MacBook Pro battery degradation with monitor charging?

PeregrineClarke wrote:

The BenQ model I have doesn't support switching the power delivery off through USB C

The power delivery management occurs inside the MacBook Pro via the MacOS. The BenQ external power supply does not decide when to start or stop charging the MacBook Pro.

So activate MacOS battery health management and eventually (it may take some time) it will target approximately 80% maximum charge. Depending on which options you select in System Settings, it may charge past 80% at times, including during calibrations or to establish a baseline. You may also be able to specify charging to 80% in those Settings. This will work the same whether you are using the power supply (140W MagSafe 3) that comes with your laptop or the BenQ; however you should check how many watts that BenQ will be able to provide to make sure it is adequate for a 2026 MacBook Pro M5 16".

I have been charging MacBook Pros for many years now with power delivery via a dock. Apple's battery health management still works and tends to stop charging the battery at around 80% charge level.

Apple calls the external device shipped in the box a Power Adapter. It is not a charger.

The CHARGER is inside the MacBook Pro, and is completely under program control. Your Mac accepts some power when needs to run, and accepts more power when it intends to charge its internal battery. A power source like the Power Adapter or certain Displays can not 'force itself' on your MacBook Pro. Only the algorithms inside your Mac can decide when is a good time to charge the battery. Your Mac can NEVER be over-charged.

No this will not cause battery degredation. The battery is protected against over charging so it will not overcharge when using a display/docking station