when I was building my trailer in the back of my mind was electrical, type of charging system I wanted off grid: battery size, type of battery, whether single battery or running 2 batteries paralle to supply the power for my 12v. gear & equipment. I knew I wanted off grid charging system: solar. I researched a good solar company & found Renogy (which I gave a few phone calls to) & read up on batteries how large & types are the best & would give me a reliable power source & use time.
The 12v. equipment & gear you decide to use will determine power consumption. As for me I run Engel MR40 40 qt. 12v. portable fridge freez which pulls average .7amps to 1.25 amp on fridge (runs on demand) depending on the time of the year. My Endless Breeze Fan on medium pulls 1.2 amp hour (run continuously @ night in the summer while sleeping). My Proplex H2000 tent furnace pulls 1.6 amps hour (runs on demand in the cold winter months @ night while sleeping), I have miscellaneous 12v. gear like my Zodi Hot Shower system that barely pulls any amps do to the short time it runs for showering. These figures of equipment usage is very important & will determine battery use, battery size & type of battery & type off grid charging system (solar).
Solar system I run is Renogy: 2 100 watt portable panels with branch connector, 5 ft 10 agw pigtail between both panels, 30 amp charge controller, 20ft of 10 agw cable & VMax 125 amp hour AGM battery. I like this set up because @ certain times of the year (seasons) I can run as many panels I need, example: in the winter I just run 1 100 watt portable panel were in the warmer months I run both 100 watt portable panels parallel "together. In the winter months & early spring I leave my Engel @ home & replace it with a 70 qt. K2 Roto-molded cooler. For this reason my frozen jugs & ice stays in the cooler longer for days upon days because of the ambient air temperature & the only 12v. gear I run is my tent furnace, my Zodi Shower system & charging a cell phone. I like the portable panels over a stationary panel for the reason I can move my panel\panels to follow the sun to get maximum sun exposure. Having 20ft. of 10 agw cable length to make this possible.
A 100 watt solar panel (good quality) will produce 30 amp hours per day "that's" on a good day. This also can vary during different times of day (over cast) different times of the year with less sun light available in winter months. Running my (2) 100 watt Renogy panels together in spring & summer early fall months parallel the voltage would remain the same but the amperage would increase. This is were my solar system shines. The key is to have more going back into the battery or batteries than you have going out. Much like how a accelerator pedal works on a vehicle. The more you give it the gas the more it uses gas.
It is important IMO that what ever 12v. gear you use & how much gear has the lowest power consumption use as possible to keep your battery life while camping & its life span altogether in good standing. The problem of these lower power use consuming 12v. gear & equipment the cost is more in price. This why it's important to know how low you can discharge your battery before you damage it by over use of its power capacity aka "discharge level" which is 50%. Anything beyond this will shorten your battery life span, not counting your run time on the battery while camping. Example my battery for my adventure trailer is a VMax Tank 125ah AGM battery, usable power is 62.5 amps.
You need a solar system large enough that is capable of putting more back into your battery vs. what you have going out. A single 100watt panel wont do if you run a 12v. fridg\freez & other 12v. gear in the warmer months because of ambient air temperature (warm to hotter temperatures) will cause the fridge to run more often which in this case uses more power & the power consumption will be higher amps per hour than listed on the low side of the owners manual. This also goes for the fact that late fall & winter months we have short day light times which your amps per day are less than 30 amps. Remember that fridge will need to run @ sleep hours too 24 hrs on demand much like your household fridges do. The average portable 12v. fridge will run anywhere between every 15 minutes on the low to normal side (cooler weather) to every 8 minutes or less on the high side (warmer weather) depending geographic's. This will use more power from the battery which will go into the lower side of the 50% discharged level if the solar system isn't large enough to supply the power for recharging the battery supplying a reserve to the battery for night time use while running the fridge during day light hours.
I find that some folks will be "under powered" in solar because they are trying to save money on a system. They will blame it on the solar system when in reality the facts are they did not purchase a efficient sizeable solar system to supply enough power to begin with. To run 12v. gear especially off grid disperse camping is to have enough off grid power to supply the battery for a full charge during sun light hours while to run the 12v. gear during the day time hours @ have enough reserve in the battery to supply night time hour use. Again, the reason for this is.............they do not want to spend the money for a proper sized high quality solar system that is efficient for the 12v. gear they are supporting.
The photo is when the wife & I are out late winter early spring dispersed camping using only one of our 100 watt panels. We never had our battery below 10% of the actual total amp hour rating while disperse camping.
