My Asus laptop has a good battery that lasts for 3 hours, when i am gaming or using a heavy software, it is alright while plugged in, but when i unplug it, it lags for like 5 seconds, then it suddenly powers off, but when am not using a heavy software, or gaming, it lasts for the whole 3 hours. Also, after it powers off, i can switch it back on for other things, but not game. Please help, do i need a new battery? Is it a settings??