low-tech: dead Optima

[Dan Thompson]

Kurt wrote:
> I drove my car maybe once/month. When I did drive it, it was running
> for 30-45 minutes each way, plenty to charge the battery.
<snip>
> Since September (when my daughter started school) I've been driving my
> car about every other week or so.
<snip>
> So I pulled the battery and put it on my charger for a few hours, but
> the charger is either broken or too wimpy for the studly Optima,
> because the battery had no more juice after charging than it did
> before.

Sounds like the conditions were ideal for the death of the battery.
Lead acid batteries have an internal discharge rate of about 1% per day.
Couple that with the parasitic losses of the car's electrical system
(alarm, clock, etc.), low as they may be, and your battery could have
been discharging upwards to 50% when you drove it once a month.

As a battery is discharging, the chemical reaction causes soft lead
sulfate deposits form on the positive and negative plates inside.  If
left in a discharged state, these deposits harden and crystallize and
cannot be dissolved when the battery is recharged.  The net effect is
that the battery's capacity is reduced.  If enough of this "lead
sulfate" builds up on the battery plates, the battery will no longer be
able to accept or maintain a charge.

It sounds like this is what may have happened to your battery, Kurt.

FWIW, I have a yellow top Optima that sat in a car for over a year, and
when I finally got to it, it wouldn't accept any kind of charge.  Just
for grins I gave it to my friend, who has a renewable energy (RE) setup.
One of the things he has to help maintain the health of his battery bank
is a "battery desulfator", which basically a uses the batteries' current
to pulse the bank to dissolve lead sulfate crystals.  When he first
checked the battery, its voltage was about 5.5 volts... a dead short to
a charger, for all intents and purposes... it would accept no kind of
charge.  He put this desulfator across the terminals for a day or so
and, with no kind of charging whatsoever, the battery voltage came back
up to around 10.5 volts.  He then began to cycle the battery, charging
and discharging it and keeping the desulfator on it the entire time.
It's been about 3 months now and we figure the battery is up to around
95% of its original capacity.

Here's a great resource on lead acid batteries:
http://uuhome.de/william.darden/index.htm

Good luck!

-Dan