Apple has released a new SMC firmware update for the MacBook, MacBook Pro, and MacBook Air. “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,” according to Apple. This applies specifically to older batteries, but the update is recommended for all MacBook models.
You can find this new firmware update in the Mac App Store or download it directly from Apple’s website.
Source: Apple Support.