This device is the best solution for cars and trucks that are draining their batteries for unknown reasons. My truck and many others that I found out I had problems like this trying to fix. The solution could be one of the many things I didn't have time to research as winter approached. This easy to install device monitors the battery, when the voltage reaches a certain point it shuts down the battery, reduces its discharge and leaves the battery ready to start the car. To reconnect, just press the brake pedal, wait a few seconds and start the car. A buddy of mine who works as a mechanic in the city saw it on my truck and said all city ambulances have one like this to be on call all the time. Since mine has been switched off many times over the winter, I know it's doing well. Could always start.