Upgrading My RV Battery Bank and 12 Volt System

A Little of My Rigs Battery History

When we bought our 30 foot Keystone Cougar fifth wheel new it came with one preinstalled deep cycle battery rated at 85 ampere hours. Having camped for many years in a campervan with a similar sized coach battery, I knew that 85 AH capacity wasn’t going to cut it. We were headed off on a one-year journey and planned to do some off the grid dry camping (AKA – boondocking).

I decided to increase our battery capacity and purchase a pair of six-volt golf cart batteries rated at 225 AH. I installed them alongside the original 12-volt deep cycle battery and included a switch so I could use them as separate banks. Since then I’ve used the pair of 6-volt batteries as our main boondocking power source with the single 12-volt battery as a backup source.

Salton Sea State Rec Area California

This setup worked well for us and along with our Champion generator allowed us to enjoy beautiful off the grid locations for weeks at a time. We’ve really embraced boondocking so last winter I busted my solar power cherry and installed a 200-watt solar kit. It was an awesome addition to the rig cutting down our reliance on the generator a great deal.

While the 200 watts was sufficient for our power needs on bright sunny spring days it was still a little lacking when it was overcast or during those very short mid-winter days. Because of this I plan on adding two more 100 watt panels for this snowbird season bringing our total solar wattage to 400 watts. Before adding the extra solar, I’ve decided to first upgrade the battery bank with 4 fresh six-volt batteries with a total capacity of 464 AH.

Front storage bay - old battery setup and wiring

Front storage bay – old battery setup and wiring

As an RV battery bank upgrade, I’m removing the 2 old six-volt Trojans and single 12-volt battery and simplifying things into one 4 battery bank. I’ve chosen to go with Interstate GC2-XHD-UTL lead acid type batteries rated at 232 AH. I chose Interstates because they were in my price range, have dealer locations almost everywhere and I’ve had really good luck with that brand in my diesel truck.

Working with electricity and batteries can be dangerous! Performing these modifications may void your warranty and/or RV insurance. This article is for educational and entertainment purposes only and should not be taken as instructional. If you decide to do the same modifications as I’ve done then research and be aware of the risks involved. I accept no liability. You have been warned!

Installing 4 Six Volt Deep Cycle Batteries

First thing I needed was a way to contain the batteries with a storage box. I hit up a local marine supply store and found a plastic battery box (similar to this) sized to hold my 4 six volt batteries. It also fit perfectly in my Cougar’s front storage compartment.  I cut a hole in the bottom and lid to provide ventilation of battery gasses. My trailers front storage is already pretty well ventilated to the outside due to the front landing jack and propane tank openings, but I figure the more ventilation the better.

464 AH RV Battery Bank

Next I wired the four batteries together. I upgraded the original 4 gauge automotive battery cable to a thicker 1 gauge automotive starter cable. When wiring 4 six volt batteries together you want to series wire them in pairs to create two 12 volt batteries and then wire those in parallel.

It’s best to use the shortest amount of wire as required. The shortest pre-made 1 gauge wire I could find was 18 inches. It will do for now, but I plan to shorten them in the future. A serious boondocker buddy of mine and  has all the tools and bits and pieces to custom build the wires.


To hold my battery box in place, I added four eye bolts, two on each side of the box. I then use a pair of cargo tie down straps. To complete the battery storage box, I added rubber grommets in the cable feed holes. I then added dielectric grease to all the exposed metal connections to prevent corrison.

Hooking the New Battery Bank to the RV 12VDC System

My RV’s 12 VDC power system now has three main circuits fed by the batteries. There is the original main feed installed by the manufacturer which branches off and powers all the rigs 12-volt circuits like lighting, motors, water pump, fans and appliance low voltage circuits. Then there are two more circuits added by myself, the solar power input circuit, and the inverter output circuit.

12 Volt wiring

The main feed I have left just like the trailer manufacturer made it, except for installing a 12-volt power disconnect switch. Many RVs have this switch as standard equipment but no such luck with our Keystone Cougar.

1000 Watt Pure Sine Inverter Wiring

I’ve mounted my 1000 watt pure sine wave inverter close to my battery box to reduce the length of wire needed to power it. The further away the inverter is mounted the thicker the gauge of wire required. The larger the size of wire used the better, but it’s a trade-off between how much you can afford. By mounting the power inverter close to my battery bank, I was able to get away with using a smaller gauge cable.

