Recently, when I leave the PC on after shutting off the car and then come back and start the car, the computer turns off then back on, without going through shutdown or anything. It just started a few weeks ago, before then it stayed running after crank. I'm thinking it's the battery in the car going bad. When I crank the engine, there isnt enough power to the supply so it turns off. Would this be the problem before I go out and by a new car battery?