On some older macs if you take the battery OUT the processor will be throttled by 50% because of charger limitations. I'm wondering if that applies to a 2012 MBA too. My Air has been running noticeably slower than it used to. The battery health is showing 2.7 years old, 326 cycles and only 42% health. Could this be the reason it's running slow? If not I suspect Yosemite because it seems to lag a lot more since I installed Yosemite.