Can anybody give me any tips on how to monitor the internal and external battery levels?
Setting up completely autonomous nodes with the standard coin battery and a solar panel (and maybe an external if needed)
Anybody got any ideas please?
You can make a voltage divider to read the battery voltage.
On our support page we have a function how to read the voltage with a voltage dividerhttp://support.sodaq.com/sodaq-one/battery/
Will this work for a coin battery? I thought that with coin batteries, the output voltage remains quite steady until the battery is basically spent?
This is true for non-rechargeable coin cells.
On the Explorer we use a rechargeable LIR2450 coin cell. Here the voltage is between 4.2V and 3.5V.See datasheet: