Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Totally Useless

Tried using this to restart my battery after leaving the rear door open over the weekend. Followed the instructions to the letter, the unit gave me indication that the car battery was fully charged after about five minutes. I tried to start the engine, but the car would not start. Left it in for another 20 minutes just to be safe, tried again and the car would still not start. As a battery booster it's totally useless but it does make a great door stop.