How to resolve my mac dying at 75% battery?

Solution 1:

Typical life expectancy ("Maximum cycle count") is 1,000 cycles. From Apple's webpages: "Your battery is designed to retain up to 80% of its original charge capacity at its maximum cycle count. For best performance, replace your battery when you reach its maximum cycle count."

In short: your battery has been heavily used and needs replacing. I'm surprised that the OS hasn't given you a notice that the battery needs servicing. It just isn't reliably holding charge.

Apple defines one cycle as a complete 100% - 0% discharge; and this also includes partial discharges cumulatively, so a discharge to 75% (before recharging) is 0.25 towards the next cycle.

If the data is to be believed, in six years, you've managed an impressive average of a complete discharge from 100%, then a recharge and another 50% discharge, every day.

There's nothing else that can be done to improve it.

Solution 2:

There is a Battery Recall Program for some MacBook Pro 15" Mid 2015.

You can check if your device is eligible on https://support.apple.com/15-inch-macbook-pro-battery-recall

Solution 3:

Distinguish your battery cells actually holding that amount of charge from the battery controller IC's estimate of charge, which appears to be off. Due to the very flat discharge curve of LIon cells, charge is estimated by measuring the charge flowing into and out of the battery, and estimated charge capacity will be updated over time as well. The controller may have failed to properly track charge, or to update its estimated charge capacity as quickly as it has degraded, OR the battery may be self-discharging.

Suggested: feel the battery, especially just before and after charging, and perhaps 15..30 minutes in. Is it hot? If so, I will suggest treating this as a potential safety or equipment damage issue.

Your battery cells are worn out and need to be replaced.

When ordering a replacement battery, beware battery packs that were manufactured around the same time as the original.

Also beware "jump-started" LIon batteries. I've seen the aftermath of that. Once an individual cell discharges below (IIRC) 1.4V, the copper anodes start to go into solution. The battery controller thus disables the battery pack -- but this can sometimes be reversed by "jump-starting" the pack. Charge them up: copper plates out as nucleation sites, then lithium whiskers begin growing whenever the battery is charged. Eventually, they may puncture the cell membrane and you can have a battery fire.