Hi All My Macbook keeps just doing a hard shutdown when on low battery. Once the battery indicator gets down to the red with about 15 to 20 mins left the machine just shuts down no warning indicator. I want to re calibrate the battery but because of the way the machine shuts down IE: Not going into sleep mode, how can I recalibrate ? Battery has about 260 cycles on it, but could this issue be the battery going ? Just done a PMU reset on it and charging it back up at the moment so I can run it down and see if the PMU reset has achieved anything.