# Solar for RV



## plottrunner (Apr 3, 2008)

Does anyone on here have experience with RV Solar Panels? I am looking for something to just keep my batteries charged when I am not on the mountain. Sometimes it's 2 weeks or more before in between trips to the mountain and in that time, my refrigerator running on LP drains the batteries and stops working. I have to charge the system with my generator when I get there and by the time my fridge cools down again, it's time to go home. I was thinking about installing this setup and was wondering if I have to unhook it when I turn my generator on or when I plug into AC when hookups are available?

https://www.amazon.com/dp/B00F9EO5O...4AXEFW3Z2XBYJEQA0&ie=UTF8&qid=1500327698&sr=1


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## DallanC (Jan 13, 2009)

I've been interested in this too... you are on the right track, but going about it in the (slightly) wrong way.

First step is to figure out the current amperage draw, that then will dictate just what you need in the way of solar panels to replenish charge. IIRC, Fridge draws 5-6ah and the Propane detector draws a surprising amount and people forget about it. I assume all other things are powered down. 

So first get a cheap amp meter, and test the total draw in a rest state (make sure fridge is running ). Then you can start doing the math to figure out solar needs. Remember Solar only hits its peak output when exactly facing the sun, so you need to increase the size / amount of solar panels to assume an average charge rate during daylight hours, as well as account for cloudy days etc etc.

Once you know the drain, its each to compute how long the current batteries last. They should have a ah rating on them. 

Next remember the formula: Amps x Volts = Watts. With that you can figure out the wattage being used. 


So using "back of the napkin math": If your camper for example draws 20ah during a 24 hour day, you need 20ah x 12v = 240w. So you need to replace 240 watts of power loss daily to maintain current use. But, as panels only work during the day, you need to regen that during 12 hours or less. As panels have variable output depending on the angle between them and the sun, you need to account for times when they are less efficient (morning / evening). So while panels are rated at X wattage output, that is measured in a perfect scenario. In real world application, maybe the panels average 60% of max over a day, that means you would need to increase the overall output by an additional 40%, by adding additional panels.

Like I said, best place to start is to see what your draw is, then you can figure out from there what you need. The above example assumes keeping batteries charged at max, with X amount of daily drain. As you said, you might not care about that... just wanting to extend battery life from say, 7 days to 10.

From alot of RV threads I've read, people are running 300-400 watts of solar panels. In the long run its a helluva good thing to have solar panels mounted on the top of a trailer. In the short-term, you could also add a couple more batteries to last longer between trips down.

If you do choose something, I'd love to know what you get, and how well it works. 


Edit: Your amazon link shows that controller allowing the ability to add 2 more panels. So I think that kit would be fine, but you will need an additional panel or two once you figure out your amperage draw needs.


-DallanC


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## highcountryfever (Aug 24, 2009)

This is the solar kit I just purchased for my FIL:

https://www.amazon.com/dp/B00BFCNFRM/ref=nav_timeline_asin?_encoding=UTF8&psc=1

It is expandable up to 4 panels (400 watts total). While it is not the best components it should work for his needs and can be updated later as needed.


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## Critter (Mar 20, 2010)

My brother in law did this to his slide in camper years ago. The solar panel is around 3'x5' and sits flat on the roof of the camper. He put the controller in one of the side storage boxes and it works great on his two 6 volt golf cart batteries. He ran the wiring down through his bathroom vent. The only problem comes up if there is snow on the panels or heavy overcast for a couple of days. 

I would go down to a trailer store and talk to them about it. A lot of the newer trailers are coming straight from the factory with them. This doesn't mean that you need to buy from them but it will just give you the right information so you can go out onto the web to purchase them if you want.


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## klbzdad (Apr 3, 2012)

Do yourself a favor and get a MPPT controller kit and if you're charging 2 or more six volt deep cycle batteries, stick with Renogy and get this kit (below). Its the best money I've ever spent and my system is now a 400 watt system and I only run my generator early in the morning if I've been running the heater all night, to run a coffee maker and toaster at the same time or to run the microwave. Pays for itself in a year! Make sure you still exercise and equalize your batteries. Oh, and I installed a battery blanket in both as they hate cold weather!

https://www.amazon.com/Renogy-Monoc...id=1500336047&sr=8-1&keywords=renogy+mppt+kit


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## muddydogs (Oct 7, 2007)

I have the Windy Nation solar panel kit on my toy hauler. I went with 2 panels for 200 watts and there little bit better controler. here is a link showing the controller I have in there 100 watt kit. https://www.amazon.com/dp/B00JML23X0?psc=1

In the spring, summer and early fall I run my LED lights as much as a want, heater if it's cold at night and maybe the tv for a couple hours to let the grandkids watch a movie and have no problems keeping my batteries charged. During hunting season if it's cold I sometimes have to run the generator to top off the batteries as I just don't get enough sun to get a complete charge with the low sun angle and sometimes cloud cover. Other then that I never run my genny as I don't need to and I never plug my trailer into shore power when I get home since my panels take care of the batteries. I was planning on setting another 2 panels on my roof but I find the 2 panels due just fine most of the year and it's not worth the cost to add 2 more plus I need to run the genny a couple times a year anyway.

For installation I purchased extra cabling from WindyNation to make the run from the panels to the controller. For the controller to battery run I used a set of 4 gauge jumper cables and added my own cable lugs purchased from Windy Nation. I purchased a cheap crimper off Amazon to crimp the lugs.

I will say your batteries are probably done, the experts say not to draw a battery down past 50% which equates to about 12 volts, a time or two doesn't hurt the batteries to much but doing this a few times will weaken the batteries and they won't take or hold a charge as well. Sounds like you are running them down until there isn't enough power to run the fridge which is pretty low then your parasitic draws (co detector, propane detector, radio display, sometimes smoke alarm) are still pulling power which is probably dropping your batteries to nothing. I would plan on replacing batteries when doing solar to get its full benefit.

