Works as advertised, but if you leave it plugged in over the winter and your house or outlet loses power, note that it won't start charging automatically. Someone has to turn it off, turn on your car, and then connect the service device to start the charging and service function. I don't know how to solve this problem for 3-4 months of absence. I'm considering a UPS, an uninterruptible power supply, to keep charging mode up. Very disappointed when charge/maintenance mode fails to restart after power failure.