Searon Universal Digital LED Battery Indicator Tester Gauge Status Charge Monitor Meter Gauge 12V 24V 36V 48V 72V Diagnostic Tool LED Battery Indicator works on 12V 24V 36V 48V and 72V Lead-acid batteries. Displayed using a 10 segment LED bar graph display from full to empty Specifically designed to monitor the power level of battery while charging or discharging The second LED from the left flashes as a warning that the batteries voltage has been discharged to 80% of their capacity. At a 90% battery discharge, the red and yellow LEDs will alternately flash to indicate a very low voltage capacity is remining.