN UPSIDE DOWN, NO
    ACID SPILL, CAN OPERATE UNDER WATER ETC.
    

re .7:

>>>    THE STARTER BATTERY IS REQUIRED TO DELIVER A SHORT BURST OF HIGH
>>>    AMPERES AND THEN BE RERCHARGED, WHILE THE HOUSE BATTERY IS REQUIRED
>>>    TO WITHSTAND A SLOW DRAIN (DEEPLY) AND THEN RECHARGED.  BECAUSE
>>>    OF THE DIFFERENT REQUIREMENTS THESE TWO TYPES ARE DESIGNED DIFFERENTLY.
    
True enough. However, a deep cycle battery is quite capable of supplying 
enough current to start the typical small diesel with no problems. 
Automotive batteries have much less lead and much weaker construction. 
They shouldn't be used aboard boats. Since a deep cycle battery can 
supply engine starting current, why bother with a dedicated engine starting 
battery, especially one of different design?

>>>    A GOOD SOURCE FOR HOUSE BATTERIES ARE "GOLF CART" 6 VOLT BATTERIES
>>>    TIED IN PARALLEL.
    
I'm sure you mean in series.

>>>    BESIDE COST, THE DIFFERENCE BETWEEN "MARINE" AND" AUTOMOTIVE"
>>>    ALTERNATORS IS THE RUNNING OR CHARGING RPM.  SINCE A MARINE ENGINE
>>>    RUNS AT A SLOWER RPM THE AUTOMOTIVE TYPE ALTERNATOR NEVER REACHES
>>>    ITS CHARGING CAPACITY.  A SOLUTION TO THIS IS TO REPLACE THE ALTERNATOR
>>>    PULLEY WITH ONE OF SMALLER DIAMETER.
    
This really depends on the alternator and the speed of your marine 
engine. Most alternators will reach maximum output at an engine speed of 
about 1500 rpm. The problem with most alternators is that their output 
falls drastically with increasing internal alternator temperature. The 
typical automotive alternator will only deliver its rated output for a 
few minutes before overheating. Alternators designed to deliver full 
output indefinitely are much more expensive.

>>>    I'M PRESENTLY INSTALLING "PREVAILOR" (NOT SURE OF THE SPELLING)
>>>    BATTERIES. A NEW TYPE OF BATTERY FROM GERMANY THAT HAS "GEL" INSTEAD
>>>    OF WATER.  THE ADVANTAGES ARE: TOTALLY MAINTENANCE FREE, NO HYDROGEN
>>>    DURING CHARGING, CAN OPERATE AT ANY ANGLE - EVEN UPSIDE DOWN, NO
>>>    ACID SPILL, CAN OPERATE UNDER WATER ETC.
    
Operate under water? Not unless you totally waterproof all the
connections (which is very, very difficult). Salt water is an excellent
conductor. These batteries also cost much more (about 50%?) than
conventional batteries. The hydrogen and oxygen released during charging
conventional batteries can be converted back to water by Hydrocaps (a
catalytic device -- some $10 to $15 per cell). 

    re .7
    
    Don't depend on the gel cells to work for long in the application
    you're considering.  They are very sensitive to overcharging.  If
    you overcharge them they vent and don't have any spare electrolyte
    to lose.  
    
    We use sealed lead acids in battery backups here at DEC, and see
    a lot of overcharge failures.

    re .7:
    
    Alan,how many years of service do you expect to get out of your deep
    cycle batteries ? What is your record so far ?
    
    Just interested.I'm using the cheapest automotive batteries available
    and had no problems so far.
    
