The task of adding a solar charging system to your RV can be daunting to say the least. So daunting in fact that many RV’ers delegate the task out to the professionals. There are pros and cons to having someone else do your system. Just realize that if you have someone else do your system you are giving up control. It’s exactly the same as having, say, an addition put on a stick and brick house. You hire a builder/architect to do the design, they get your approval, then they subcontract out the work to the laborer who hopefully follows the plan usually using the cheapest materials possible to maximize the profit of the builder/architect. I’m generalizing of course and there are several solar companies where the builder/architect is also the implementor. Most of the time they will still try to sell you on whatever products they think are the best and will make the most profit. I’m not saying this is a bad thing, I’m just saying it’s the way it is. And, to be fair, I’m sure many of these companies are very good at what they do. A couple of those I’ve heard that are very good include AM Solar in Oregon and Northern Arizona Wind and Sun in Flagstaff, AZ although Wind and Sun won’t do the actual implementation of your system. Then there is a guy named Handy Bob, who is very knowledgeable in solar. He’s been building a shop in Montana.
I like to do things myself when I feel I can. Not just because I like to be in control of the process and materials but because I like to learn new things. Here is a list of pros and cons of doing a project like this yourself:
1. Control of the entire process: research, design, build, test, and implementation
2. Control of the materials used
3. Your education/learning and knowledge of the entire system is greatly enhanced
4. Challenge of figuring out the problems – if you like challenges
5. Work is done on your timeframe
6. Work is done in location(s) of your choosing
7. Cost savings in materials (usually) and labor
8. It was fun
1. It took longer to have the system implemented
2. Physically it was a challenge (those batteries were very heavy)
3. I was scarred as hell I would screw up
4. If you are tool challenged or don’t have any tools you will have to get over it and buy/borrow some tools
I really can’t think of that many cons to doing your own system. Even if you have issues with heights (being up on your roof) you can always break your system into stages and hire someone to do the roof part of the project.
Sometimes I’m a details type person and sometimes I’m not. Yes, it drives me crazy too. If you want more detail on something I just skim over, then send me an email and I’ll try to expound. In any case, the following is what I did to implement 960 watts of solar panels charging four 300 amp 6-volt batteries.
The very first thing I did was spend many hours researching and reading on the internet. Today there are all kinds of forums, companies and individual websites that provide a plethora of information about how to put in your own solar charging system and what products work best. The three main areas that I researched and had to make decisions on were: what type and size batteries, what inverter/charger and what size and how many solar panels. Then there were the minor areas: what size solar controller, wires, fuses and breakers.
My RV has three electrical systems as I believe most do. An AC, a DC internal and a DC external system. I’m not going to go into too much detail here about the differences between AC and DC but the AC system in my RV is all of my outlets (inside and out), the air conditioner/heat pump, the electric half of the hot water heater, the electric half of the refrigerator, built in vacuum, ceiling fan and some of my incandescent lights. The AC system components work when your RV is plugged into shore power (the campground pedestal). My DC internal system consists of those components that work when I am not plugged into shore power. The DC internal system uses the energy from your batteries only and consists of a few incandescent lights, all of my fluorescent lights, water pump, the gas furnace fan, the external security lights, front jacks, rear stabilizers and the power to move the glides in and out. Finally the DC external system is used by your RV (trailer or in my case 5th wheel) when you are plugged into your tow vehicle. The tow vehicle batteries/alternator provide the energy to power your RV external driving lights like blinkers and stop lights and to actuate your trailer brakes whether electric or hydraulic. For the solar project I did nothing to change or interfere with the DC external system – at least as far as I know.
Backing up a bit it’s important to understand how your RV batteries (whatever voltage, size or number) get their energy when you don’t have a solar charging system. When you are plugged into AC shore power I told you before that it powers all of the outlets. One of the outlets in my RV is used to plug in a “Converter”. The “Converter” was next to my batteries (I had two 12-volt Interstate batteries) and was used to charge my batteries. It was a fairly small black box that always hummed and was always hot. It continually charged the batteries while the RV was plugged into shore power. I had a “Magnetek” converter which I’ve read is very common in RV’s. It’s not very efficient but it keeps the batteries charged.
