I thought I had the dual-battery system all finished but I was wrong. I’ve never understood what’s been going on with the voltmeter. I assumed that it was probably connected to the dual-battery controller which was responsible with informing the display what to show. I decided to pull it apart and take a look at how it works.
Having a look at the circuit, you can see why I was confused.
Both the meters are looking at the same battery! I’ve fixed it up and the new circuit looks like this.
Now I can now see the voltage of each of the batteries and I don’t need to turn on accessories to get a reading. Hopefully the battery saga is now over.