Solar Panels

Solar panels are definitely heavy. We have double panel suitcase set up and it's a load! But as for additional weight added to the trailer , I guess you just have to keep in mind the the allowable carrying capacity. But considering there are lots of rigs around with solar setups, it must be worth it to be able to be off to grid to do it. As with very thing there are tradeoffs. Will be interested in what you end up doing.

Solar panels aren't heavier than a person and if we can walk up there then panels are fine. I'm guessing your camper is normally parked longterm and your roof is constantly exposed to sunlight. If so, you can safely mount solar panels on your roof without weight concerns. Travelling is a different story.  If you travel I recommend using a portable, movable solar panel or panels so you always have the option of placing them in sunlight, which you cannot always do if they are permanently mounted on your roof and you are parked in the shade.

Solar panel type and location also depends on what you intend to do and what your expectations are. My ST312VIK has one 100W panel mounted on the roof; I have been testing what I can run off of it for the past month now. I also have two 12V batteries mounted. Now the trailer is parked in full sunlight for most of the day as any trees that block the panels are just starting to get leaves. What I have found is for a weekend outing I can run the 12V fridge set to the "off grid" setting on the temp control, I can also run the furnace and 12V blower fan provided I don't set the temperature too high causing the heater to cycle more, & a few lights inside. What I have noticed is that if you get a partially cloudy day, or something more strains the system the one 100W panel can't keep up and after a few days the batteries are discharging more than the panel can recharge.

My solution will be to get another 100W panel for the roof and two 100W panels for on the ground so I can better place them as 3rdfo5 stated. Basically I plan to run the two on the roof in series, the two on the ground in series, and the two sets in parallel. The important thing to remember is to keep all the panels the same watt and amp rating if possible. Do your research and you will quickly understand why. I am not an expert on this but from what others I know have experienced it makes sense. See link for explanation.

mowgli-adventures.com/wiring-solar-panels-in-series-vs-parallel/

B&N,

Fridge was empty and it was in the mid 60's-70's during the day with overnight dropping to mid 40's.

As for the two 12V vs. two 6V. more just a matter of one 12V came with the TT so I bought another to match. When we retire I will most likely also go with the Lithium, just right now with only one panel I felt the money will be better spent initially on more panels. Our goal is to be able to run all 12V systems, short microwave bursts, and short coffee maker burst off the solar and only use the generator for those days you just have to have A/C.

Family owns 10 acres of land in Southern Utah that is great for staying at when visiting many of the National parks in the area, including Northern Arizona. Only draw back is it is $60,000 away from the power grid until someone develops something closer. We can get propane delivered and water via a well but electricity isn't happening anytime soon.

Once things settle down financially after our move I will be developing the solar array for this TT, I will post what I did and how it worked.

I did alot of research on batteries. Especially 2 6 volts in series vs 2 12 volts in parallel. The general consensus is a good quality 6 volt battery will outlast a 12 volt battery. So in a best case scenario, 2 6 volt batteries "should" be a better setup.
However, 6 volt batteries are harder to find should one fail during a trip, whereas a 2 12 volt battery setup will still provide usage should one battery fail.
Also, electrically speaking, batteries almost never have the exact same specs as each other, even when brand new. This means that in a 2 6 volt battery setup, which are connected in series, the maximum charge level will only be that of the battery in worst condition.
In a 2 12 volt battery system, which are connected in parallel, both batteries will charge to their maximum level independent of each other.
I chose to go with 2 12 volt AGM group 27 marine (non starting type) batteries for best deep discharge ability and maximum amp hours.
As for solar panels, I started with one 150 watt panel and quickly learned it wasn't quite enough to keep up with my power draw so I added a 2nd identical panel for total of 300 watts.
In full sunlight they can charge my batteries at 14.0 volts and 20amps. They are not hard mounted on my rig, I place them out on the ground and keep them pointed directly at the sun for maximum efficiency.

Lithium batteries are excellent, but very expensive and also require a specialized charger. The standard charger/convertor in most RV's is not compatible and will need to be replaced at even more cost. I haven't researched if the tow vehicle can charge them properly so I can't comment on that. I looked at lithium during my research and decided to go with more traditional AGM type batteries that do not need a proprietary charger.

Some perspective on solar panels based on my experience and subsequent investigation may be helpful to some folks.

I recently got back from 9 days of dry camping with my STT272VRK. My travel trailer (TT) features a 12VDC refrigerator, two (2) 100W solar panels and one (1) 100Ahr LifePO4 lithium battery.

After about 28 hours at the campground without hookups my 100Ahr battery died. The 200Ws of solar panels were insufficient to keep up with the battery discharge rate and I was forced to run my generator twice a day (2 hours in the AM and 3 in the PM during the campground’s allowable hours of operation). Even with the generator, it was a bit of a losing battle.

My analysis: Other than the water pump, CO detector and judicious use of LED lights, the 800 lb gorilla in electrical use is the Furrion 12VDC refrigerator. Reviewing the specs, I found out that the frig was using about 3.5 amps per hour (3.5Ahr) in “Off-Grid” mode. That’s 84A per 24 hour day for just the frig; rounding up to 90A to take in all of the other loads, the 100Ahr battery lasting about 28 hours is about right.

Fortunately I had a my original 81Ahr flood battery that I brought along and was able to swap that in for the LiFePO4 battery. Running a 10A lithium battery charger while I had the generator running, it took 10 interrupted hours to fully recharge the 100Ahr battery.

What about the solar panels? The rule of thumb seems to be that a 100W panel is good for about 30 Amp-hours per day with direct sunlight. However, roof mounted solar panels lack the ability to be always directed to the sun, plus other factors like tree shade and clouds diminish the panel to about 75% efficiency (or less). So, 75% of 30Ahr is 22.5Ahr. Given that, my two (2) 100W panels produced roughly 45 Amps per day which is not nearly enough to replenish the 90A daily draw from the battery. [It’s kind of a joke that the “Solar Package” offered by TT manufacturers is for a single 100W panel.]

I intend on adding two more 100W panels to bring my recharge rate up to about 90Ahr to offset the approx. 90Ahr load on my 100Ahr battery. The TT shore line, powered by my generator, can augment the battery, but not by much. The TT convertor only provides about 3 to 5 amps of charging to the battery, basically a trickle charge.

I considered just adding a 2nd 100Ahr battery in series with the first instead of adding the solar panels. This would provide a longer operation time, essentially another 1.3 days, without needing to replenish the batteries with solar or a generator. We already know that the TT convertor is inadequate for recharging one battery, let alone two, in a timely manner. With the current array of two (2) 100W solar panels, the replenish rate of 45Ahr against a 90Ahr load would eventually draw down the pair of 100Ahr batteries well before a week of dry camping is over.

So, I’m sticking with the single 100Ahr LiFePO4 battery and upgrading the solar array to four (4) 100W panels and see how that works out.