BrianH has posted a useful Instructables project that tests the capacity of rechargeable NiMh and NiCd batteries. The circuit is based on an Atmega168, and functions by draining the AA batteries (from 1 to 3 batteries) then computes and reports the capacity in mAh. It uses a Nokia 5510 graphic LCD to report battery condition and three MOSFETs used to switch the resistive load on and off during testing.
Versions of the project using the Arduino board or a standalone Atmega168 or 328 are provided with schematics and commented source code.
Via Hack a Day.