About MacBook Air SMC Firmware Update 1.8
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.
Your computer's power cord must be connected and plugged into a working power source, or your battery must be at least 25% charged.
When your computer restarts, a gray screen will appear with a status bar to indicate the progress of the update. Your computer's fans will run at full speed during the update but will return to normal speed once the update completes. Do not disturb or shut off the power on your computer during this update.