MAX31343
Production
The MAX31343 is a low-cost, extremely accurate, I2C real-time clock (RTC). The device incorporates a battery input and maintains accurate timekeeping when...
Datasheet
MAX31343 on Analog.com
Hardware: AD-POMON-SL
Goal: RTC can work 24 hours and record power quality events occur time
Problem Description:

Troubleshooting steps were taken by myself:
YongLawrence The RTC can be connected to the battery. You can take a look at the design support files. On page 5 from the schematic file, you can see that BT1 is connected to the RTC. If you look in the BOM file you have there a recommended component "MS621FE". You need to install that one or an alternative on the main board. To do that you have to unscrew the daughter board from the standoffs and disconnect it from the connector. After installing the battery, you can install the daughter board back to its place.
Hi REtz , so we can just solder battery MS621FE on the board (red circle)?

YongLawrence Yes.