I have a mid-2009 white MacBook. About a week ago, I switched the aging and failing battery for an identical new battery I got off eBay (supposedly original part and new – looked legit both in description and packaging).
After switching the battery and resetting the SMC, a fully-charged battery reports six hours of available battery life, the way it should. But the battery runs out after only three or so. Pretty much the same battery life I got out of my old battery.
Could there be something I'm doing wrong software-wise here, or is it likely that I got a shitty used battery which was polished and made to appear new?
Best Answer
The first step is to look at the detailed battery information from the System Information/System Profiler for each battery.
Pay attention to the Full Charge Capacity and cycles for each battery.
The second step (assuming my guess that you have a non-unibody Mac where the battery is user-replaceble - swappable without removing the bottom of the Mac) is to run a simple calibration charge cycle on the new battery (and followed by the old one perhaps to compare). Once your computer gets to know the new battery (it guesses based on average battery performance until it determines the chemistry particular to each battery that gets used over time).
The third step if you really want to measure everything on both batteries is to use the pmset -g pslog command to document each battery as it powers your Mac from full to the low power shut off point.
Here is the relevant section from the man page linked above: