... 2, when red light is lit, charging is complete. 3,12 V Digital Battery Tester 1, LED display ... indicates condition 2, Charger check: when red light is lit, charging ... accelerate your engine to 2000 rpm when the red light is lit ,charging circuit is ok.4, Battery ... check : red light must remain lit when starter motor operates.6, 12 V Digital Battery Tester 12V LED ...