Calculating Battery Usage with Solar Panel

[rbkinder]

I am interested in knowing how to determine the capacity of my 2 - 6 volt batteries, connected in series. My batteries are about 2 years old and unfortunately, drained them down to zero use on a camping trip due to unexpected circumstances. I have a multimeter and can determine their voltage when charged fully. I can look on the label of the batteries and see what the battery capacity are based upon being new, but with their age and the incident described above, is there a way to best estimate their current capacity?

Next issue, is I would like to be able to watch a 55 watt TV while boon-docking and have purchased a 140 Watt Power Inverter which will allow me to convert AC to DC for this purpose. Prior to buying this inverter, my experience has been having 2-4 LED lights on in the camper, frig on propane, occasional use of overhead fan and the furnace on in the evening, plus using the water pump occasionally during the day and night with no TV. I have an 85 watt solar panel that restores my batteries on a daily basis, but this is determined by idiot lights in my camper or on the solar panel controller. I would like to have quantifiable data rather than idiot lights.

I just purchased a watt meter and power analyzer meter to be placed between my batteries and the solar panel controller. It will read the watts, and amps being delivered by the solar panel to my batteries and in turn show me the Volts of my batteries.

With the two measuring devices, multimeter and watt meter, how would you recommend that I first, quantify my batteries capacity, camper load for average day, and whether my solar panel is adequate to recharge my batteries on a daily basis. I am not an electrical knowledgeable person, in fact, a beginner and would like some suggestions on how to better quantify my system and better understand the batteries usage.

Thanks in advance if you have some suggestions!