    Peter

re gel electrolyte batteries: 

These are the way to go if money is no object -- the one USA price I've 
found is $400 (yes, $400) for a 100 A-hr battery. But:

	estimated life is 8 to 10 years

	can be recharged (guaranteed) after being shorted for 30 days 
	(no conventional battery will survive such treatment)

	maximum discharge current 770 A


re life of conventional batteries:

Properly maintained and recharged, life can be 10 to 15 years. 20 years 
is not unknown. Even though I have only the standard marine alternator 
charging system, the original deep cycle batteries in my boat lasted 
five years. My present three year-old Surrettes (3 12 V, 100 A-hr) are 
still in excellent condition. 

re automotive batteries:

Every reference I have says that automotive batteries should NOT be used
on boats. Two reasons: Standard automotive batteries are not designed to
withstand deep cycling (deep discharge). A few deep discharge/charge
cycles will destroy them. Second, they lack the internal physical
strength to withstand the shock loads encountered in heavy weather
sailing. (My Surrettes have survived three continuous days of close
hauled sailing in 20 to 35 knots winds and seas over 15 feet. You could
feel the boat falling off the waves regularly. After three days the
captain -- me -- decided to heave to. We used one battery for those
three days to power the masthead tricolor navigation light, the knotlog,
and the loran occasionally. As I recall, that battery started the engine
on the first try.) 
 
Alan

    A few deep discharge cycles is on the order of 75, according to
    literature that came with the marine battery I bought last year.

    RE. 7
    
    SORRY SERIES IS WHAT I SHOULD HAVE SAID
    
    SALT WATER WILL CONDUCT ELECTRICITY BUT WILL NOT SHORT OUT THE GEL
    BATTERY.  THESE BATTERIES CAN STAND 1 ATMOSPHER OF DEPTH BEFORE
    FAILING...THE ADVANTAGE HERE IS HAVING A SPARE ANCHOR (ONLY JOKING)
    WHEN YOU ARE IS A POSITION WHERE YOU ARE TAKING ON WATER YOU WILL
    HAVE THAT EXTRA TIME FOR YOUR PUMPS OR RADIO TO CONTINUE WORKING.
    THE DRAIN FROM THE SALT WATER CONDUCTIVITY WILL BE SMALL VS THE
    CHARGE CAPACITY OF THE BATTERY SO THAT YOU WILL HAVE THAT ADDED
    ADVANTAGE.  
    
    I HAVE FOUND THAT REGARDING ANYTHING MARINE ITS EXPENSIVE....I HAVE
    THE 6 VOLT BATTERIES THAT WHOLESALE HERE ON THE WEST COAST FOR $211.75
    EACH, AND ARE RATED AT 1000 CCA (CAN'T GET THE AMPERE-HOUR ANY MORE).
    THESE BATTERIES ARE SUPPOSED TO TAKE 30,000 DISCHARGES.
    
    
    REGARDS TO ALL,
    
    
    JAY  
    
    

    
    5 years...mhmm...  my cheap batteries have now 3.5 years and still fine
                       but the enginemounts broke due to bad weather.
    but there is something else nobody has mentioned yet:
    
    In case you have no separate starter batterie and from time to time
    (lets say once a year) dead electronics (Autohelm,Loran..)you have to
    read on:
    
    When you start your engine with the startermotor,this startermotor is
    working for a short time as generator.(when you stop feeding power but
    he still turns)
    This startermotor is giving a very high voltage of reverse polarity on
    your 12 Volt boardnet.
    All electronics for cars are protected against this reverse voltage.
    But it seems that not all marine electronics are protected.Some of the
    manuals even tell you to connect it to a seperate batterie.(Goldstar
    Radar and SSB radio)
    I had to repair an arly model of Autohelm several times.Symptom: Wheel
    turned only to one side.
    
    There are two possibilities to protect your investment:use a diode in
    serie.This is the best solution.But you are loosing minimum 0.7 Volt.
    The other possibility is to have a diode in parallel.You will have
    no voltage drop but in case of reverse polarity you still feed 0.7 Volt
    of wrong power to your electronics.
    I prefere the diode in serie.Still better would be a separate starter
    batterie.
    
    
    Peter
    
    

re .14:

There is a third, still better solution, to voltage spikes. Connect a 
zener diode (15 to 18 volts say) across the power input to the 
electronics. This will limit the voltage input to the zener breakdown 
voltage. Ample Power (address in a previous reply) sells these diodes.

A very simple solution is to turn off the electronics when starting the 
engine. However, I have never heard of what you describe causing 
electronics failure. As soon as power is removed from the starter motor, 
the motor solenoid isolates the starter motor from the battery. I 
suppose a voltage spike is possible, but the low internal resistance of 
the battery should absorb any destructive spikes. But then theory 
doesn't always work.

