Yep, on a 12v battery, would mean max of 8 or so Amps (P=I*E). Just means a longer cycle time, but should still be able to test capacity, etc. Bob Nuckolls is the one that advocates this device for testing batteries. Somewhere on his website, he also tested a bunch of battery management devices.
Other thought is to use it along with your corn cob resistor :)
Alan
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Alan,
Actually, if you lower the current during the test you will get a higher capacity reading. Various internal losses increase as a squared function of the current: I^2R. During really high power discharges the losses are enormous and you can loose most of your capacity as heat. You can end up with very little energy actually making out the terminals. This is why the Ah rating has to pegged to a fixed discharge current to get a 'nominal' capacity value. 25A or 1C for a 25Ah rated battery. Ideally the resistance value would be varied during the test to keep the current constant. In my case, the external resistance is constant and so the current varies a little during the test. I'm not sure how the official Concorde battery tester works, resistive element or current regulated. We have both types here at work for testing huge high voltage/high power battery packs.
I saw an article by Bob Nuckolls http://www.aeroelectric.com/articles/battest.pdf about a homemade battery tester and was surprised that none of the above effects were mentioned. Then again, he wasn't actually trying to measure the capacity quantitatively, but only determine a relative comparison. still stuck with my corn cob,
Chris
Chris Zavatson
N91CZ
360std
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