When should I charge my MacBook Pro battery?

Jejoby wrote:

I recently bought a new MacBook Pro. I want my battery to last as long as it can. When should I charge my battery: when the battery is completely dead, or when it still has some charge in it? Does it make any difference?

If you are near the mains leave it plugged in, if you need portability then run on battery.

Batteries - Maximizing Performance - Apple

https://www.apple.com/batteries/maximizing-performance/

Determine battery cycle count for Mac notebooks

https://support.apple.com/en-us/HT201585

About battery health management in Mac notebooks— introduced with macOS10.15.5

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

Jejoby Said:

"Battery Charging: I recently bought a new MacBook Pro. I want my battery to last as long as it can. When should I charge my battery: when the battery is completely dead, or when it still has some charge in it? Does it make any difference?"

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Keep a 40% Charge at Minimum:

You should never let your battery go dead, as it will affect its health, making it more vulnerable to failure. So, be certain to always have a 40% minus charge to it, to maintain a reliable power source: your battery

Leave your computer plugged in when convenient to do so. Neither your computer nor your battery will be damaged by leaving it plugged in. Leaving it plugged in reduces the rate of accumulation of battery cycles.

Edit:

40% minimum charge