advice on charging issue

Hi,

I have a Nexus 6P that I have been quite happy with (more so than with my current galaxy S7 edge). I had two issues with it, though. It was in need of a battery replacement, and the charge port was broken. I bought a new (third party) battery and a new daughterboard (which the charge port sits on). I replaced both parts. But it refuses to charge the new battery.

Thought I might have damaged the daughterboard while installing it, so I got yet another one and installed it. Same problem.

It might be the third party battery that is defective. But I'm hesitant to buy another part for this phone, so I'm asking for some advice.

Even if the battery is defective, should it not be possible to run it plugged in to a charger? That is not the case.

While I still had some charge left in the battery, I checked readings from AccuBattery. It seemed to draw power from the charger intermittently just when it was plugged in - only to drop to below 0 after a few seconds. Various websites recommended to wipe the system cache as remedy for charging problems, so I also did that before the phone died. But it did not help.

Perhaps, instead, something is wrong with the motherboard, not the battery? Spending more money on another battery will then be useless.

Does anyone recognize any of this?

Advice and suggestions are greatly appreciated!

Pär Larsson,
Sweden