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I've gone through old well-answered questions about how to prevent a Mac battery lifespan (Does a low power charger help Macbook's battery, Limiting macbook (usb c) charge level…, Apple recommendations, etc.), and understood that:

  • It's best to stay between 20 % and 80 % (for all lithium-ion batteries)
  • It's not a good idea to use a too-low power adapter (drains the battery)
  • Fast charging is not great
  • Some recommend using AlDente (or just let macOS manage it)

Something I still cannot figure out is if it's a good idea to use a power adapter that is not super powerful to charge slower when the Mac is going to stay wired for several days.

For example, I have a 140W power adapter sold with a MacBook Pro 2021 16' M1 Pro, wired most of the time. When I use it outside I'm happy that the power adapter charges it to 100 % very fast, but when I'm back home and know it'll stay here for several days, I wonder if it might be a good idea to plug it onto a lower power adapter like the 96W or even the 67W (and leave it to charge and stay at 80-100 % for days on it).

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I think you would need to discern between a theoretical and a practical "preservation of battery life".

Would using a lower power adapter, which prevents Fast Charging, help preserve the battery? - Theoretically, yes.

In this scenario where the Mac is plugged in for days on end, there would be a very narrow window at the start of your "several days of staying wired" - where for some minutes it fast charges, which slightly increases the temperature of your battery - which ever so slightly decreases the life time of your battery more than not fast charging.

Would using a lower power adapter, which prevents Fast Charging, help preserve the battery? - Practically, not really.

Would it really matter to you if your battery failed to worked to your satisfaction after 4 years, or after 4 years and 2 weeks? - Especially when you factor in the time you have spent worrying about the life time of your battery and implementing various safe guards.

Using free software such as AlDente to limit charging to 80% when staying wired seems like a simple and reasonable thing to do.

Beyond that, I think spending money on a different, lower wattage charger, is simply not practical. The charger would cost you much more than what you save in terms of having to replace the battery slightly earlier.

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  • Well that's a pragmatic and detailed answer, thanks! I was thinking about it because I'm planning to buy a second power adapter (and would maybe use a 96W for home-charge and the 140W for outside charge).
    – Joan
    Dec 4, 2022 at 13:34

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