We've noticed that the RTC onboard battery has an extremely limited life and results in the loss of time. The two options that we will be debating on during our next meeting is whether to keep the RTC, replacing the battery by soldering (danger), or buying a new unit with replaceable battery. Adafruit makes a RTC with the same IC (DS3231) which means there would be no code modifications needed. A perfboard or full PCB would be needed to add as the headers do not line up. The replaceable CR1220 battery will keep the RTC running for over a year in storage. Link to product below: www.adafruit.com/products/3013
We have also used the same RTC breakout from adafruit before the ones used at the workshop. So it is a direct plug and play replacement that works well, it's just twice the cost as the ones being used now.