Re: from the Hawker nursing home

[Lee Hart <leeahart@earthlink.net>]

Gary Graunke wrote:
> Continuing the saga of newbie meets aging battery pack of 42AH
> Hawkers...
> There is probably experimental error here, since I tested them (using a
> NiChrome tester for about 10 seconds

Nichrome has a nearly zero temperature coefficient, so the resistor
should not have changed value as a result of heating. However, some
cheap testers may not bother with nichrome, and just use a cheap pieces
of steel wire --  which *does* change its resistance substantially with
temperature.

> The load test results... [snip]

Good. Now you have battery voltage and internal resistance for at least
one state of charge.

You didn't mention what load current the tester draws. If you know it, a
Hawker battery data sheet will tell you what kind of voltage drop you
should expect for these batteries. For example, 12.8v no-load, 11.6v at
100 amps; internal resistance R = (12.8v-11.6v)/100a = 0.012 ohms.

I've been testing some Hawker SBS60 48ah batteries; a 25amp load will
pull them down about 0.2-0.3v in 10 seconds. Since some of yours drop
1v, and some drop 2v under load, you are obviously drawing much more
current, and there are obviously going to be some more weak batteries.
-- 
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