By the way, connecting a zener across the output of the alternator will 
keep the alternator diodes from being destroyed should someone 
accidentally turn the battery switch(es) to OFF with the engine running.

    For some systems, you'd need a hell of a zener diode.  My outboard
    drives my battery up to about 16 volts, and it seems to take at
    least 100W or so of load to keep it down to something mildly reasonable
    like 14.7.  I built a local regulator for my LCD depth sounder,
    and have it on my projects list to make a shunt regulator for the
    alternator.
    
    I hadn't thought of the reverse voltage spike from the starter,
    guess that a power schottky diode, anode to ground across the battery
    would be a good idea, 11-20811-01 50V 200A or equivalent would work
    nicely...

    Alain,your are right with the solenoid cutting the power .But that is
    exactly the problem.There is no mechanical switch (except mercury)
    without bouncing.
    
    I have build my own anemometer.With no protection a MC7808 dies in no
    time (real experience) .With a zenerdiode,both go at the same time.
    
    Peter

    At the last Newport boat show I saw a European boat with an AMPERE-HOUR
    meter.  It was a digital LCD readout and probably had a simple micro
    that integrated amps, including remembering where it was when you
    shut of all power.
    
    The idea, which seems like a great one, is that you fully charge
    the batteries (check with a hygrometer) and set the readout to zero.
     For the rest of the season the meter tells you what you put
    in (charging) amps*hrs minus load amps*hrs.
    
    I think the unit was made in UK or Germany.  Anybody know where
    one can be found and approximate price?   
    
    re: transient protection - 
    
    An 18 or 20 volt zener diode is certainly better than no protection,
    but I don't think they have large surge capacities (I'll have to
    look up some specs tho').  The alternatives:
    
    1. eliminate the sources of transients
    2. better protection devices
    3. both 1 & 2.
    
    Eliminating sources:  Every DC motor is an excellent BIG transient
    producer when it is turned off.  I have yet to see a bilge pump,
    fan, water pump etc. have any arc suppression for the poor relay
    or switch or any suppression of the reverse voltage spike created
    when the current is interrupted.  Simple spike suppresion is a 50volt
    1 amp diode paralleled with a 50volt .01 uf (microfarad) capacitor
    mounted right at the motor. Anode (band) goes the the + side of
    the motor.  Higher voltage ratings are fine as well as higher diode
    current ratings, but DON'T use a bigger capacitor.  The diode "catches"
    the back emf spike and the capacitor eliminates most of the radio
    frequency energy that you can hear as clicks on the AM band, and
    which drives your loran crazy etc.
    
    I have seen the alternator transient suppressors for sale, but don't
    know what's inside.  Although not a damaging transient, alternators
    produce RF noise from the semiconductor diodes that change the
    generated AC to DC.  This noise can be a real pain for lorans and
    RDF's.  A simple remedy is a 100 uf 35 volt (higher ok) capacitor
    (polarized electrolytic) from the battery connection terminal to
    negative or alternator frame.  Mount this right on the alternator.
    Electrolytic capacitors aren't great at higher frequencies so parallel
    this one again with a .01 uf. 
    
    protection:  Special devices are made for handling VERY high surge
    curents for brief periods of time.  They are called varistors or
    simply transient voltage suppressors.  One or more of these are
    inside the 110 volt AC outlet boxes you've seen advertised for PC's.
    What they charge you $15 for can be bought at most electronics stores
    for $.79.  Voltage ratings vary, so a 18 volt DC model would be
    a good choice.  It can handle 1000 amp pulses! But, the clamping
    voltage does rise to tens of volts.  Many boat electronics have
    some sort of internal protection and might stand a short pulse of
    30 volts or so.  These things can really make a difference when
    big surges (eg lightning or disconnecting a running alternator)
    hit.  (I should take my own advice as a nearby lightning strike
    wiped out my house fire alarm two weeks ago!).  The safest approach
    would be to install one of these on every sensitive piece of gear,
    as the path big voltages take is not predictable.
                             
    Since suppression and protection are subtly different in the kind
    of transient protection, and since both cost less than $20 in parts
    for an average boat, it's really cheap insurance.
    
