I was a bit concerned this weekend when a ‘service battery’ notice popped up on my MacBook. End of life? A bit of online research led me to a simple method for recalibrating the battery (eg. see maketecheasier, skipping the SMC reset section).
All I needed to do was get the machine charged up, use it for a couple of hours on power and then unplug and keep going until it put itself into a preservative sleep and leave it there for at least five hours before fully recharging. I tend to use the Mac on power most of the time so it felt odd just letting the battery run all the way down. I didn’t have to use the device all the time – just keep an eye on it to prevent it going to sleep early.
Seems to have worked. Certainly for now, the warning message has gone away.