Perhaps the most vulnerable part of the laptop or notebook is where the power cord plugs in. It has as few as 3 tiny pins holding it into the motherboard, which can be the most expensive part of the laptop.

Your dog or child bumping the jack when it's plugged in, standing on the cord when you stand up with the computer, flipping it backwards on the table... all these things can break the power jack. You can tell it's broken because the laptop won't charge the battery & it shuts down when the battery discharges.

The fix is to either 1) replace the power jack with a new one, requiring complete disassembly first, the least expensive option; or 2) replacing the motherboard itself, of course also requiring complete disassembly first, the most expensive option.