I had many failures with my SE-1-12S. Used it to charge the car when not in use for a long time. In order to bring the car to the inspection station, the air conditioner had to be disconnected from the unit. However, when I got to the inspection station and the guards there turned the car off and started it again, the battery was dead. Something similar has happened to me many times. I thought it was an electrical problem with the car, but after changing the battery, the same problem appeared. I removed the SE-1-12S (I used a regular maintenance charger instead) and this problem went away. After this experience, I will not buy any more devices from Schumacher.