We own a fleet of trucks that carry vehicles across the country, we often have vehicles do not start after being on the trailer for 1 week. Open up the box, so excited to take it out on a long trip. Charge it up the night before, next morning still not charging. Brought to my friends who has the same jumper, his charger does not charge it either. So disappointed! Now we have to wait another week to see if we can do an exchange. We were hoping to buy 7 of these, one for each truck. We will give you guys one more chance.