Permanent eggshell mode use killing battery?

The advice you received from the Apple store is incorrect or you misunderstood the advice provided.

You are asking about "Clamshell" mode. There is no danger to the battery. You can leave it plugged in without damaging the computer or the battery.

Why not just use it with your connected monitor as a secondary display?

That would give you a much better workaround with an extra desktop as a nice bonus. 😉

muguy Said:

"My MacBook Pro has been continually plugged into the mains for more than 4 years, no issues.”

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Just for Thoughts:

Try unplugging it, seeing if the battery drains while it is not charging.

My MacBook Pro has been continually plugged into the mains for more than 4 years, no issues.

mr fish wrote:

Your original battery is still good after 4 years?

I have several Macs I leave plugged in and they do not have battery problems after many more than 4 years.

ben_jackson Said:

"Permanent eggshell mode use killing battery? [...]I am told at the Apple Store that keeping the MacBook permanently plugged in eventually kills the battery[...]."

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Use a Projector:

I'm aways using a projector (for using iTunes and such). It has worked fine for me for years. It is a Brookstone one, and projects small on a screen, and use off the wall. So, consider doing the same.

A Battery Going Dead:

All batteries are prone to failure, and will eventually ware out. That's just the way it is. :(

A projector is a brilliant idea! 😉

Your original battery is still good after 4 years?

My 2016 OEM battery has been at 89% capacity for the last several months. All of 2021 I think.

Yes. The original battery is still good.