I once had exactly the same problem with a Lenovo and it was because the BIOS I'd flashed wasn't quite the right one for the motherboard. Often a single Lenovo model can use two different motherboards, depending on when it was built. For instance, an L13 Yoga can be of Type 20R5 or Type 20R6. Check very carefully whether the BIOS you have used was the correct one for the specific motherboard you have.

The power from the charger is reaching the mother board - that's what you're measuring on the red wires.
There's a pinned thread here https://www.badcaps.net/forum/troubl...arging-circuit that explains where things go from there.

Hi,

Please can anyone shed some light on why my Dell Vostro 3578 is giving the following BIOS error: 'The primary battery is not identifiable and this system will not charge this battery pack.'?

The problem is not the battery - I've tried three different identical ones, all Dell OEM. They all work perfectly in other systems (different models, though) whilst giving the same error in the Vostro.
The laptop will run happily from the battery if it is charged and Windows accurately reports the charge level, proving that the communication between the laptop and the battery...