    
    
    
    

    A 1N4004's a nice catch diode for bilge pumps, blowers, etc.
    
    MOV's (metal oxide varistors) are cheap transient protectors, but
    they're slow as hell, degrade with time, and it's hard to tell if
    they're still alive.  Semiconductor transient protectors are much
    faster with a corresponding increase in cost.  
    
    General Semiconductor is a major manufacturer of semiconductor
    transient suppressors, and their catalog has a bunch of application
    notes in back for the technically oriented individual.  There's
    one other major manufacturer, but I don't know who.
    
    John

re .18:

>>    At the last Newport boat show I saw a European boat with an AMPERE-HOUR
>>    meter.  It was a digital LCD readout and probably had a simple micro
>>    that integrated amps, including remembering where it was when you
>>    shut of all power.
    
>>    The idea, which seems like a great one, is that you fully charge
>>    the batteries (check with a hygrometer) and set the readout to zero.
>>     For the rest of the season the meter tells you what you put
>>    in (charging) amps*hrs minus load amps*hrs.
    
One BIG problem with this idea: Recharging a battery is not 100% 
efficient. That is, if X ampere-hours are taken from the battery, 
something greater than X must be returned to achieve the same final 
charge. The additional number of ampere-hours required varies with the 
battery, the condition of battery, and the extent of the discharge. But, 
as I recall with doing any research, the recharging ampere-hours is on 
the order of 1.1 to 1.2 times the discharged ampere-hours.

Also, the number of ampere-hours a battery will supply before it should 
be recharged decreases with the age of the battery and the number of 
times it has been cycled. The decline in capacity can exceed 20%. 

Battery voltage gives an excellent measure of how well charged the 
battery is. Much simpler, too.

    re.-1
    
    My Norelco electric razor has a neat four segment LCD display to
    show the battery state at 100%, 80%, 50%, 20%.  I think it works
    off the voltage the NiCad puts out.  That would be a nice indicator
    to adapt to a lead acid 12V system and put on a boat.  I don't want
    to tear my razor apart though.
    
    John

    
.20>  Battery voltage gives an excellent measure of how well charged the 
.20>  battery is. Much simpler, too.

       True about 95% of the time. If a battery is in poor condition (or
    undercharged) it may produce a good voltage reading on a voltmeter
    (which does not load the battery), but the battery may not have
    the "oomph" to provide sufficient current for other things (like
    starting the engine or even running the radio).
    

       Frank
    

re panel meters:

Triplett Corporation makes LED digital panel meters that would be nifty 
for use on a custom electrical panel. Model DT-51A-13 reads to 19.99V 
with an accuracy of 0.1% of the reading +/- 1 digit. Model DT-51A-11
reads to 199.9 mV (same accuracy). This one, with a Simpson 6709 ammeter
shunt could be used to read load current to the nearest 0.1 A (50A max).
These meters are 1.89"x3.78". $58 at Newark Electronics (1988 prices), 
branches all over the country (see the yellow pages). 

re life of conventional lead-acid batteries:

For Surrette series 400 batteries:

% discharge   life in cycles  
             discharge/charge

  100             ~1200          
   50             ~2600       (~7 years at one cycle per day)
   20             ~7000


re alternator protection:

One company sells a diode they call Zap-Stop that has kept the internal 
diodes of an alternator from being damaged or destroyed when the 
alternator was disconnected from a battery while the alternator was 
delivering 100A.

    Re: .13
    
    I have personal experience with what happens when a battery is
    submerged in salt water.  A boat I owned developed a leak which, 
    when combined with pumps which didn't work resulted in the batteries
    going under water.  The effect was impressive:
    
               o Topsides paint was discolored
               o Zincs were immediately and totally wasted
               o The white metal handles of the water tank shut-offs
                 were turned to powder and the soles above these handles
                 were covered with an electolyte residue from where
                 the salt water had boiled.
               o all of the copper wire that became submerged was destroyed
    
    
    So...I have to take exception to the notion that gel batteries are
    better because they will work under water.  The moment that both
    terminals are in contact with salt water a spectacular short followed
    by a very dead battery awaits you.

