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my main machine is a 2016 15" MacBook Pro and, working in print graphics, I usually have it connected to an external display (as of today, a Huawei MateView 28.2in).
This display has 65W power delivery and, when attached, it keeps the Mac's battery continuously topped off. This practice is known to wear the battery so I was wondering whether it was possible to have the screen connected AND not charge the laptop unless I tell it to.
Maybe there is some Terminal command to manage that?
Thank you

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  • When you say “manage that” do you mean you want a command line API to change settings in a specific huawei display?
    – bmike
    Dec 7, 2021 at 11:13
  • In general I would be happy with just turning off/on Power Delivery for any connected display, but if one cannot do it and needs to give specific instructions to a specific display, also that is good. Dec 7, 2021 at 11:24

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Sounds like you’ve read most of the general advice.

We have had machines like yours in the shop and we set quarterly reminders to unplug them all one night and let the batteries drain.

Once a year, we try to take all the portables in storage out and charge them to 75% and then power off to prevent deep discharge / low voltage failure, get them in averaging 50% charge for “storage”.

I’m not convinced we prevent much repair since some batteries just don’t last the 1000 full charge cycles whether we baby them or just let them ride.

I’m saying all this, since I know of no way via command line to influence charging. The newer macs slow down charging but that’s enabled by default, has an easy graphical switch and not some hidden / semi secret command.

Anyone interested in delaying the eventual need to remove a rechargeable battery and/or replace it should update to 10.15.5 or later and enable optimized charging. The rest should set reminders to avoid empty and always full batteries by draining and then charging them several times a year when in service.

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  • General advice would be to never let them stay attached to charger when reaching 100%, almost never charge them above 80-85%, try not to get them below 20% too often. I had my battery substituted 2 years ago and now I'm at 86.1% health after 225 cycles. My battery will for sure fall below 80% before 1000 cycles. This display has a Display Port adapter as an alternative, will try that. Dec 7, 2021 at 11:53
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    Ideally you are correct @NotationMaster - just like a hyper miler can sacrifice convenience and acceleration to get optimal distance per volume of fossil fuel, in practice, we often depart from ideal due to considerations like limited time and attention. Really, it's super rare we have to swap batteries on Macs and are delighted to do so when needed to keep machines in service at work. Home it's harder since you don't see the bulk response and any failure is all you see.
    – bmike
    Dec 7, 2021 at 16:37

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