Re: (ET) batteries

["David Roden" <etpost drmm net>]

A specific gravity of 1.25 is equivalent to about 80% charged.  Here is a 
chart which references SOC with SG and open-circuit voltage :

http://evdl.org/pages/socvolts.html

That 1.25 may be as much as you can get if your batteries are sulfated 
from 
chronic undercharging.  (There are other mechanisms that can destroy 
capacity.  Overcharging is at least as bad; it causes positive grid 
corrosion.)

Gassing is not an indication of overcharge, it's a normal consequence of a 
normal charge.  Batteries always gas when they exceed 80% SOC (2.4 volts 
per 
cell measured while on charge).  If yours haven't been gassing freely at 
the 
end of each charge up to now, you probably >have< been undercharging them. 
 
You can try a long, slow equalizing charge, but most likely you won't get 
much improvement.  Sulfation is irreversible.  The capacity is lost 
forever 
because the active material is lost forever.

Although "exercising" (cycling!) batteries can improve their capacity if 
they haven't been used for a while, there's no need to discharge batteries 
to any particular level, such as 20% SOC.  That's a myth.  In fact you'll 
get the most economical service when you size them so that the average 
day's 
use discharges them to 50% SOC, but again that's not a hard and fast, drop 
dead rule.

Just use them.  Be happy.  Stop using them when the voltage under load 
falls 
to 5.75 volts per 6v module, or when you're done working. Then, charge 
them 
without delay, using a good charger that shuts off when it's done.

I haven't used Harry Landis's controller, but from the description he has 
posted, I would call it a battery maintainer and not a charger.  I don't 
have any need for a maintainer.  In fact I think most maintainters do more 
harm than good when left connected all the time.  IMO, it's better to 
store 
unused batteries in a cool, dry place and charge them every 2-3 months, 
than 
to leave a charger of any kind connected to them continously.

Mr Landis's charge algorithm is certainly interesting, but it doesn't 
match 
the algorithm suggested by any battery manufacturer I know of - not for 
cyclic use, and not for float use.  Nevertheless, some people report that 
they've used it successfully for cyclic charging.  Apparently you're not 
among them.  Sorry.


David Roden - Akron, Ohio, USA

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