Apple released MacBook Air SMC Firmware Update 1.2 which adds compatibility for the latest service replacement batteries.
The SMC is a micro-controller on the logic board that controls the power functions for your computer. The SMC controls various functions, including:
• Power and thermal management, the Sleep LED, and battery.
• Controlling the fans, supporting Sudden Motion Sensor, ALS, and the power switch.
MacBook Air SMC Firmware Update 1.2 is available via Software Update and also as a standalone installer.
More info and download link (623KB) here.