TheLaptopJunction

Laptops using AC power adapter identification communicate through a 3rd wire in the DC power cord. The signal arrives at the motherboard through a protective circuit shielding the POST controller from electromagnetic pollution.

Insufficient protection or simply excessive signal pollution can either destroy the protective circuit or the input of the POST controller. In either case, any repair attempt requires the motherboard to be disassembled.

A simple test to check if the above is the case is to test the AC power adapter with an identical laptop. If battery charging resumes the AC power adapter is able to identify itself properly. If the DC jack is also OK – further diagnosis requires measurements at the motherboard.

If laptop motherboard replacement is not an option, it's possible to still charge a laptop battery using a standalone laptop battery charger.

 
Back to the laptop battery charging diagram.