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!

[Padgett]

Good questions. I usually figure the watts of solar should be about equal to the AH of the battery(s) being charged. I have two 200AH 6v GC2s and 200W of solar panels.

When camping I usually see a full power restoration before noon on a bright Florida day.

After noon this time of year It often clouds up/rains.

If that 55W for the TW from the back panel or did you measure it ? I have a 32"(class) Hitachi that says 60W on the back and actually pulls 33-34W (measured) in practice (volume and brightness at normal levels).

But what I would suggest is to create an energy budget (spreadsheet) of what you may use and for how long (e.g. takes my Keurig 3 minutes at 64A of 12v to make a cuppa. This takes 24 minutes of bright solar to recover. Then determine what you need to either recover each day or reach the end of your trip before discharge below usability (50% of capacity is a good guesstimate for a true deep cycle battery, only 30% for an automobile battery is better)

[rbkinder]

Thank you!

[rbkinder]

The 55 watts is on the back of the TV. How did you measure your TV's watts?

[Padgett]

Kill-A-Watt (https://www.amazon.com/gp/product/B00009MDBU/) (best for measuring ma) or can use an extension cord split into individual conductors and a clamp meter (what I use to measure AirCond currents)

[scrubjaysnest]

To check the status of your batteries, fully charge them per manufaturers specs.
Let rest with no load for about 6 hours then check the specific gravity and compare to manufacturers specs.