Hi.

I have Dell Vostro 3400 that will auto shutdown (only on battery though) after unplugged from AC. Well, not exactly after unplugged. If I left it idle and did not touch anything after unplugged, it will last about 5-6 minutes, but if I directly open any software after unplugged, it will shutdown completely. 

At first I thought it was battery problem, but when I restart, the battery percentage did not show any symptom of bad battery such as drastic dropped in percentage. 

Restart in safe mode but the problem still happen.

Found nothing in BIOS, and Power Plan looks normal. I don't think it's overheat problem as well.

The motherboard had been replaced once. Could it be the motherboard??