Got off the plane at midnight last night to find my vehicle dead. I plugged my fully charged Mighty Jump into the cigarette lighter and waited 15 minutes. I am very disappointed to write that this gadget is simply a failure. The claim on the shopping channel insisted that this product would be good for anyone (like me, a woman in a dark parking lot at the airport with a dead battery). I will keep it for charging my cell phone but if you think this will work on a car battery - forget it! I finally got a real jump the traditional way.
Bottom Line: No, I would not recommend this to a friend
There are some brands that are about the size of a cell phone that have short clamps to put on your battery. You can jump-start your car yourself and these do work. I got my 78-year-old mom one and she used it. We have one that works great too. Cobra is one brand but there are a few. It's more expensive but I recommend it.