DWM1001 Low Battery detection

Hello,
I am currently using the MDEK1001 with the DWM1001-DEV boards. The Tag is powered by rechargeable 16340 batteries. I want to know when to send the Tag to recharge.

Do you have an idea of how to add a low battery detection, and display the status via Shell Command and/or LED?

Thanks,
A.Roque