Re: Self healing battery? follow up

["Joe Smalley" <joes@worldfront.com>]

The biggest load I have is only 600 amps at 12 volts. Maybe I can get
another one put together for the test.

I have two concords in this condition. I will try to do the same and see if
they heal too.

Joe Smalley
Rural Kitsap County WA
Fiesta 48 volts
NEDRA 48 volt street conversion record holder
joes@worldfront.com


-----Original Message-----
From: Lee Hart <leeahart@earthlink.net>
To: ev@listproc.sjsu.edu <ev@listproc.sjsu.edu>
Date: Saturday, October 30, 1999 4:52 AM
Subject: Re: Self healing battery? follow up


>Joe Smalley wrote:
>> The Dynasty 12-475 measure as follows (clip...)
>> These are the batteries I want to drag race with next season. Which
>> four would be the best choice to put in the car?
>
>First, I assume that amp-hrs are not your limit during drag racing with
>these batteries. Even at 1000 amps, you aren't taking much out of a 100
>amp-hr battery in 15 seconds.
>
>So, what really matters is internal resistance, i.e. voltage under load
>after X seconds. Can you rig up a load that pulls 1000 amps? Pick the 4
>batteries that have the highest voltage after 15 seconds at 1000 amps.
>
>A follow-up on my self-healing Concorde:
>
>I called the factory and talked to an applications engineer (Skip ...).
>I started to explain what happened, and before I finished, he said,
>"Wait, let me guess. After 5-7 days charging at 15v, it healed; the full
>amp-hrs came back."
>
>He has worked to for several battery companies, and with all types of
>lead-acid batteries. For most types, the rule is that there is no point
>in charging more than 72 hours; if it hasn't recovered by then, it never
>will.
>
>However, AGMs are different. It is possible to get one or more cells in
>a battery so far out of balance that normal charging will not equalize
>it. The voltage on the good cells gets so high that the charging current
>falls very low; so low that you never bring the lower cells up to full
>charge.
>
>His theory is that batteries that have sat for a long time might have
>cells that self-discharge at different rates, causing this large
>imbalance. The v-e-r-y  l-o-n-g  s-l-o-w charge at high voltage
>eventually does the trick. He said it literally takes 5-7 days with the
>Concordes.
>
>The bad news is that the rest of the cells that are fully charged are
>using water, and the battery is gassing. Unlike Optima and Hawker AGMs,
>the Concordes have a very low pressure relief valve; only about 1/2 psi.
>Thus very low overcharge rates can cause venting. That's why they have
>very conservative charging recommendations.
>
>The good news is that Concordes have removable vents, and you can add
>water to them. You have to break the tape seal and remove the cover
>(voids the warranty). The vent plugs are glued in place, but pop right
>out with a twist. You can top off the water, and replace the plug.
>Replacing the glue isn't necessary; the plug is a press fit.
>
>I have put the zombie battery back in my EV, and will see what develops.
>I am also going to try the 5-7 day treatment on the second lowest amp-hr
>battery in the pack to see what happens. Since I can add water, I'm not
>so afraid of venting them any more.
>--
>Lee A. Hart                     Ring the bells that you can ring
>4209 France Ave. N.             Forget the perfect offering
>Robbinsdale, MN 55422 USA       There is a crack in everything
>phone (612) 533-3226            That's how the light gets in
>leeahart@earthlink.net                  Leonard Cohen
>
>