Don,
The led lights on the panel only tell you battery voltage. That is a measurement but definitely not a true reading. It is like reading your fuel tank level without being able to know how many miles you have traveled.
To get a much better reading on your battery level especially with the extra batteries and your desire to do some boon docking I recommend the
Bogart TM 2025 RV meter.
It uses both voltage and current measurements so the same as tank level and miles driven to give you a much better status on the battery.
The rule of thumb I use is to keep my batteries above 50% usage. This meter helps me do that.
Good luck and safe travels.