After doing a ton of research and reading, it was time to take action. I made a list of everything that used electricity in the RV (both AC and DC). Then to the right of the listed item I put: how many, what it’s maximum wattage was, a guess at how much time that item would be used in a day (hours or minutes), and a total wattage used figure. I added up the total wattage used column to give me an approximate wattage used per day. For the most part I was generous about the usage. I felt it was better to overestimate rather than under. For example, we have one toaster rated at 750 watts. I figured it would be used 5 minutes per day which is a total of 62.5 watts per day. Some days we use it more but most days we don’t use it at all. I did this process for everything and I came up with a total of about 5000 watts. I then divided this number by 12 volts. I decided to stay with a 12 volt battery system only because that is what I had in the RV even though I could have gone with a 24 volt system. So, dividing 5000 by 12 gave me 418. 418 is the approximate number of Amp Hours I would use per day if I used everything on my energy list for the assumed length of time. Here is the energy equation: Watts = Volts x Amps. The reason you need to know the approximate Amp Hours (AH) you will use per day is because that it how the batteries store and disperse energy – via Amp Hours. Or, at least it’s the easiest for you to measure how much energy your batteries have and what the batteries can store when you determine which batteries to buy.
418 Amp Hours. That’s a huge number per day but it’s not realistic. First – rarely do we use all the items on the list every day. Second, the amount of time we use them might be less than estimated. Third, we can learn to practice conservation when we need to.
Batteries. I went back and forth with what kind of batteries to get. My existing two 12-volt Interstate batteries were not going to cut it. They stored about 80 AH’s each for a total of 160 AH’s. Before I go on there are a couple more things you should know. Batteries last the longest when they are not drawn down less than 50% of their total AH storage capacity per charging cycle. I will assume a daily charge cycle. So, a 100 AH battery should only be drawn down 50 Amps per day. The less it’s drawn down per charge cycle the longer the battery life. Second, some of the batteries Amp Hours will be lost due to battery inefficiency and seeping voltage in the wires. Third, batteries need to be charged correctly in order to reach their maximum charge (maximum amp hours they can hold). Last, batteries, over time, become less efficient. Think – cell phone battery or laptop battery and how after a few months or a year it says it’s fully charged but it seems to run out of juice much faster. Sucks, doesn’t it?
This is how I decided after doing the research: Based on experience from others, I went with four 6-volt batteries even though I could have gone with 12-volt batteries. I felt the 6-volts would last a year or two longer than 12-volt batteries. It probably doesn’t make any difference but more off-grid RV’ers have had success with 6-volt batteries so that’s what I based my decision on. Now, I had to connect the four batteries together in a way to produce 12 volts but I will talk about that later. Now, back to the 418 AH I might use per day. For 418 AH I would need to have over 800 AH capacity (shouldn’t bring below 50% capacity). That’s a very large battery bank not to mention a lot of added RV weight. So, I reduced what I thought was maximum usage (418 AH) by about 25% to 300 AH. This is how I got to four 6-volt 300 AH batteries. Four x 300 AH’s? That makes 1200 AH’s I know. Remember how I told you above that I would have to get the 6-volt batteries to produce 12 volts? Now is that time. You have to connect the four batteries to work in 2-pair. Each pair works as 12-volts. Unfortunately even though the volts go up, the AH’s stay the same. This means that two batteries working as a pair only store 300 AH’s of energy. Put the two pair together and you get a total of 600 AH,s. Then, you should try to never draw them down less than 50% so that really means you only have 300 AH’s to use! Finally, many batteries are rated for maximum AH’s based on 20 hours – not a 24 hour day. Why, I don’t know. The batteries I chose were on a 20 AH day so really I had less than 300 AH’s of storage. I could see we were going to be going the conservation route.
So, four 6-volt 300 AH capacity batteries. My final decision was what type of batteries. I am talking deep-cycle batteries here, not car batteries. Now I had to think about where to put four batteries. My existing battery compartment was near the front of the RV on the drivers side and held the two 12-volt Interstates. It didn’t have any more room. The Interstates are lead acid batteries which require distilled water added every so often. The compartment also needed to be vented because of the gases lead acid batteries can produce. If I was going to have four lead acid batteries I was going to need to build another sealed compartment that is vented or enlarge the existing one some how. Four batteries would be much heavier and I was worried about adding more weight to one side of the RV. I decided to build a new battery compartment in the front basement area. This is the area that is directly behind the truck and the lowest basement area of the RV (closest to the ground).
How was I going to build a sealed container for the batteries and still be able to reach in and add water when needed?. I researched automatic battery watering systems and they seemed a great idea. I saw how some people bought coolers or large plastic storage containers and placed the batteries in them to keep them sealed. Then they cut a hole in the compartment wall to run a venting pipe to the outside. It all just seemed like a lot of work and it would look messy. I couldn’t use the cooler or container idea because they would fit through the compartment door in the first place never mind trying to get the batteries into the container.
