Thinking I need some solar!

I really don't mean to belittle your friend, but there are all kinds of problems with his opinions and recommendations. As a frame of reference, our 43 foot motorhome has a large residential fridge, three entertainment centers, a 12 cup coffee-maker and a large convection microwave oven. All of them run off a 2800 watt inverter. A larger inverter - especially one rated at 5000 to 7000 watts would be way overkill - a waste of power and money.

It is technically possible to power a single roof air unit with batteries and an inverter, but very impractical. Our eight deep cycle AGM house-batteries (840 AH) and inverter could probably do it for 30 minutes or so on a full charge, but then they'd be drained. Do that several times and the batteries would be toast. We'd also be out of power for everything else.

The charging rate of our 960 watt solar array could probably keep up with the draw of a single roof AC unit for a couple of hours, but only if it was sunny. There's no way our relatively large battery-bank, inverter and solar array could power even two of our three roof AC units for any length of time. The surge from the compressors kicking on would overload the inverter. A larger inverter would require a proportional battery-bank - one that most RVs wouldn't have enough room for. You're talkin' a BIG battery-bank!

Powering an RV's roof AC unit(s) with batteries and an inverter just isn't practical - even with a relatively large solar array. If it were, people would be doing it all the time. A generator is really the only practical solution.

Kev

lions6 said:

Hello, I haven't been on here in quite a while. We just purchased a new 2017 Sundance 22 ft travel trailer. We are exploring the solar options. Has anyone sucessfully ran their A/C unit on an inverter with solar panels and batteries?  My friend is building his own teardrop trailer and he put a small residential a/c unit in it. He runs it off of a 5,000 watt inverter and a single deep cycle battery.  He keeps telling me that I should be able to run my whole trailer including the a/c on about a 5 - 7000 watt inverter with some solar panels to recharge the batteries. I currently have 2ea 12 volt deep cycle batteries on my new trailer and no solar. The last time we went boondocking we ran a generator 3200 watt with 4000 peak and it ran the ac just fine. However, I am not the guy who wants to run it all the time. In fact when I finally turned it off I could hear someone cheering from another campsite along the river that we had finally shut it off.  I would really like to know more about the solar option. I would be willing to spend up to 800 or 1000 bucks if I thought it would actually work but I don't know enough about it to make the jump just yet. I would really want it to be able to run the A/C as well as my dish network and 32" tv.  Can anyone tell me if this is even possible?    I know that my friends little trailer gets cool but it is only a few square feet since it is a teardrop trailer. It is easy for him to tell me I can do it but he can't even stand up or go to the bathroom in his trailer.  I just want help to know if it is actually possible.  Thanks, Mike  (lions6)

Click to expand...

Does your friend have any experience with RV air conditioners? All you have to do is run the math on usage and batteries, and you will confirm what Kevin says. Even your relatively small trailer is probably 5x the volume of a teardrop trailer.

A 14KwH Tesla Powerwall 2.0 battery ($5500 including inverter) would run a 15 amp roof air conditioner for about 8 hours before going dead flat. 

Then you'd have to generate 14+ KwH to recharge it.  Tesla conservatively suggests a 5 Kw solar panel array, though you could get by with less if you restrict your usage to sunny days or supplement the charging with a generator.  A 5 kw solar array is (50) 100 watt panels or (20) 250 watt panels, and so on.  Plus a suitable charge controller.

There's nothing that can't be solved by throwing enough money at it.  Except maybe finding enough real estate on the roof of the RV to hold the panels.  Maybe set up multiple layers of panels you can unfold to make a king size patio awning? 

https://www.energysage.com/solar/solar-energy-storage/tesla-powerwall-home-battery/

Or, you could tow something like this.  Of course, you'd have to leave the toad at home.

Variable speed Fantastic Vents or equivalent draw far less power then an A/C unit (1watt to 18watts depending on speed setting) and are a good alternative for cooling a rig when off the grid.  You could mount 1, 2, 3 of them in your roof as needed to keep the interior temperature down to about the ambient level.

