Alternator Tester & Car Battery Tester 12V Test Battery Condition & Alternator Charging (6 LED indication) Alternator Tester & Car Battery Tester 12V Test Battery Condition & Alternator Charging (6 LED indication) Alternator state check, battery state check, check before charge and overload display Alternator check : accelerate your engine to 2000 rpm when the green light is lit ,charging circuit is ok Battery check: indicate the percentage charging in the battery Charger check: when green light is lit, charging is complete