Re: (ET) Hoping To join Your Group

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

On 18 Oct 2002 at 9:10, SSemicon aol com wrote:

> hey have
> been in service for 3 years now, & despite the heavy use I give them, I 
> have
> yet to ever have to water them. This Is due to the fact that because I 
> use
> very little current through any battery taps, consequently I never have 
> had
> the need to equalize the battery bank.

Welcome to the list!  I look forward to hearing more about your machines.  
I 
don't quite know what you mean by "I would like to join your group, but 
for 
some reason have not been able to do so through the traditional methods."  
I'm pretty sure that if you can send mail to us, you can receive it.  If 
you 
receive only one copy of this email, write me back and I'll try to help 
you 
"get connected."

I beg to differ with you to some extent on batteries.  Granted, there's a 
certain amount of "religion" where batteries are concerned.  What follows 
is 
my "sermon," which is based on quite a few years of using lead batteries 
in 
road EVs -- a significantly more strenuous application than Electraks.  

Equalization is essential for any battery, even a single battery.  Not 
tapping the pack is a good thing, but it doesn't prevent unbalanced cells. 
 
Manufacturing tolerances are far from perfect, and cells differ even in a 
single battery, so with use they will always get out of balance.  The more 
batteries (and cells), the more this happens.  

Flooded batteries that are discharged equally usually don't need to be 
equalized on each cycle, but they should be equalized about every 5-25 
cycles (determine this experimentally -- depends on use, manufacturing 
tolerance, and age).

Gassing and water usage are normal when charging a lead battery.  The 
absorption phase of charging will gas a battery because the voltage 
required 
to attain a full charge exceeds the gassing threshold.  At this voltage, 
the 
water breaks down into hydrogen and oxygen.  

Flooded batteries should be finish-charged at a regulated voltage of 2.4 
to 
2.45 volts per cell, until the current falls to 1/20 to 1/40 of the 20h 
amp-
hour capacity expressed in amperes.  During this phase, the cells will be 
gassing freely.  Many VRR (valve regulated recombinant) batteries will 
require a lower finish current to prevent venting and consequent loss of 
water, but they still must gas.

If equalization is required, the current should be held at this level for 
several hours or until the voltage stops rising.

If you have not needed to water your batteries in 3 years, you are almost 
certainly undercharging them.  They will eventually degrade from 
sulfation.  
But at least they aren't likely to fail from overcharging!


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1970 GE Elec-trak E15 36vdc
1974 Avco New Idea 36vdc
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