Poor Man's Capacity Measurement
Well, if you have a good DVM, some electronics experience, and LOTS of free time, then you can make a poor man's discharge acquisition system. It can give approx mAH values:
(1) Take a wild guess at the cell's capacity. Don't worry about being wrong, but attempt to nail it as close as possible.
(2) Charge the cell at a C/10 rate (per your guess) for 14-16 hours. Second best is to use a quick charger set to single cell mode.
(3) Divide the guessed capacity by 5 (C/5). This will be your discharge rate. For example, a 600mAH cell will be discharged at 120mA.
(4) Choose a resistive load that provides the C/5 current draw. A 3V flashlight bulb makes a good load. It does not have to be exactly C/5. But you must record the load current for later use.
(5) Continue discharging until your cell measures exactly 1.0VDC. The voltage monitoring will require you to check every 5-10 minutes. When the voltage is met, then record the number of hours it took. Re-measure the current draw at the lower voltage.
(6) Calculate the average load current: mA = (Current1 + Current2) / 2.
(7) Calculate mAH: mAH = mA X Hours.
After doing this once or twice I expect that you will decide that those unmarked cells are best used in the kids' toys.
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