I purchased 2 of these devices for my trucks that don't get used too much and wanted to keep the batteries from sulfating too much. I have been using them for about 6 months now, and they keep my batteries at the correct charge levels. I have them permanently installed with a heavy duty outdoor grade extension cord out of my grill so when I bring the trucks back to my shop, I just get another extension cord and plug it in to the wall socket. Since I am a HAM radio operator, I have rigs in my truck, it is perfect for those days when I am tuning the antennas, or programming the radios. Don't have to worry about my battery going dead either.