PRO12-48R Battery Indicator For 12 Volt Systems The ONLY rectangular 12 volt battery indicator that works on all wet lead acid batteries. Works on standard lead acid batteries and newer generation batteries made by Exide, Trojan, Interstate, Walmart, PowerTron, AGM (Glass mat) and other brands. Standard Lead Acid Batteries that have a state of charge range from 10.38 to 12.34 volts. New generation batteries with a state of charge range from 11.56 to 12.72 volts. Normally closed relay output operation for controlling secondary devices, 5 volt logic- limited to 200 ma.