Here is yet another way to connect batteries. Use a separate battery 
switch for each battery. The common terminal of the switch goes to the 
battery. Switch terminal 1 connects to the engine starter motor. Switch 
terminal 2 connects to the ship's power bus (lights, electronics, etc). 
Use a diode isolator to split the output of the alternator. One output 
goes to the ship's power bus and the other to the starter motor. Be sure 
that the alternator has no_load protection across its output. 

With this arrangement, any battery can supply current to the engine 
starter motor or to the ship's power bus. As long as the 1&2 position on 
the battery switches is never used, the starter motor is completely 
isolated from the electronics, etc. If necessary, all batteries can be 
connected to either the ship's power bus or to the starter motor. Two or 
three almost discharged batteries can start an engine when one can't.

This may not be quite as simple as the standard system, but it does have 
some advantages. Just a thought.

Alan

    I agree with a previous note: Just because the battery voltage indicator
    is indicating a "good" voltage (which should be 13.7v, right? erm.
    I'll be glad to see the day when any battery registers that figure.
    I've seen anything from under 12v to 16.5v).
    
    It's the battery voltage UNDER LOAD like turning the starter that
    really counts. And that can vary rapidly from one minute (second?)
    to the next, also.
    
    Basically, I could never figure out when a battery is good or bad,
    except that if it gives me trouble two or three times after it has
    been under a charging current for a few hours, then you know.
    
    If anyone knows a straight-forward, step-by-step practical and
    quantitative way of determining battery condition, I'd be glad to
    hear it......
    
    Tally-ho,
    
    Ray

re .26:

One way: Fully charge the battery (whatever fully means for your
charging system). Let the battery sit for 24 hours with no load. Measure
the battery voltage. Now place a load on the battery -- say 10 amperes.
Measure the battery voltage every hour or so. Keep the load on the
battery until the battery voltage drops to, say, 11.5 volts. This will
give you a good idea of the condition of your battery, especially if you
do this procedure once a year or so. The amp-hr capacity of the battery
is roughly the load current times the number of hours until the voltage
drops to whatever minimum you choose. If the battery has a damaged cell,
the battery voltage will fall very quickly under even a small load, like
in a couple of hours. This test should reveal, especially when comparing 
two or more similar batteries, any battery damaged by age and/or abuse.

    Saab 96 manuals had a good dead cell test, which was accomplished by
    measuring battery voltage while cranking engine with starter.  The most
    common failure is a dead cell, and their test would identify that
    clearly.  Anybody nursing along a 96?
    						J

    RE: .28  "Anybody nursing along a 96?"
    
    Yes, why?  You mean the car right?  I'll have to look in the SAAB
    Bible and see if I can find the procedure you mention.
    
    

[moved by moderator -- see also Note 1102 and possibly others]

================================================================================
           <<< MSCSSE::SYS$SYSDEVICE:[NOTES$LIBRARY]SAILING.NOTE;1 >>>
                                  -< Sailing >-
================================================================================
Note 1366.7                Manuals for older engines?                     7 of 7
ROLL::NELSEN                                         62 lines  27-OCT-1989 11:58
                 -< Advantages to dual bus pwr distribution? >-
--------------------------------------------------------------------------------
Your suggestion of using separate House and Engine buses is intriguing, but 
leads me to have questions concerning its advantages.  In my analysis
below, it would seem that the only advantage of having a separate house bus is 
that house equipment (Loran, things with memory, etc) can be isolated from the
voltage sag that occurs when the engine is started.  Are there any others?

We're considering a redesign of the distribution system for a boat that is 
going to have a heavy load of equipment for ocean racing.  Reliability and 
simplicity are both  of utmost importance as this boat will probably be 
in single handed races as well.

Compare it with this simpler system:

- single bus for engine and house
- two batteries (maybe three) connected with separate heavy SPST switches 
  to that bus.
- distribution/fuse box selected to be large enough so that no short cuts are
  taken to bypass it when other equipment is added.
- the main distribution box will have accurate volt meter installed in it, 
  possibly a current meter to measure charging rate. 

The SPST switches permit full flexibility of connecting or disconnecting the
batteries.  

In use:

There would always be one good battery reserved for the 
engine. It would be disconnected from everything and held in reserve. 

