Re: (ET) Lessons learned: batteries and diodes

["David Roden (Akron OH USA)" <roden ald net>]

On 29 Oct 2001, at 10:44, Jeremy Gagliardi com wrote:

> The small, 12V, car or boat battery chargers are not really sufficient 
> for
> these large, deep-cycle batteries. 

It sounds like your 12-volt chargers were cutting off too early, before 
the voltage reached 2.4 to 2.45 volts per cell.  If true, that's not 
adequate for any lead battery, deep cycle or otherwise.  The dealer 
should give you a refund on them.

It's true that low-current chargers (6 amps or so) will take a good while 
to charge up a 220 amp hour battery (appreciably more than 36 hours from 
100% DOD because the charge tapers).  But that's not much of a problem 
for a machine that's seldom used more than once a week.  

Your experience notwithstanding, I stick by my recommendation.  A set of 
three 12-volt chargers (or six 6-volt) will charge more effectively and 
make your pack last longer, as long as they have a reasonably good charge 
algorithm.

My 10-amp Exide chargers have a so-so algorithm; they are basically taper 
chargers with a "cycle-dropping" controller, that is the type that cycles 
the charger on and off at intervals of a second or so to control finish 
voltage.  They push my gel cells up to 14.3 volts (on-charge voltage), 
which is about what the battery manufacturer recommends.  They've worked 
just fine for me for about 2 years now.  I wouldn't hesitate to use them 
with flooded golf car batteries, though I might turn the voltage limit up 
a bit.

The GE charger's control is fairly crude, and it appears to me that it 
mostly overcharges.  Some people think that overcharging is better than 
undercharging.  They're both bad for batteries.  

But again, the ET is typically run once a week at most, so even if cycle 
life is dropped from the ideal of 700 or so cycles (for golf car 
batteries under optimum conditions) to 300 or 350 cycles, you still get 6-
7 years of life from the pack.


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1970 GE Elec-trak E15 36vdc
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