Xantrex 806-1210 PROwatt 1000 SW Inverter
Price: $228.78
88 new from Too low to display3 used from $190.00

*Caution* – You don’t want to install an inverter in the same enclosure as the lead acid batteries. Battery fumes can cause corrosion to the inverters circuitry or a spark from the inverter could ignite the gasses.

In my particular install, the batteries live in their own ventilated box and the trailers front storage is also well ventilated. This allows me to safely mount my inverter fairly close to the batteries.

As an added measure of safety and convenience, I installed an 80 amp switchable circuit breaker between the battery bank and the inverter input connection.

12 volt RV battery and Solar System diagram

Solar Charge Controller Wiring

Last winter I installed a 200-watt solar power kit from a company called Renogy. It came with a simple 30 amp solar controller which transfers the energy from the solar panels into my battery bank. Again just like the inverter wiring, the shorter and larger gauge the wires are the better. I was able to mount my two 100 watt panels on the roof right above the front storage compartment and run the kits wiring almost straight down into it.

Renogy 200 Watt 12 Volt Eclipse Solar Premium Kit
Price: $694.99
You save: $25.00 (3 %)
1 new from $694.991 used from $492.00

I mounted the controller just a few feet away from the battery bank. From the solar controllers output feed into the battery bank I used a short and fairly heavy 4 gauge wire for maximum efficiency. The 4 GA wire is much thicker than really required for this small solar system, but I have plans to upgrade the solar by adding a few more panels in the near future.

For circuit protection, I added a 30 amp fuse on the input side of the solar controller and a 40 amp switchable breaker on the output side. This allows me to easily disconnect the two circuits if I need to do any repairs, upgrades or maintenance to the solar power system.

Video Detailing My RV Battery and 12 VDC Wiring

Conclusion and Future Upgrades

I’m really happy with the new battery bank and wiring setup. It’s a nice improvement over the complexity of the three mixed battery type arrangement I had in there before. I actually gained some more usable space in the front storage compartment. Weight wise I have added about 80 lbs.

I believe the steel front storage pan is plenty strong enough, but I will have to keep the additional weight in mind. Our one ton dually truck can handle it but I’m cautious when it comes to the trailers max GVWR.

Finished Battery Bank Installation

In the coming months as funds permit, I’m looking at installing several more items into my 12-volt power system. I plan to install a higher quality solar charge controller. Also, I would like a sophisticated battery power monitor that gives me information like the battery banks state of charge and the amount of power my solar system is providing.

For increased safety, I want to install a catastrophic failure fuse and the addition of a high-quality charger close to the battery bank. Likely an INTELI-Power 9200 series converter dedicated to using the generator for off-grid charging on those cloudy days. I’m not really impressed with the battery charging capabilities of the OEM charger. I’m pretty sure boondocking was not a top priority.

See more Love Your RV! Mods and Upgrades

RV Battery and 12 Volt Wiring System upgrades - Love Your RV! blog http://www.loveyourrv.com/ #RVMods #RVing

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  • Richard Messer

    Ray I am installing a Xantrex Freedom 2012 in a 36′ Damon MH. I will connect it to the current 2 Interstate 6v house batteries attached the the frame and under the entry steps. I want to add 2 more but in the adjacent compartment where the inverter is installed. However I am concerned with possible corrosion to the inverter. I liked the way you ventilated the battery box. Where can I find a similar box for 2 batteries? Great Blog!!

    • Thanks Richard,
      You might try this site – http://www.allbatterysalesandservice.com/browse.cfm/4,576.html
      or check out some local marine/boating supply places that’s where I found mine.

      • Richard Messer

        That looks like the perfect container for me Thanks! Xantrex does not recommend placing the inverter/charger in the same area as batteries. However, if the batteries are contained and vented such as yours I don’t think there should be a problem. What do you think? I can place them in another compartment and run my cables about a foot longer if I need to.

        • The smaller the wire run the better. I’ve never seen any corrosion on anything in my compartment so I’d say it works well at keeping the fumes contained. Is there a way for you to have a lower vent and a higher vent. On mine, the bottom has a hole to draw in fresh outside and the natural convection chimney effect as the batteries heat when charging moves the gases out. If not it might be a good idea to install a very low current fan.

