I have a 2003 GMC Envoy that drains the battery every 3 weeks. I put this on the battery and it showed the battery was waiting for a low charge and after a few days started charging, it showed the battery was full. I just left it plugged in because it won't charge with a fully charged battery, but when it's empty again it starts charging again. It worked for five charges, after which the power contacts began to crackle and the LED indicators blinked and went out. So I bought the one with the power cord.