Power supply troubles with my computer?

Considering the motherboard battery is basically a watch battery, it is not going to affect the power available to the machine. There can be many o9ther reasons why this happens. The CPU can be overheating, the hard drive can be faulty, the power supply, or even a faulty DVD or CD drive causing overloading. Even too high a power video card can do this. A computer power supply does NOT have any high current 12v supply present when powered up, it relies on a signal from the motherboard to start these. Most will NOT continuously deliver 4 amps safely. You are better to buy a 12v 4a supply from an electronics chain.