RTC battery CR1220

2-10PCS ML1220 1220 3V Li-lon Rechargeable Battery CMOS RTC BIOS Back Up Button Coin Cell For Laptop Motherboard Replace CR1220 - AliExpress

RTC Battery Low Warning Battery Replacement

1x CMOS Battery.

CMOS RTC Battery For ASUS ROG STRIX GL702VS SERIES CR1220

Rome Tech CR1220 CMOS Battery for MSI GS75, Asus Q302L - Laptop Backup BIOS RTC 3V CR 1220 Battery with 2 Wire Long Cable Regular

Rome Tech CR1220 CMOS Battery for MSI GS75, Asus Q302L - Laptop Backup BIOS RTC 3V CR 1220 Battery with 2 Wire Long Cable Regular Connector (1-Pack)

Most RTCs use an external 32kHz timing crystal that is used to keep time with low current draw. And that's all well and good, but those crystals have slight drift, particularly when the temperature changes (the temperature changes the oscillation frequency very very very slightly but it does add up!) This RTC is in a beefy package because the crystal is inside the chip! And right next to the integrated crystal is a temperature sensor.