Hi,
you can check https://openrepos.net/content/radekp/battery-monitor for battery monitor application done by me.

It draws graph for charge_now values. Unfortunately the value refreshes quite seldom - so not very useful for short term measurements, but you will get pretty accurate graph e.g. if you manually refresh after a few hours.

Btw battery on my Jolla on 2G takes 7 days to discharge.