I'm trying to determine whether my current solar system is adequate or if I need to add more panels/batteries. Currently I have 2 6 volt lead acid batteries. I have 300 watts of panels 40 amp con...
Furnace is your main draw. You can use a DVM to measure voltage (battery has to be completely at rest) hence look up SOC and then Ah used. There are inexpensive volt/amp measuring devices on up to better battery monitors.
I use to just check voltage and based on prior experience with the rig I was an adequate "battery monitor".