"Doesn't even recognize when I plug it into power" sounds more like a problem with the DC-In jack (supplier example only), being loose or is broken internally, than a corrupted BIOS problem preventing a normal start.
What may have happened is that if the DC-In jack is loose from the motherboard or the +ve pin connection is internally broken in the jack (it happens), the motherboard does not get any power to either charge the battery, so it goes flat or to run the laptop either.
Check if you get a power connected indication on the laptop by plugging the charger into the laptop and gently, stress gently, slowly move the charger plug up and down and side to side in the jack to see if the power light turns on and off. If it does it indicates a problem with the jack.
If it does or even if not, you will have to open the laptop and check if the jack is just loose from the motherboard or if not then whether it is faulty and needs to be replaced. If you have to replace it, most probably you will have to remove the motherboard from the laptop case.
FYI there is no separate CMOS battery in the laptop. The 3V RTC (Real Time Clock - aka CMOS) battery supply most probably comes from the main battery as is the case with most laptops these days and not from a separate coin cell battery connected to the motherboard.