Vaughn wrote:
"COLIN LAMB" wrote in message
ink.net...

In fact, you can often hang a auto lamp across the battery with a digital
voltmeter and watch the voltage drop. The less drop, the better the battery.


That is exactly how I have been doing it for years, and I have never found
a need for anything more fancy. For small gel cells, (as are used in gliders) I
use a digital voltmeter and a 50-watt sealed beam light. For larger batteries,
I use a commercial load tester that you can buy at NAPA or any similar auto
parts store for about $50.00 US.

It sounds like you are effectively doing an internal resistance
measurement. Do you have chart of volt drop, load, and good/ok/bad
decision for various size batteries? I've not seen that sort of thing in
battery data sheets, so I assume you have to develop the numbers
empirically.


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Eric Greenwell
Washington State
USA