Battery health with MacBook Pro M4 Pro closed with external monitor and often charging?

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Battery health with MacBook Pro M4 Pro closed with external monitor and often charging?

I have a MacBook Pro M4 Pro and a Dell U3417W as an external monitor where the MBP is closed for most of its existence. I believe that I must keep the MBP charging in order for it to send a signal to the monitor. When I am not using the MBP I usually put it in sleep mode and disconnect MagSafe. Is harm being done to the battery for all the hours I am using it with the monitor being that it is continuously charging? Or, is it not truly charging because the battery is at 100% most of the time?

I ask because I also have a 2015 MBP where the battery can no longer hold much of a charge. Of course, that is probably because it is so old with years of the same use as described above.

Thanks

MacBook Pro (M4 Pro, 2024)

Posted on Dec 22, 2025 6:01 PM

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Answer 1

Dec 22, 2025 8:04 PM in response to Moriah7474

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.

Any external power supply that provides "USB Power Delivery" (including certain Docks and Displays) must negotiate over the USB cable using USB Power Delivery Protocol, and can not 'force itself' on your Mac. The Voltage and Current are delivered only after your Mac requests and the power supplier agrees to supply power under certain controlled conditions. The computer draws only as much power as it wants, and the computer is in control of the entire process.

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