Re: More about Battery Life, pls.

[Lee Hart <leeahart@earthlink.net>]

Bob Bath wrote:
> I noticed the part about overcharging.  Now, if I
> follow the e-meter, I'd be equalizing ever time;

Then your E-meter's charging parameters aren't quite set up right. You
can set the charged voltage and charged current (percent) so it resets
well before the end of charge occurs if you like.

> Second, I hear that it's good to "drive every day,
> charge every night."  But if I didn't pull more than a
> kWh or two, not good to recharge. Is this correct?

It's a tradeoff. If you only drive short distances, not charging every
time reduces damage from overcharging, but increases damage from
sulfation.

If you didn't discharge too deeply, and know you are going to use the
car again soon (within a day or less), you might as well not recharge. A
good example is if you use 25% of the charge driving to work, it sits 8
hours, and then you use another 25% driving home. In this case, NOT
charging at work will extend battery life. You aren't exceeding 50% DOD,
you have cut the number of charge cycles in half, and sulfation doesn't
matter over such a short time.

But the longer it sits, and the deeper the discharge, the more of a
worry sulfation becomes. For example, suppose your EV is a second car.
You drive to church and back every sunday, using 25% of your charge. It
would not be good to let it sit at 75% SOC for a week, drive it again to
church next week, then recharge it; sulfation would reduce battery life.
-- 
Lee A. Hart                Ring the bells that still can ring
814 8th Ave. N.            Forget your perfect offering
Sartell, MN 56377 USA      There is a crack in everything
leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen