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From: washer@sequent.com (Jim Washer)
Newsgroups: sci.electronics,rec.radio.amateur.misc
Subject: Nicad battery "tester"(?) wanted
Message-ID: <1991Jun19.181233.12893@sequent.com>
Date: 19 Jun 91 18:12:33 GMT
Sender: washer@sequent.com (Jim Washer)
Organization: Sequent Computer Systems, Inc.
Lines: 21

With all the discussion about nicads, nicad capacities, nicad memory,
nicad charging techniques, nicad ......, I thought it might be nice to build
a device that would give me some quantitative measure of a batteries
capacity.

I thought that building a circuit that would draw some fixed current,
until the battery voltage dropped to some pre-selected value would suffice.
An lm317 would work well to set up the constant current, with a little thought
I (might)could develop the auto shutoff to avoid over-draining the battery and
the timer circuit to record how long it held the voltage up.

Does this sound like a reasonable idea? My plan is to 'test' new
batteries when I purchase them, and then periodically test to see that they
have not gone sour.

Is drawing a constant current a reasonable test for a nicad? How much current?

Comments? Flames? Circuits?

tia
 - jim KG7HH 1-503-578-3171