US Patent 9110107 Battery test circuit with energy recovery

A battery test circuit for testing batteries in a working circuit having a plurality of batteries includes a DC step up converter. The DC step up converter may be selectively interconnected between a first one of a plurality of batteries and a second one of a plurality of batteries, to draw a test current from the first battery and to supply current at an elevated voltage to the second battery. The test circuit further includes an indicator output for providing a signal indicative of whether the first battery provides the test current substantially at its rated voltage.