BATTERY HEALTH
I have used a Macbook pro M2 since February. I don't know why my battery health is decreased to 90% but the cycle count is only 27 and I don't use my Mac frequently (just 2-3 times a week).
MacBook Pro 13″, macOS 12.6
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Cycle count is unimportant to battery health basically. If you left it on charge for years, like l I do my 2016 MBP, cycle count would be 1 (or near that) but battery remaining capacity would still degrade .
90% is still good and since battery deterioration is non linear, it could sit at that for months; batteries still age even if never used. That's just the way they work.
Let the battery circuitry manage the battery and replace it when it gets to 80% as Apple recommends for best continued performance.