We have an old VW Bug with some mysterious power drain. Sitting in the driveway undriven for more than about 3 days and it would need a jump to start. If you have ever had to access a Bug battery you know what a chore this can be! So we bought this charger and keep it on the dash and plugged into the lighter socket when the car is not being driven. We have gone a week and more and never had to have another jumped battery again! This thing is great for cars that sit out in the sunshine and need a little boost for their battery.