        • Richard Messer

          Yes I can place a hole in the bottom and one in the top with a hose to vent out of the compartment. The compartment sits under the main floor and is a hard rubber/plastic with 1″ ribs across the bottom for support. I may have to beef it up a little to support the weight. I thought I saw in your video you placed the new box over an existing hole. My longest run from the inverter to my existing batteries is about 20″ to a 250 amp fuse mounted on the frame and 12″ to the positive side of the battery. The negative cable is slightly longer. When I add the 2 new batteries the cables will be slightly shorter.

        • Sounds good. Ya, I used the same hole in the compartment floor that the OEM battery used.

  • Jennifer B

    My plastic battery box arrived from Everett yesterday (exact one you recommended), within two days of ordering it… drove down to my mailbox in Blaine, WA, picked up my new Champion 3500watt remote start inverter generator (based on your love of your pair) and the plastic box and am loving life (moved into my RV up near Kamloops for the Summer months and then headed to the Southwest the end of Summer.. you’ve been a REAL motivator for many projects.. thanks again.. PS: I received an email that the levelling system you reviewed is on the way as well.. YAY. Next upgrade is a 9270 converter charger, want to stick with the standard ac plug so that’s as high as I can go. Did you just pull the fuse on the stock inverter so it doesn’t try to charge your batteries as well or how did you keep from getting loops in the system are you using an automatic transfer switch when on generator or just plugging into your jennie?

    • Cool, sounds like your getting things all set up nice! you can always just flip off the OEM converters breaker to prevent any looping.
      We don’t use a transfer switch as our power needs are pretty meager when boondocking. Here is our inverter setup – https://youtu.be/yV2xJiHSbfU

      • Jennifer B

        Thanks Ray….

  • Tom Kendall

    Hey Ray,
    So my solar install is complete. Thanks for all your feed back.
    Questions for you: At the breakers- do the incoming power go on the “Batt” terminal and the load go on the Aux. side for the Charge controller to battery and also battery to inverter?
    And if I were to plug in “shore” power to my PSW inverter how do I keep it from “looping” ( I read somewhere that that’s what its referred to) and draining my batteries? Do I just trip the breaker at the Inverter/Battery bank circuit?

    Again thanks for all your help, not sure how to post pics, it turned out pretty awesome if I may say so myself :o)


    • That’s awesome!
      I have a 40 amp breaker in the positive line between my charge controller and battery banks and 80 amp in the positive line between my inverter and my battery bank. The trailer came with a breaker in the positive line between the battery bank and the RV 12 volt loads. I’ve also recently installed a 200 amp catastrophic fuse very close to the positive battery output as a final failsafe .

      To keep the charging system from looping turn off the breaker for the RV’s charge converter. You’ll likely find the breaker inside on the main electrical panel.

      • Tom Kendall

        All is well so far…… I have the 40 amp as we’ll ( you helped me locate, thank you) and a 120 Amp at my Samlex PSI 2000W.
        So it looks like they have the charge converter and the fridge on the same breaker. I’m thinking I should put the fridge on its own breaker . Any thoughts, Pro or Con ?

        • I don’t think it will matter since the fridge will run on propane when off grid anyway so shouldn’t need the AC power to it.
          The fridges electric element draws 375 watts so you definitely don’t want to be using that as it takes very little propane to run. 🙂

  • Tom Kendall

    Good morning Ray,
    Thanks for your help on locating the 40 Amp breaker. All parts are on their way :o)
    You mentioned that you went with Interstate Batteries – GC2-XHD-UTL 232AH, due to your needs and budget.
    Where the batteries reconditioned or new?
    I called my local Interstate rep. and they have both available. New $173 ea, and Reconditioned for $55 ea.
    In addition I contacted the Battery Guy here in Tucson and they can deliver, yes deliver, 4 – New Trojan T- 105’s 225AH for $520. Not sure if they are T-105 RE or not.
    I would greatly appreciate your comments and feed back.

    Have a great day doing life!


    • They were new and I bought them right from Interstate’s own stores, figure they must be fresh and good warranty. 2 in the US at the store in Palm Springs they went for $124 each after getting $30 dollars off for the old battery. The other 2 I picked up in Canada for about the same cost in USD but I didn’t have old ones to trade in.
      That’s a great price for the Trojans and free delivery. Wow!

