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USB type C monitor charging

Hi everyone, I'm using a DELL P2720DC monitor and I just found out that I can connect my MBP to the monitor without HDMI, just with a USB type C cable. It also provides charge to my Mac. This is great, but it's also a problem: I'm afraid that when the charge is at 100%, it damages the battery, and I can't disconnect the cable because I'm using the monitor.

How can I solve this? Do I have to be afraid about the "always on charging" mode in my Mac, or is it ok to continue working with the monitor plugged even after the Mac is full of charge?

Anyone knows how to stop the charge on macOS?

Thank you in advance!


MacBook Pro 13″, macOS 11.0

Posted on Sep 24, 2020 3:30 PM

Reply
Question marked as Top-ranking reply

Posted on Sep 24, 2020 5:10 PM

Your computer performs best when connected to AC power. It can use the full output of the Power Adapter AND when doing especially challenging work will also freely "borrow" power from the battery. In some cases, the charged state may even decline during stressful work.


When used only on battery, your computer has no extra cushion of power, and will perform more slowly. However, for ordinary non-stressful tasks this may not be objectionable (possibly not even noticeable.)


In general, you should ALWAYS connect AC power when it is possible to do so, and only run on batteries (which will be somewhat slower) when no AC sources are at hand. There are three micro-controllers cooperating on battery and charging issues, and your Mac will NEVER over-charge.


USB-C Power delivery is always a negotiated charge level. A power source can Not "Force itself" on your Mac at any level higher than 5 volts at 500 milliAmps, which any device can easily ignore.


5 replies
Question marked as Top-ranking reply

Sep 24, 2020 5:10 PM in response to GiovanniPerre

Your computer performs best when connected to AC power. It can use the full output of the Power Adapter AND when doing especially challenging work will also freely "borrow" power from the battery. In some cases, the charged state may even decline during stressful work.


When used only on battery, your computer has no extra cushion of power, and will perform more slowly. However, for ordinary non-stressful tasks this may not be objectionable (possibly not even noticeable.)


In general, you should ALWAYS connect AC power when it is possible to do so, and only run on batteries (which will be somewhat slower) when no AC sources are at hand. There are three micro-controllers cooperating on battery and charging issues, and your Mac will NEVER over-charge.


USB-C Power delivery is always a negotiated charge level. A power source can Not "Force itself" on your Mac at any level higher than 5 volts at 500 milliAmps, which any device can easily ignore.


Sep 24, 2020 5:08 PM in response to Grant Bennet-Alder

A charge cycle is ever-so-slightly destructive to batter longevity. When operating as designed (and not using Battery Health Management) battery charge level is allowed to decline to about 92 percent level before initiating a recharge cycle to top up to about 99 percent.


————

Catalina software 10.15.5 for MacBook Pro with T2 chip (2016 models and later) includes a new feature called Battery Health Management. Based on your usage patterns, this widens the hysteresis to initiate a charge cycle at a lower level, and stop before 99 percent.


About battery health management in Mac notebooks - Apple Support

https://support.apple.com/en-us/HT211094


This relaxes the set points around re-charging (based on your usage patterns) and can improve long term battery lifetimes. When active, recharging may stop short of 100 percent charged.


USB type C monitor charging

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