This Nicad battery tester discharges the test battery at a rate of 500 mA. When the endpoint of 1 V (determined by set
ting of R3) is resolved, pin 2 of U2 becomes low, deactivating Ql and disconnecting the test battery from the circuit. Power for U3 comes from the 12-V regulator in series with the battery being tested. A clock or timer can be plugged into SI to indicate the time it takes to discharge the battery under test.