If you bought a refurbished device, the battery is used. Stocks are stored and batteries are not used for some time and may require battery calibration.
Without calibration, the battery percentage reading will be incorrect, and your device may behave oddly - shutting down suddenly even though the new battery “reads” half charged, or working for hours when the battery reads nearly dead.
For phones and tablets:
- Charge it to 100%, and keep charging it for at least two more hours.
- Use your device until it shuts off due to low battery.
- Charge it uninterrupted to 100%.
For laptops:
- Charge it to 100%, and keep charging it for at least two more hours.
- Unplug your laptop and use it normally to drain the battery.
- Save your work when you see the low battery warning.
- Keep your laptop on until it goes to sleep due to low battery.
- Wait at least five hours, then charge your laptop uninterrupted to 100%.
Apple MacBooks with Thunderbolt 3 ports running macOS Catalina 10.15.5 or newer have a battery health management feature that can prevent the MacBook from charging to 100%. If your MacBook has this feature, turn it off before beginning calibration.
It’s best to perform this process periodically (about once a month) to ensure that the battery remains properly calibrated throughout its lifespan.