If you go this route hit me up for info on adjusting your controller for charge inputs so you don't boil the water off your batteries when you are not there. If your close to Ogden your welcome to borrow my crimper for your cable lugs.


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## plottrunner (Apr 3, 2008)

Thanks for the advice. I have cable lug crimpers and I do plan on replacing both of my 12 volt batteries. These batteries I am running are 3 years old anyways so they have been drawn down and recharged more times than I can count. I think I will just start with one panel to maintain and I will still use my generator as I draw more power than setting up an inverter will handle...


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## Loke (Sep 7, 2007)

I'm told by quite a few serious campers (they are out just about every weekend) that running two 6 volt batteries in series will give better battery life than two 12 volts in parallel. I plan on converting mine when I need to change them out. The ones that have solar panels are both running 80 watt panels, and only run their generators when they need air conditioning. I've been looking into a couple of 135 watt systems, still trying to decide if I want the permanently mounted or portable one.


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## sagebrush (Sep 8, 2007)

you will need any least 300w total to charge your batteries each panel will only put out 5-6 amps each. that is the same as having a trickle charger. it takes up to 12-15 amps to charge a battery during the day. if you do not charge a battery fully and keep using it day after day sooner or later you will deplete the charge in the battery. 
those marine starting batteries that are sold just about every where will not last very long being used this way. you need to get a deep cycle battery like the 6volts.
I have six 6 volt batteries on my trailer which are separated to get 12v in trailer and 110v at the same time without using the generator.

I have two different systems on my trailer one is 300w for the house batteries and 600w for the my 110v use. this way I stay away from the generator. you have to make sure that you park your trailer where it will get the most sun, during the day for the panels.

https://www.wholesalesolar.com/rv-marine this is a good place to start reading up on this, stay away from your trailer rv supply stores . buy most of your supplies on-line
when installing it go down thru the vent by the fridge.


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## plottrunner (Apr 3, 2008)

How big of an inverter do you use to get 110v sagebrush?


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## DallanC (Jan 13, 2009)

I run a 200watt inverter that powers our TV / Media player combo, works great, the TV draws well under that so its been problem free for 7 years now.

-DallanC


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## sagebrush (Sep 8, 2007)

its somewhere around 1500w depends on what you want to run with it. for me its tv (microwave 900w), toaster, and coffee pot . I try to keep things under 1000w this way it won't drain the battery to much the microwave is the biggest consumer . just don't run it except for heating up things, when in a hurry. I also have three outlets In the trailer for any electrical devises.


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## DallanC (Jan 13, 2009)

How big are the golf cart batteries vs say a deep cycle rv battery?

-DallanC


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## sagebrush (Sep 8, 2007)

In dimensions about the same. In amp hours most are 230 amp hours vs 80 for 12v


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## muddydogs (Oct 7, 2007)

plottrunner said:


> How big of an inverter do you use to get 110v sagebrush?


Any inverter will convert 12 volt to 110 volt, what you need to compare is watts. A 400 watt inverter won't run a 1000 watt toaster.


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## abellay (Nov 12, 2020)

Nice, that means you really found a good quality one, what s the brand?


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## avalon_star (Nov 12, 2020)

_I am just starting out my RV and I am not really good at the electrical part, watched a lot of youtube videos, but still not really a pro. This thread actually clarified a thing for me. But I also have no idea how to finish my RV. I called my father because he has some experience with electronics but he also is not very good at this and I don't wanna call a professional because the idea was that I will do it on my own because it's more fun. Fortunately, one of my friends that has a personal RV heard about my problem and he advised me to visit this site https://www.palmgear.com/best-rv-inverters/ and it helped me very much and I hope that it will help you too._


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## legacy (Sep 30, 2007)

Loke said:


> I'm told by quite a few serious campers (they are out just about every weekend) that running two 6 volt batteries in series will give better battery life than two 12 volts in parallel. I plan on converting mine when I need to change them out. The ones that have solar panels are both running 80 watt panels, and only run their generators when they need air conditioning. I've been looking into a couple of 135 watt systems, still trying to decide if I want the permanently mounted or portable one.


After going through a set of 12 volt batteries every 12 months in my toy hauler, I finally swapped them out for two 6 volt interstates. Best upgrade I've done so far.


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## Al Hansen (Sep 7, 2007)

This is a great thread. Im also thinking about a panel to just keep the batteries up when parked in storage for the season. I take the batteries out during the off season. Thanks guys.


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## DallanC (Jan 13, 2009)

I mounted 2, 100 watt panels this year on my trailer. It works great for charging up the batteries. I get around 9.4amps in peak sun, or around 150 watts.

There are things I would do differently. I replaced the PWM controller that came in the kit with a MPPT. The cheap PWM would sometimes fail to charge showing under voltage from panel... even though I could test it at 19.2v. This bit me in the butt one day when I noticed the batteries at 11.9v due to a cargo light having been left on... and the PWM wasnt charging.

The new MPPT absolutely rocks. Dead reliable, and I love the display I can run inside the coach to monitor everything. That said, 200 watts of solar is plenty to run all my 12v systems, including tv / media player (those use 40w combined)... but it wont come close to running a laptop etc.

If I could do it over, I could save myself $30-40 skipping the PWM controller and going straight for the MPPT. This is the MPPT I went with, I chose the 30amp version which lets me add another 200 watts down the road if needed.

https://www.amazon.com/gp/product/B0794Z6496/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Anywho, I'm happy to answer questions on it if anyone has any. I spent alot of time learning / researching solar this past year.

-DallanC


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