All valid points. I know my friend only has to run his little window ac unit in his teardrop trailer for 5 minutes and the space inside his is like a meat locker. But I would rather have to run a generator and be able to stand up in my trailer than having to crawl into his. For him I know the inverter works but it is all due to the volume of the inside of the trailer and the very short amount of time it takes to cool it down. I was just really interested in seeing if anyone had done it without the generator. I really did think that it was impossible the way he was telling me to do it. And I certainly don't want to have to buy new batteries every few months due to discharging them so often using the inverter system since they cost so much. I will just run a generator and try to find places to camp where I am not around too many people or somewhere where everyone is using a generator. Thanks for all the input. I appreciate it. Mike

Here is how they did it.
https://www.youtube.com/watch?v=B0rZY5uotKI

A number years ago I purchased a 115 watt solar panel, back then it was around $500.00 and a solar TriStar Charge controller another ~$150.00  and replaced the house battery under the door  with three Costco RV type batteries.

Wired it all up and went boondocking for approx. 3 months in the Northwest Cascades.

My batteries could not be maintained using this  solar / battery setup and running the geny was sort of cumbersome as if the batteries fall below or near 50 percent capacity it can take quite a while to get them full again. If fall extremely low potentially it can take days to recharge to full capacity. Then problems starts all over again where the three batteries become low or depleted. Plus if you in the wilderness to enjoy wildlife and nature listening to a geny run all day so to run a few 12 volt or possibly AC appliances isn't really imo very appealing.

I eventually gave up on the solar / geny  and stopped using any electricity and the RV became more of shelter, i.e. a place to sleep.

For emergencies you should carry additional water, food, fuel, batteries, tools and at least a few supplies. Possibly a solar panel to charge small batteries.
_______________

From my experience boon docking in the Northwest my system should probably be a minimum 250 watt solar panels and at least twice or possibly more for battery storage.

I would need to try it again with an upgrade, such upgrade to 400 watt solar panels and a larger set of Trojan or possibly 6 volt golf cart batteries. However this can cost, be ready to spend at least $1500.00 for a new set of quality deep cycle batteries. The geny that came with the RV from the factory is a 4000 watt Onan, great generator however for only charging batteries I would prefer a quiet 1000 watt geny.

Or I could just keep it as it is and use the RV more as a shelter and forget about the electricity. Humans have lived a long time on this planet without electricity which hasn't historically  been around very long compared to other things humans rely upon.
_____

My RV using the RV furnace and all the appliances did not benefit at all with this solar setup and the geny  wasn't very good at keeping three RV batteries charged.

Things to consider in areas where there's not that much sunlight. Most RV furnaces are electricity hogs, mine runs a 7 amp fan that needs to turn on when starting, during operation and while stopping the RV furnace. LPG fumes need to be cleared when first starting and then stopping a RV furnace or the furnace won't operate.

I've since installed an additional Catalytic heater that doesn't require any electricity to run.

All the RV refrigerators I've looked at or owned require 12 volts to operate, when boondocking if you completely drain your batteries a RV refrigerator will stop working even though there's plenty of lpg.

RV refrigerators are normally are absorption refrigeration with a sealed network of tubes and chambers holding water, ammonia and hydrogen gas. A propane flame heats a chamber holding a solution of water and ammonia until the liquid boils. The ammonia gas rises to another chamber, the condenser, where it cools back into a liquid begins a cooling process.

This works great however absorption refrigerators are more expensive than an average home compressor frig and overall are usually more expensive to run as they require more energy for heat. Condenser motor refrigeration as you find in homes energywise usually cost less to run. Most of them now all have EPA energy ratings.Some people have tried switching over to an electric for when off-grid and boon docking however electricity is required to condense the  refrigerant so a compressor frig may not be the best option when boon docking unless you have a frig designed for off-grid, solar, renewable energies  using much less electricity.

We love our solar, have not had the generator out of truck in 2 years.... we do mostly boondocking.... BUT we have a 26' TT and I don't require a lot of extras when I am camping... No microwave, no AC, don't need that in Montana! ha.. but we did put on an 600 watt inverter in our new TT.  Spent 30 days in the RV,  I can charge my laptop, run the fan, and of course, we have a USB charge system built in our Cougar which charges all of our USB gizmo's.  We only have a 150 watts Go Power solar on roof with controller to maintain our 2 6 volt batteries.... biggest issue I read about on here is people want their coffee pots plugged in... So far we are fine with the percolator and may go to a large french press.... But then again I am low maintenance... and don't require hair dryer, etc.  figure we are clamping... with our King size bed and 32" TV. Now I have a new King Quest 4100 dome to put to the test this week on our solar and inverter... so we will see if I can run TV, receiver with our set up. I would be happy to just catch a program or two or news for a bit...  The only real advantage that I see with hookups is that you can guarantee you WON'T hear any generators!!!

