Rechargeable Battery Tester

I am accumulating a fairly large stack of rechargeable batteries from battery packs where one or more cells have died. They include LiIon, NIMH, but mostly NiCad. Until know I have been putting in all new cells when I rebuild a pack. I was thinking that I would like to break the packs apart and test each cell to determine its capacity. Then knowing that, rebuild the packs with similar capacity cells.

I have some general ideas on what I would do for a circuit. Something along the lines of a fixed load (high wattage resistor) connected to a high impedence input voltage comparator, that allows a timer to run until the threshold is breached (test battery voltage drops below x Volts).

Should I run the timer based on current or voltage output? What threshold for current or voltage would you recommend? What load would you place on a single cell to perform the test? Or is there a better methodology?

I have one of these; works great

That looks very nice! Quite a clever idea.

Looks cool until I see the price. Perhaps a little overkill for testing a single cell.