  • Tom Kendall

    Hi Ray,
    I was wondering where you found the 40Amp resettable breaker. I can locate them in AU but they do not ship to the US.
    Thanks for your help, and great posts for your mods. Im setting up to go solar and all parts are on their way except the 40 amp breaker.

    Enjoy your day doing life!


  • Duane Walker

    OK, thanks for the response…, that’s definitely encouraging!
    Our Cougar is currently in my shop as that’s where it lives during the off season.
    I’m still in the process of looking and figuring the best plan of attack to beef up the battery box for the 4 6 volt batteries.
    By the sounds of your experience, I may not need to be ‘quite’ as concerned as I was initially. Solar panels are one of the next projects after the batteries.
    I really enjoy watching your update videos, they’re very informative and helpful.
    Keep up the good work…!
    D. Walker

  • Duane Walker

    Hi Ray…
    I’m curious about the battery weight in the battery compartment. I’m wanting to also use 4, 6 volt golf car batteries but looking closely at the battery compt. on my cougar (mine is a 244 RLS but probably the same construction)… from what I can see, the rear and sides look reasonably strong being welded but the front looks very questionable.
    I’m wondering if you’ve seen any signs of a weight problem by now? I’m thinking of welding a 1.5″ x 1.5″ steel angle to the underneath side of the front edge of the steel floor and extending it over underneath the edge of the front portion of the lower body panel and then running some 2″ s/s screws up into the lower edge of that panel. I’m assuming it’s most likely OSB panel inside there as is most everything else.
    It just doesn’t look that strong to me the way it’s currently made.
    Looking at the rest of the construction of the trailer, I’m a bit concerned about that much weight up there..
    Any problems for you so far?

    Thanks much… D. walker

    • No, no signs of any problems after lots of miles and rough roads. I don’t carry many other heavy items in there, most heavy items other than batteries are in the truck box. I know quite a few people with 4 six volts in there and haven’t heard of any problems, but beefing it up is never a bad thing. 🙂

  • JZales

    Ray, another question I have is when mounting the panels on the roof are you fastening to the aluminum cross members or in between them. I assume you either have a diagram or a stud finder. Thanks again John

    • I don’t believe the roof has aluminium cross members, I think they are wood rafters with 3/8s plywood on top. I have no idea if I hit a rafter or not. There is no diagram. I drilled a small pilot hole first, then slowly tighten the large self-tapping wood screws provided with the panels, but not so much that the lost their bite. I had precoated each screw with sealant.
      Then I covered each bracket with lots of lap sealant. The panels are on their good, I can’t budge them. There are 8 screws per panel

  • JZales

    I learned a ton from watching your videos. Thanks. One question-on the schematic is there a negative lead that goes from the battery bank to the “12 volt circuits” ? I see the positive coming off the shut off switch but no negative.

    • Hi John, the 12 volts circuits negative lead is to the RV.s metal chassis like in a car.

  • djnott

    Thanks, you answered a big question I had, Ill stay with the extension cord for now as we’re not doing that much dry camping yet in our lives. But why can’t you plug into the shore inlet with adapters and be able to have 110 everywhere when you want it.

    • I can but then I have to remember to turn off the converter to prevent a charge feedback loop and make sure the water heater electric switch, AC and mIcrowave breakers are off and the fridge is in LP gas mode so I don’t drain my batteries real quick or potentially accidently overload the inverter.
      I find it simpler to just use the one AC outlet and a small extension cord in the rig if needed. Makes us aware of what we use knowing we are plugged into the dedicated inverter socket.

  • djnott

    I love how you did things, I’m following you example with my batterys. I’m not to the point of solar power yet but I do have an inverter hooked up. How did you get the 110 volts into the rv? My wife sleeps with a cpap at night so I run an extention cord up through a window for her to plug into.

    • Thanks. I bought the required length of armor-coated waterproof cable, then ran it inside the underbelly of the trailer along the path of the OEM wiring, then drilled a few holes in the basement storage area to have it come out below our entertainment center. I then wired in an AC outlet there and a plug on the other end for the inverter. – http://www.loveyourrv.com/1000w-pure-sine-wave-inverter/