A reverse-polarity alarm helps ensure safety and prevent improper connections. The Stanley 500A jump starter with compressor also has a handle for convenient portability. I have a dead battery and was really hoping this Stanley Jumpit 1000 would help me out. I also have car tires that need air, along with one that had gotten pretty flat. (My vehicle has been off the road, for a while.) First of all, I got pretty aggravated with the instructions.