MacBooks and MacBook Pros contain lithium-polymer batteries. They’re powerful and should last you at least 2-3 years without issues as long as you take appropriate care of them. However, there’s a really common way to destroy your Mac’s battery if you aren’t careful.
The easiest way to ruin your Mac’s battery is to leave your sleeping laptop unplugged and unused for weeks. You’ll know the laptop is sleeping if you look at the front and see a little light fading in and out.
If you normally just close the lid when you are finished with your MacBook, there’s a good chance you keep it asleep overnight. You’ll also notice that the machine uses some battery power while sleeping (if it’s also unplugged), when you open it up to use it the next day.
If this is a normal habit for you, then be forewarned – If you go away on vacation or don’t plan on using your Mac for an extended period of time (a week or more), make sure you shut down your laptop. You’ll know it’s shut down if the little light on the front is completely off.
Why is this bad:
Long-term sleep is horrible for your battery because the sleeping laptop takes a small amount of electricity to run in sleep, or low power mode. Normally, a Mac will go into a hibernation state when the battery drops below a certain level to protect the battery and your data. In addition, the battery has a small reserve charge to keep it alive when the battery completely discharges.
Here’s the danger – If your MacBook is asleep and it crosses that threshold, it continues to sleep and does not go into hibernation. The battery continues to drain, running through the reserve charge until it is completely dead.
How long-term sleep destroys your battery:
The Lithium-Polymer technology in MacBooks and MacBook Pros does not like to be completely drained. If the battery completely discharges, it will not charge again. After two to three weeks, that sleeping laptop with a full charge is now completely drained (including reserve) and the battery ruined. You’ll know this happened if you didn’t use your laptop for a few weeks and suddenly the battery doesn’t charge anymore, has an “X” inside the symbol in the Menu Bar, or will not run when unplugged.
You can try reseating it, resetting the SMC and leaving it charging for a while but if it went completely dead, it’s not coming back.
What should you do?
It’s pretty simple. To avoid killing your battery, shut down your MacBook / MacBook Pro before going away on vacation. To make it even easier, get in the habit of shutting down your laptop when you are finished with it for the day.