Bill and Debbie said:

We don't do a lot of boon docking but recently had an experience that changes how I view being "off the grid"' We spent a total of 7 days without benefit of hookups. 5 of them were on the Rincon Parkway in Ventura, CA I had a little over a 1/2 tank of fuel but after 4 days I guess I had drawn the fuel down to 1/4 tank and the generator would not run. Had to stow everything away and drive off to get some fuel and return. We were running the genset about 3-4 hours a day. We have a residential fridge and did watch a little TV.

Would really like recommendations as to how much solar I might need to either eliminate the genset all together or drastically reduce its run time. I'm thinking a couple of roof mounted panels. Any thoughts would be appreciated.

Thanks

Click to expand...

Based on the information you've provided, it sounds like a solar panel system could be a great solution to help you become more self-sufficient and reduce your dependence on your generator. To determine the appropriate size of solar panels for your needs, we would recommend considering factors such as your energy usage, the size of your battery bank, and the amount of available space on your RV's roof for solar panels.

With a residential fridge and some TV use, it's likely that you would need at least a few solar panels to generate enough electricity to power your appliances and electronics. However, the exact number and size of panels will depend on your specific energy needs and the amount of sunlight you can expect in your location.

Bill and Debbie said:

We don't do a lot of boon docking but recently had an experience that changes how I view being "off the grid"' We spent a total of 7 days without benefit of hookups. 5 of them were on the Rincon Parkway in Ventura, CA I had a little over a 1/2 tank of fuel but after 4 days I guess I had drawn the fuel down to 1/4 tank and the generator would not run. Had to stow everything away and drive off to get some fuel and return. We were running the genset about 3-4 hours a day. We have a residential fridge and did watch a little TV.

Would really like recommendations as to how much solar I might need to either eliminate the genset all together or drastically reduce its run time. I'm thinking a couple of roof mounted panels. Any thoughts would be appreciated.

Thanks

Click to expand...

There are many variables to consider when designing solar, the most important is knowing your loads and how long they run for. like Kevin says, there is no one size fits all.. every situation is different.
I will give you an approximation of what you might need to power a residential fridge consuming 250 Watts at a 50% duty cycle. that value could be achieved in very hot weather.

to home in on a reasonable solution we need more data points such as

1. how much sun do you have ? sun insolation depends on location.
2. how long do you need to run the system when there is no sun ?
3. what time of the year are you using this system ?
and many more criteria.. LOL

for this example your location will be Colorado in the summer
and you require the fridge to run for 2 days without sun.
Colorado has approx 6 hours of peak insolation a day in summer.
and your daily total at 250@50% is going to be 250 x 24 x 50% = 3000 Watt/hours

Panel Watts = (Daily Watt Hours x 1.5) / Sun Hours
you will need 3000*1.5/6 = 750 Watts of panels.
Required minimum useable battery capacity = [2 days x Daily Watt Hours] / Battery Voltage
for a 12 V system this is approx. 2*3000/12 = 500 A/h
so that's a starting point for you..
if you need more info, pm me. i'll be glad to help out further.

if you would like to give it an economical try, thunderbolt magnum solar has a 100 watt solar kit for $189. harbour freight has been selling them and probably other geographical places do to.

i have one of my own. it works very well and saves generator time. eventually i plan to install a better system but figured once i do that, i will keep the thunderbolt as a portable when needed.

my highest amp production to my flooded batteries has been 4.8 amps. thought that was pretty good for a cheapie but was metered near the end of charging. the panels probably offered more but the batteries were not hungry enough.

the only thing its missing is an amp meter. i used my multi meter to get the 4.8 amp reading. cables are very long reaching and although you can attach all the panels together, they each have their own stand and can be kept separate. each panel is rated at 25 watt.

the kit also comes with 2 12 volt led lights and fixtures. very bright. i removed the guts out of one of my ceiling fluorescent fixtures and installed one of the supplied led bulbs. works very well and only draws .3 amps.

i am very happy with this product based on price, performance, ease of set up, and mobility. definitely a keeper once i get some permanent panels on the roof.