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| The coin cell battery (sometimes referred to as CMOS or RTC battery) helps maintain system settings when your device isn't connected to power. |
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| Some signs you may need to replace the battery: |
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| * The date and time are incorrect after your Mac has been turned off for an extended period of time. |
| * Your Mac isn't waking up from sleep or hibernation on schedule. |
| * Your Mac is experiencing startup problems. |
| ***Before starting this repair***, read through Apple's troubleshooting guides on [link|https://support.apple.com/en-us/102969#power2|startup issues|new_window=true] and [link|https://support.apple.com/en-us/102969#power1|intermittent shutdown or system instability|new_window=true] and try the solutions that don't require taking apart your device. |