usable life cycle 1

[wario]

I would like to design a circuit that will determine the number of usable life cycles of different AA batteries by charging them and discharging them and counting the no. of charge/discharge cycles.Any ideas?

 

[Skogsgurra]

One idea is that it will take a lot of time to do that. I think that it is important that you let the battery "rest" between the cycles if you want to get reliable results. Also, be sure that the ambient temperature corresponds to where the batteries will be used. Lab temperature usually makes batteries look good while actual use in a cold climate makes them look very bad.

You need to automate the test rig. I would think of using one of these small PLCs that cost next to nothing (abt USD 200). The Siemens LOGO! can easily be set up to do the cycling and the counting. You will need a couple of voltage comparators to detect charge/discharge end voltages (use an opamp on a piece of perf-board and supply via a resistor and zener from the 24V DC that feeds the LOGO!).

You can save much time by running multiple tests from one PLC. They have plenty of timers and counters and by having the discharge resistor permanently connected you can test four batteries simultanously from one LOGO! You will waste some energy, but I wouldn't mind in a test situation like this.