washer@sequent.com (Jim Washer) (06/20/91)
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
edh@sqa.dsg.ti.com (ed humphries (ASOC)) (06/20/91)
In article <1991Jun19.181233.12893@sequent.com> washer@sequent.com (Jim Washer) writes: >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. >Comments? Flames? Circuits? > - jim KG7HH 1-503-578-3171 CQ magazine had a very nice article with a circuit a few months ago. This months issue had the circuit (labeling) correction I've been expecting. I am planning on a modification to incorporate a meter (I like visual indi- cators myself). Also, I'd like mine to be adjustable (for 9v packs as well as 7.2v). If there is enough interest, I'll post the (ascii version) circuit. But not till after Field Day! :-) -- Ed Humphries Texas Instruments, Inc. 512-250-6894 N5RCK Internet ed.humphries@hub.dsg.ti.com