The project allows you to analyze characteristics of unknown/junk battery especially the capacity and variation of the voltage on discharge. It is controlled with a PC via a serial port. No external power supply is required because it is powered by RS-232C signals. It uses ATmega48 as main controller for dummy load and constant current circuit.
For measurement of battery voltage, four-wire method is used to eliminate an error due to drop out voltage at the wires and contacts.
This is needed at high current and low voltage cells, such as Ni-Cd and Ni-MH. I am using JST EHR-2 wire to PCB connector for my projects so that a two contact connector B2B-EH is also added on the board.
Read more: Simple Automatic Battery Discharge Analyzer using ATmega48 microcontroller