First, I have an old Mid 2015 Macbook pro however I had a brand new battery installed last year. Battery has been in good health for most of the time it's been installed. Capacity started dropping heavily over the past few months which isn't totally unexpected. What is frustrating is that it seems to require constant calibration because the capacity it is reporting jumps all over the place. It will read 7000 mah and then 2 days later drop to 6000. I calibrate and it goes to 6500 and then a few days later drops to 5000. I calibrate again and it goes back up to 7000. Is it my old system? A bad battery? What could be the issue? I've been following the 80/20 recommendation of never charging above 80% and never letting it drop below 20% (generally). I plan to try an SMC reset next.
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