Battery capacity

Batteries are considered Consumable Products. Over time it will degrade to a point where it needs to be replaced. The usage is normal as the capacity will go up and down all the time and never stay always at 100%. Apple Batteries are rated for 1000 Full Battery Cycles and / or 80% Capacity before needing Evaluation or replacement.

For additional reading on Battery and Apple Computers this link may help. About battery health management in Mac notebooks and especially for the M1 and Big Sur If battery charging is paused or on hold on your Mac

A feature introduced into Big Sur was to preserve the number of Full Battery Cycles - there was an Algorithm coded into the macOS. It is perfectly Normal for Big Sur to Pause / Suspend charging the battery beyond 80% and hold it at that level. One can nudge / over-ride this by clicking the Battery Icon on Desktop Top Bar and allow charging beyond 80%. From observations, it will Pause / Suspend again once reading 90%. Same procedure to over-ride and will charge to 100%

jindran wrote:

,,, I may left it in my car during this summer couple times, but I always waited it to cool down before usage.

,,,

Very high temps as one sees inside a car is not good for laptop or phone batteries whether the device is running or not. The specified storage temps for the MacBook Air, i.e. temperatures when not in use, are −13° to 113° F (−25° to 45° C). The interior of cars in the summer even in temperate climates can easily achieve 55-60 C, especially if it is a dark color or has relatively large window area.

With that said, even when the battery capacity reaches 80%, the laptop does not simply stop working, it just doesn't run as long on battery. Variability in battery production can be quite wide and is not a absolutely precise thing.

If you truly believe that this is an issue, set up an appointment at the nearest Apple Store or at an Authorized Apple Service Provider and have them check it out.

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