External monitor is charging MacBook M1

Please don’t take my comment out of its context, I have many certified USB PD cables and devices (because I repair and diagnose them) so when I say that a monitor only charges at 5V while also providing video output, I think I know what I’m talking about.

The accepted answer here is half right. The reason why your battery health has dropped a lot is that USB-C PD still has to match what the laptop requires. Let's say you have a 97W 16' MBP with USB-C ports. It requires a 97W/100W charger to use and charge at the same time. Usually in the higher wattages they use USB-C at 20.5 Volts. But USB-C PD can actually work from 5V up to 20.5V. So sometimes monitors may not be able to reach those high voltages but will have 5V or 9V PD. When you don't supply the correct voltage and or the correct wattage for a laptop, it will try to use internal converters to make up the difference, which means the laptop will 'charge' but not at the correct rate - and then you may be using it at the same time which will put extra pressure on the BMS and power supply. This is bad because this generates more heat. This is also bad because the battery has to do extra work instead of simply just charging if it had it's expected Voltage or Wattage. You can have power supplies that provide over the limit but you shouldn't use power supplies (also from monitor USBC PD as well) that don't provide the minimum voltage or amperage. If you don't have the minimum it may still work but it's not good for your laptop. I have an MSI monitor that has a USB C connection. It provides video over USB C but it also tries to charge the device connected. But the USB C port on the monitor maxes out at 5V/3A, that's 15W. So really the only device that should be connected to the monitor to use as a charger is something like a tablet or a chromebook, not a laptop.

thefakeandres wrote:

I have an MSI monitor that has a USB C connection. It provides video over USB C but it also tries to charge the device connected. But the USB C port on the monitor maxes out at 5V/3A, that's 15W. So really the only device that should be connected to the monitor to use as a charger is something like a tablet or a chromebook, not a laptop.

5V/3A (15W) is the amount of traditional 5V USB power that all USB-C cables are supposed to support.

USB-C Power Delivery requires the use of cables that have embedded chips to tell the devices connected to them that the cable can safely carry more power. If you have two devices that support USB-C Power Delivery – but use a NON-Power-Delivery-rated cable to connect them, I wouldn't be surprised if

• The devices refused to transfer power at all, or
• The devices fell back to 5V/3A (since they have no way of knowing if the cable can safely carry more than that)

My advice, charge the Mac with the included charger and don't add any 3rd part apps or hardware.

The Mac's battery circuitry is designed to take care of the battery and the charger is a part of the whole. Human micromanagement of battery charging is a waste of time and effort and will never replace how well the Mac takes care of itself.

Charge it when needed, use on battery when portable and let the Mac and its charger take care of the details.

Turn battery optimization on and leave it that way. It doesn't not harm the battery to be "on charge" 24/7.

Is this going to affect the battery health on the long run?

No.

I have a friend who suggested to use third app like Aldente to save the battery health and keep it between %20-%80.

Don't use such things. They are not necessary and cannot possibly help.

Other friend suggested to use USB-c to HDMI cable instead of the thunderbolt, this way I can prevent the Mac from being charged by the monitor and charge it by its adapter.

There is no need to do that, and it's perfectly ok to charge your Mac from an external display. Excerpted from Identify your Mac power adapter - Apple Support:

"If your Mac uses USB-C to charge, you can charge your Mac laptop with any USB-C power adapter or display."

I need your honest advice, I like my Mac and need to take care of it.

Don't take my advice. Don't take your friend's advice. Take Apple's advice: Batteries - Maximizing Performance - Apple

Hi,

I recently bought an MSI 34-inch curved monitor and started using it with my 13-inch Macbook Pro M2 2022 with Thunderbolt. My laptop's overall battery health dropped from 95% to 92% within a month.

I plan on using either (DP to get full 165Hz refresh rate or HDMI) to USB C cable to avoid further decreasing battery health within a short time.

If you come across any other choice, Please do let me know.

Thanks.

The Apple link you provided doesn't say what you claim it says. Just because you can use any USB-C to charge, doesn't mean you should leave it plugged in and charging 100% of the time, which is what charging through a monitor will do. I read through the advice and it doesn't say anything about whether leaving it charging all the time is ok. If anything, it implies that it shouldn't be 100% charged at all times:

"Apple Watch Ultra can further reduce time spent at high states of charge by learning when to charge to an Optimized Charge Limit and when to allow for a full charge."