What does the BIOS battey do?

CMOS batteries power code that runs before the operating system is loaded in a computer. Common tasks completed before your operating system loads are activating the keyboard, loading the system drives and setting the system clock. Because the system clock is controlled by a CMOS battery, one of the most common methods of identifying CMOS battery problem is noticing that your computer has a problem maintaining the correct time. A dead bios battery usually wont stop a laptop from booting

This could be an host of issues any one of which can cause this so lets start with the basic. remove the laptop battery and disconnect the power then hold down the power button for 60 seconds. then reinstall the battery and plug in the power and boot the laptop. if it works it was a case of static discharge if there is no joy lets move on to the ram . Remove one stick of ram and try to boot the laptop if it doesnt boot then move that stick to a different dimm slot. and try to boot again if the laptop boots it means one stick of ram was bad if not then switch out and test with the other stick keep trying until you have tried each dimm in each slot . If you have no joy then we move on to the APU. try pluging in an external monitor. If it works then your LCD screen is bad and will need to be replaced if it doesn't work then the issue is probably with the APU