Rechargeable AA cells are very popular for a large variety of portable applications. The number of brands is also high, and the cell quality can differ considerably. Cell capacity is sometimes different from that specified, and the capacity often deteriorates dramatically after a limited number of discharge cycles. ….
See Maxim Application Note – Simple Characterization Circuit for Rechargeable AA Cells
This characterization circuit, plus a PC and some software, accurately measures the full discharge cycle for a rechargeable AA cell. Cell capacity and output resistance can easily be determined from the curve resulting from these measurements.
In Figure 1, the simple circuit is connected to the USB port of a PC. No external power source is required because power is extracted from the USB bus voltage. U1 (DS9490R) is a USB dongle that converts the USB protocol to the 1-Wire® protocol, thereby allowing the PC to communicate with the key circuit component (U2).