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Birdie 01-12-2010 08:53 PM

Battery capacity drops every time after calibration?
I have a 2 months old macbook plastic unibody version. So far I've done two calibrations, draining the battery until it shuts down itself and charging it until it reaches 100%. After the first calibration, the battery capacity dropped around 100 mAh from 5300 to 5200. Just after yesterday's calibration, the battery capacity dropped another 100 mAh or so to around 5100 mAh. The battery capacity also increases by small amounts from time to time during regular uses. Now my battery is at 94% health with 16 charge cycles. Why is calibration killing my battery?

cwa107 01-12-2010 08:57 PM

It's not. Batteries are not an exact science. Unlike the gas tank in your car which has a float and a sensor to judge the position of the float, there is no way to accurately meter the capacity of your battery. Those ratings are little more than "educated guesses" based on your usage patterns.

Over time you will likely see these numbers fluctuate as the SMC learns more about your battery's discharge patterns. For right now, I wouldn't sweat it. Now, if you see the battery health at less than 90%, that would be a different story - for now it's fine.

Birdie 01-12-2010 09:19 PM

What's the warranty for macbook battery? I heard something about 80% and 300 charge cycles, but I can't find the exact Apple webpage that talks about battery warranty.

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