I've never written a customer review in my life, but I don't want anyone else to make the same mistake I did by buying this product. When I received the charger, it appeared it had already been used. I hooked it up to 3 different batteries, it showed all 3 were 100% charged, which is highly unlikely. I hooked it up to my car, it showed 57% charge, I unhooked it and now my car won't start. I've checked the car for loose connections, relays, fuses, boosted the battery etc. and nothing. This charger somehow damaged my car's electrical system or battery, now I have to get the car towed to the repair shop. I wouldn't have complained if it just didn't work, but now I'm going to have a towing and repair bill and I've lost the use of my car for a couple days. Showed 100% charge on uninstalled batteries and damaged my car when hooked up to an installed battery. I've worked on cars and followed the instructions for the charger.