The GPS has a built in real time clock, which can keep track of time even when it power is lost and it doesn't have a fix yet. It can also help reduce fix times, if you expect to have a flakey power connection (say you're using solar or similar). To use the RTC, we need to install a battery. We provide the holder but the battery is not included. You can use any 12mm coin cell - these are popular and we also carry them in the Adafruit shop.

Normally, if the GPS loses power, it will revert to the factory default for baud rates, configuration, etc. A backup battery will mean that those defaults will not be lost!

The backup real-time-clock circuitry draws 7 uA (0.007 mA) so a CR1220 will last 40mAh / 0.007mA = 5,714 hours = 240 days continuously. The backup battery is only used when there's no main 3V power to the GPS, so as long as it's only used as backup once in a while, it will last years

This guide was first published on May 17, 2016. It was last updated on May 17, 2016.

This page (Battery Backup) was last updated on Nov 07, 2020.