[guenthert]

> But there is no way to know how much juice is left in the BIOS battery,

True, but its voltage can be used as an estimate. Most PC MB still around monitor the supply voltages, some also of the battery feeding the RTC. If you have the (Debian) package 'lm-sensors' installed, look for

    sensors[<pid>]: Vbat:           +2.91 V  (min =  +2.70 V, max =  +3.63 V)  ALARM

in /var/log/syslog.

[riobard]

Ran `sensors` and it only shows CPU core temps. I guess my MB does not report RTC battery voltage?

[guenthert]

One thing are the sensors, 'nother thing is the software. Have you configured the lm-sensors package (by running `sensors-detect`) yet?

https://hwmon.wiki.kernel.org/lm_sensors also has a FAQ.

[riobard]

Yes I did run `sensors-detect` previously and just to be sure ran it again. No voltage sensors on this box unfortunately :(