Some models had a small LED bar that you could check the battery status with, without opening the lid. On older Mac’s (2009-10?), the LEDs were built into the

Some models had a small LED bar that you could check the battery status with, without opening the lid. On older Mac’s (2009-10?), the LEDs were built into the battery. Very handy to quickly check if your spare has more charge than the one you’re using.