When charging, both batteries would usually be charged in parallel, and when 
engine is off, one battery would be disconnected.  Although, either battery
could be charged separately.

Because of the heavy duty single pole switches, there is no problem with 
starting engine with one battery, and then switching the second battery 
(which may be low) into the circuit. 

If one battery has a shorted cell, the volt meter will detect this. As each 
battery can be checked individually with and without load (using the distn box).

Re engine interference:  There would be no problem with electrical interference 
while the engine is running, as we have been able to eliminate all such 
interference in the past.  Aha, I see one advantage of a separate house bus: 
eliminating the house bus from the voltage sag that occurs when the engine 
is started.

Perhaps, we would have to make sure that the voltage sag during the  
starting motor surge  doesn't dump the settings in the Loran and in the 
automatic helm (we have had a problem with this one!).   This could be the only 
problem with not having a separate house bus -- namely, isolating the house 
service during the engine start voltage dip.  One fix might be to make sure
that heavy enough wire is used to the starting motor and that battery 
connections have sufficiently low resistance.


Other than isolating the house system from the voltage sag when the engine is
started, I don't see any advantage offered by having a separate Engine bus 
which contains the alternator.  This alone might be sufficient reason to go
with the separate bus... but am I missing something else?


Don

re .30:

See note 926.25 for another (better, I think) idea. 

There is a simple solution to loran crashes caused by voltage drop from
starting the engine. Connect the loran to the ship's power bus through a small
diode. Also connect a small lead-acid battery (such as a motorcycle battery)
directly to the loran. This small battery is normally kept charged by the
ship's power system. When the voltage on the ship's bus drops below the
voltage of the small battery (ignoring the diode voltage drop), the small
battery keeps the loran power input at 12 v. 

I've installed this system on our boat. Our loran stays up even when the 
voltage on the ship's bus is so low that the starter moter will barely crank 
the engine. The battery is mounted behind the circuit breaker panel. This 
system has one additional advantage. If for some reason the main batteries 
fail completely, the small battery has enough capacity to power a VHF radio, 
loran, satnav, etc, for a brief time. 

[Moved by moderator. Yes indeedy, sports fans, let's keep discussions in 
logical places. Discussing power systems in a note about old engine manuals 
doesn't strike me as all that logical. This note seems more appropriate.]

================================================================================
           <<< MSCSSE::SYS$SYSDEVICE:[NOTES$LIBRARY]SAILING.NOTE;1 >>>
                                  -< Sailing >-
================================================================================
Note 1366.7                Manuals for older engines?                     7 of 7
ISLNDS::BAHLIN                                       29 lines  27-OCT-1989 12:55
                   -< Should this be in the battery topic? >-
--------------------------------------------------------------------------------
    Actually the system you've proposed isn't all that much different
    than mine.  In both there is the opportunity to maximize your choices
    of battery connections.   My main reason for doing the switches
    was to eliminate the need for isolators which generate heat, create
    loss and can fail.   I don't believe that isolators are optimal
    for combining batteries.
    
    My reasoning for the dual buses was:
    
    	1) Eliminate the need for filters in the distribution system.
    	   They create losses, heat, and can fail (just like isolators).
    	   When you go to a high output alternator you need to go to
    	   appropriate sized filters that are expensive.  My alternator
    	   noise is constrained to the world of the engine, where it is 
    	   harmless, by the switching.
    
    	2) Allow the batteries to discharge to 50% before being recharged.
    	   When you have everything on one bus and do day tripping (as
    	   I do) it is possible that your batteries don't get any
           'exercise'	this is as harmful as too deep a discharge.
    	   I wanted a way to LET them go down an appropriate amount
    	   before being recharged.
    		
    I never even thought of the sag issue you raised but it is certainly
    valid and maybe another unwanted part of the starting glitches is
    what must certainly be huge spiking coming from the starter motor
    itself once you release the key.  Wouldn't this dc motor become
    a dc generator for a short period after release?
    

re .25:

The battery isolator can be eliminated if the alternator is connected to the 
ship's power bus and at least one battery is always connected to that bus. 
I've never had any problem with alternator electrical noise, but good filters 
aren't all that expensive.