Nice little handheld mobile jump starter for cars. I bought it a while back when my wife had trouble with jump starting car. It worked the first time we used it, very well. No need to borrow life from another car.
But today, when we tried to help someone else jump start his car, it didn't work. According to this Amazon comment, it may not always jump start right away, we may have to wait for 4 minutes for it to charge up the car battery or something. Also, there's this mention of connecting the cables to car battery first before connecting it to the jump starter unit.