Apple has issued updates for MacBook, MacBook Pro, and MacBook Air notebook models to fix a rare battery issue. The updates are available via Apple’s software updates page or through Software Update and the Mac App Store.
This update addresses a rare issue on some Apple notebooks where a battery that has accumulated more than 1000 charge cycles may unexpectedly shut down or stop functioning.
Link:
Apple Issues SMC Firmware Update for MacBook, MacBook Pro, and MacBook Air Models [Mac Blog]