The jump starter batteries are handy. One of my saddle bags is full, with a jump battery, a small compressor, (12 volt), tire plugs and a couple of bungee cords. Being on the side of the road with a flat tire, or dead battery ain't no fun at all! And running a small compressor off your bike battery will work, and fill your tire, but you just might find that you sucked too much juice out, to start the bike when you're done. "Don't ask"