My other choice to lead acid batteries was sealed batteries – the AGM type not the Gel. These don’t need to be vented and don’t need to be watered. This resolved two of my major issues. But, they had two of their own issues. The first was not a big deal – they were a bit heavier than the lead acid. The second was a big deal. They were way more expensive. Like – twice the price. Well, I spent the money and so far it is way worth the added expense. I bought four Lifeline AGM sealed batteries – GPL-6CT to be exact. Since they are 90 lbs each I had to reinforce that basement compartment. I used a piece of exterior grade 3/4 inch plywood and drilled hole through it and through the basement floor which was exposed to the road. I bolted it down with galvanized bolts, lock washers and nuts. I countersunk the bolt heads in the plywood to keep the floor nice and smooth. I sprayed the plywood with varathane to keep it from absorbing moisture quickly. Then I used that spray insulation foam all around to edges to really give it a solid setting.
The cost of the batteries included shipping. I ordered them online from Powerstridebattery.com. It was worth it due to their weight of 90 lbs each. They arrived via an independent freight truck company in about a week. They delivered them on a palette and the driver fork lifted the palette right in front of my RV basement compartment. Perfect delivery! Since I knew the exact dimensions of the batteries before they arrived (online info) I was able to cut some plywood strips to keep the batteries secure and spaced an inch apart. Even though I saw other examples of putting the batteries completely together, I thought it would be better if they had at least an inch on all sides for breathing room. Finally I screwed two pieces of L shaped aluminum (easily drilled through) to secure them from moving anywhere.
My next expensive decision was the size and type of inverter/charger to purchase. First I’ll talk about the charger part of the inverter/charger. Remember the “Converter” I talked about above? That converter is really just a dumb charger and doesn’t do a very good job. When you are plugged into shore power essentially it just keeps the batteries so they stay at a certain voltage never letting them cycle down much but also never charging them fully so they never have their true AH potential. Not so good for any type of battery but safe and problem free for the RV manufacturer. They don’t care if your batteries don’t last very long.
The charger portion of a good inverter/charger will do a better job of keeping your batteries charged so they will last longer. The charger will have different stages and will be able to vary the voltage at each stage as the batteries get closer to being fully charged. You don’t want to fry your batteries (that’s why the cheap “Converters” play it safe with lower voltage). The charger portion of a good inverter/charger will also be able to do it based on the temperature of your batteries. Yes, temperature matters. Batteries don’t work as well in cold temps so a smart charger will know to up the voltage when charging cold batteries.
Now for the cool stuff. The “Inverter” portion of a good inverter/charger takes the stored energy from your nifty new batteries which is stored as DC energy and changes that energy to AC energy in order to provide power to all those outlets (or chosen outlets) in your RV. It will also power any AC lights or fans or whatever, if you want it to. How much AC energy produced at a given time is dependent on the size of the inverter you purchase. How much energy produced for a period of time is dependent on the size of the inverter and the battery storage capacity.
My decision of which inverter/charger to purchase was influenced by Jack Mayer. In fact I used his knowledge and experience extensively. Definitely visit his website and read everything you can in the “electrical/solar” section. It will help you make decisions on your system. www.jackdanmayer.com I went with a Magnum MS2812 and it has worked flawlessly. I went with the MS2812 because I found it at a great price on Amazon for $1500. It was not a refurbished model. I don’t have a problem with refurbished. I tend to think that refurbished items may work even better and longer than new ones because they have had the kinks worked out and have been more scrutinized etc. Your choice. I just know that $1500 was a good price refurbished or not. I wanted a bit more than a 2000 watt inverter because I knew we would be running the microwave which has a huge initial draw of voltage. I didn’t want to have to always turn everything else off before turning on the microwave. It has worked out extremely well. It’s a sine-wave inverter (cleaner AC voltage so to speak) and the charger portion is much more sophisticated than a plain “Converter”.
With these two components to the system (the batteries and the inverter/charger), I figured I should be able to remove my old batteries and disconnect the old converter and yang them out of the RV. Unfortunately not so fast. I needed to be able to connect the batteries to each other, the inverter/charger and the existing DC internal system. I needed new wires and the wires needed lugs. Lugs are the hooks on the end of a wire that slip over a battery terminal or a bolt. Think of the wires that attach to your car battery and think of the loop that slips over the battery terminal. That’s a lug. Again, more research. Information found: Size and length do matter! I knew it all the time. But, in the case of battery to battery connectors and battery to inverter/charger connectors you want to keep the wires as short as possible and as thick as possible.
