How to maximise battery life when using MacBook Pro on high load? Cable or battery?

That computer is a battery-CAPABLE device. It is not optimized as a battery-operated device. (It is NOT an iPhone.)

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, even with the power adapter connected, the charged state may even decline during stressful work.

When used only on battery, your computer has no extra cushion of power, and may 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 could be somewhat slower) when no AC sources are at hand. Your Mac will NEVER over-charge.

If I post information that is not my own writing, I do try to attribute to the source when I can.

When I find that I am posting my same answers over and over gain, I do indeed save my answer and sometimes additional notes, re-read it, and copy and paste, and apply edits as appropriate. What I posted is MY writing, personalized for the specific situation from the notes I have stored.

If there is something in what I posted you disagree with, please let Readers know. They call this Apple Discussions, that is, a dialog with differing points of view.

?Are you using Battery Health Management?

Batteries - Maximizing Performance - Apple

About battery health management in Mac laptops - Apple Support

I'm using my Mac book pro M1 Max in the same way of the author of the post but I noticed that I'm at 94% of battery life and only 12 cycle from July 2022. Seems the battery died more quickly when the MBP is always AC connected...

Batteries are a wear item, like the soles of your shoes and the tires on your car. Their expected lifetime depends on use (as reflected in Charge cycles) and also in the passage of time, used or not. After a while, you should expect to have to replace the battery.

Battery life also depends on two factors you may be able to control a bit better. Lithium polymer batteries deteriorate when they get too hot, and when they are subject to very deep discharge. These should be avoided when possible.

Despite using these batteries in millions of Apple devices, there is still an increased amount of of randomness in exactly which battery will fail when.

Apple SUGGESTS (but does not Warrant) that your battery MAY last as long as 1000 charge cycles, provided all other factors are well-controlled.

Apple uses the criterion that a battery that doesn't to hold 80 percent of its original charge capacity should be serviced, and likely replaced.

When designing systems, that 80 percent rule is intended so that, over a Very large sample of devices, almost all will be able to achieve their 'mission' -- still have at least 80 percent capacity at the three-year mark.

Thanks for your copy and paste