tested on three different batteries, motorcycle battery 12v I plug-odd minutes gets the green light on full charged. the second battery has discharged 50 amps auto 1/3. out of 12 volts. I put on slow charge and 2 hours battery out of 13.6 volts. 3rd test on a car battery 120 amp. in qq minutes, diagnostic 13.5 volts. really excellent this charger! i hope that it will take me several years. attractive price and good quality set. to buy eyes closed !!!