At that age it could be the other age issue. This is a 17 inch laptop and if the owner was a student the strain of travel and flex of the boards means we get to swap the motherboard for a test. If the board swap fails (which it rarely does) then you look at the cables and such coming off the mainboard for breaks or tears.
I already noted the CMOS Battery so no need to repeat that.
And so far no Dell requires the big battery to power up and run.