Today, I came back to my Prius after leaving it for only a few hours. And to my surprise the battery had died. I called someone and jumped the car back to life. Then took the car for a little drive back to my house and turned it off, seeing if the battery would still hold some charge. But i came back out to it 10 minutes later and the battery was dead again. I hooked the battery up to a charger and let it run for awhile. Any suggestions on what i should do?