I used 4/0 or “4 aught” welding wire for battery and inverter/charger connections. I also kept everything as close as possible. I measured the distance and number of wires to get an idea of how much wire to order. Then I counted the number of lugs I needed. I ordered the correct length of 4/0 wire from www.weldingsupply.com. I also purchased some 2/0 wire that I knew I would need to connect whatever solar charge controller I bought and also some 2 AWG wire that would run from the roof down to the solar charge controller. And last in my order to www.weldingsupply.com I ordered a pair of wire cutters (B-52 Barracuda Cable Cutters) I needed to cut the thick 4/0 wire.
From www.allbatterysalesandservice.com I ordered lugs for the 4/0 wire and for the 2/0 wire. I also ordered a heavy duty hammer crimper and finally some heavy duty shrink wrap.
I loved making the cables. After the batteries and inverter/charger were in place I measured the distance I needed and made one cable at a time. I took my time and measured carefully especially for the 4/0 wire which is stiff. The biggest advantage (other than cost savings) to making your own cables is being able to set the lugs in the correct position before you hammer crimp. Doing the shrink wrap on the cables was easy. I cut a two inch piece of heat wrap for each end of the cable and brought them inside and used the gas stove top to heat them up. I kept setting off the smoke detector if I let it heat up too much – but no big deal. The shrink wrap came out perfect.
I’ve decided I’ve gone into way too much detail here (Nancy thinks so too) so let me just list the final components I used and give a brief description. Then I will just post a bunch of pictures so you can see the result
MorningStar TS-MPPT-60 Tristar 60 Amp MPPT Charge Controller with Remote Temperature Sensor. This is needed to control the amount of voltage provided to the batteries from the solar panels.
Four (4) Trina Solar 240 Watt Solar Panels
Roof C-Box: Inside this box is where the bare MC wire ends connect to the 2/AWG wires that come down the stack pipe and connect to the solar charge controller (the positive wire goes thru the baby box breaker (40 Amp)
Three (3) MC Wires of varying lengths with interlocking connectors: These are used to connect the 4 solar panels in parallel/series to the Roof C-Box
Midnight Solar Baby Breaker Box with 2 DC Breakers (40 and 63 Amp)
400 Amp T-Fuse Block Assembly (Magnum): This fuse is on the positive wire between the Inverter/Charger and the Batteries
Bogart Industries Trimetric TM-2025-RV remote meter: This comes with a 500Amp Shunt that goes as close to the negative battery terminal as possible. This meter is acts as your gas gauge for the batteries. It shows you the battery voltage as well as the Amps going in (charging) or going out (using) as well as a calculated percent of energy (I like to use Amps) left in your batteries.
Magnum Inverter/Charger remote meter: This meter lets you turn on/off your inverter and your charger.
TriStar TS-RM-2 remote meter: Shows me the number of watts/amps being utilized to charge the batteries from the solar panels.
I mounted all the meters inside near my thermostat and fantastic fan meters for easy viewing from the main living space.
I put the two breakers in the Baby Breaker Box so I could isolate the TriStar charge controller. The Baby Box was mounted next to the charge controller. The pictures tell the rest of the story. Let me know if you have any questions. The system is working beyond my expectations. It’s been nearly two months since we implemented and I don’t think we’ve been down lower than 75% of battery capacity on any day. The panels are charging sometimes up to 150 watts even during heavy rain – just amazing.
The four panels and Roof C-Box (black box).
Here you can see the charge controller on the left, the Magnum inverter/charger and below it the Baby Breaker Box. The batteries are to the far right.
I also added a sub-panel in our bedroom closet directly behind the exterior Main panel. I pulled the main panel wires out that go to all the AC outlets and AC lights. I fed them into the sub-panel. I added two 30 Amp breakers in the main panel and fed wires to the inverter/charger and back to the sub-panel. Adding a sub-panel is definitely the way to go so you never run the risk of accidentally running your Air Conditioner and draining your batteries.
Here you can see where I added the 400 Amp T-Fuse (cover with yellow triangle) and over to the right just above the batteries is the 500 Amp Shunt for the Trimetric meter.
Here is the bracket I created and used to mount the panels to my roof. I designed them so I can manually tilt the panels if I desired. I used aluminum L brackets purchased at Home Depot. They have worked like a charm.