Mod #1: 6-Volt Battery Upgrade

Mod #1: 6-Volt Battery Upgrade

Submitted on: 06/05/08

     Category: electrical
Mod Rating: 12345

(95 ratings)

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Mod Description:

The most popular and perhaps the most controversial mod is the 6-volt golf cart battery upgrade. There has long been a debate within the RV community over what the “right” kind of battery you should choose when upgrading from the “standard” dealer-supplied 12-volt battery. Generally speaking, most RVs come with either 1 or 2 12-volt “deep cycle marine” type batteries. While these batteries are fine for general use, their performance tends to degrade quickly when deeply discharged frequently, drastically shortening their lives.

Mod Difficulty: EasySomewhat EasyModerateSomewhat ChallengingChallenging

To compound the issue, most RV charging systems (part of which is referred to as the converter/charger) are inadequate for recharging batteries in a reasonable amount of time. If you dry-camp (no hookups) a lot, you probably have experienced that your single 12-volt battery lasts for only 1 or possibly 2 days even with frugal use of lights, heater, water pump, fans, etc. Without electrical hookups, your battery cannot be recharged unless you have a generator or solar power. And even then, you must run the generator for a long time before bringing the battery up to a state of charge adequate for the next cycle of use.

Enter the 6-volt battery. While not a panacea for your battery woes, upgrading from a single 12-volt deep cycle marine type battery to a pair of 6-volt golf cart batteries (you need 2 to make 12 volts) can make your dry-camping time last quite a bit longer between recharges. Comparing a 6-volt battery to a “standard” 12-volt battery, you will find that the 6-volt golf cart battery will have much thicker lead plates inside, as well as more electrolyte (battery acid) capacity. These batteries can take much more abuse, i.e., deep discharges, and provide much more capacity, durability, and longer life. You still have the issue of recharging time but you might not have to perform a single recharge over a typical weekend of 12-volt power usage.

This mod is pretty straightforward. If you have a towable RV, like a travel trailer or tent trailer, your battery is likely located on the tongue of the trailer. Since a 6-volt golf cart battery has the same footprint as the “standard” 12-volt battery (they are an inch or so taller though), there is generally enough room on the tongue to accommodate 2 6-volt batteries. However, since they are taller, you will need to replace the battery box with 2 specifically made for 6-volt batteries. Simply remove the 12-volt battery, and replace with the 2 6-volt batteries, placing them either end-to-end or side-by-side. Carefully wire them according to the image shown above.

5th wheels will likely have the battery located in the front compartment in a sealed box that is vented to the outside via a hose. This presents somewhat of a problem in that the sealed and vented battery box used for the 12-volt battery will not fit a 6-volt golf cart battery. Your options are to buy a purpose-built box that can accommodate 2 (or more) 6-volt batteries, or fabricate your own box, being careful to ensure that the box is sealed and vented in the same way as the original box. Wiring is the same as described above.

Most motorhomes generally will have 2 12-volt “standard” batteries. However, there are a multitude of factory and dealer options for some of the higher-end models, with some having up to 8 6-volt golf cart batteries. You can still benefit from 6-volt batteries however if your motorhome has 12-volt batteries for the reasons already discussed. Some motorhomes, like class C’s, will have the batteries under the steps in the side entrance way, and might not be able to accommodate the taller 6-volt batteries. If this is the case, you will have to relocate the batteries. Alternative locations are the engine compartment behind the front bumper, a side door compartment (vented of course), or in a custom-built rack under the motorhome.

ModMyRV recommends these parts for this mod:

Trojan 6-volt Golf Cart Batteries
Sams Club - they really do carry golf cart batteries - cheap too!
Interstate Batteries Golf Cart Batteries

Battery Boxes
Allied Battery Golf Cart Battery Boxes
Blue Seas Twin Golf Cart battery Box

General Reference
Wikipedia Entry for Lead Acid Battery

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34 Comments For This Mod

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  1. cccale

    i have 2 x 12v deep cycle batteries with a 3 stage charger. Are there any special considerations in regards to the charger when upgrading to 2 x 6v batteries?

  2. ModMyRV

    Your charger size requirements will depend on the capacity of the 6-volt batteries you decide to install. 2 Trojan T-105s will get along well with a 60 amp 3-stage charger. Chargers providing less current will still work but will of course take longer to complete a charge. If you decide to install larger capacity (or more) batteries like the Trojan L-16, then you will need a larger charger, like an 80 or 100 amp. If you do upgrade chargers, be sure to also upgrade your charger wiring all the way to the battery bank to ensure the least amount of voltage drop and maximum charging current.

  3. jmt

    How would I determine if I needed 2 or 4 batteries. (Based on dry camping and hours of use)

  4. ModMyRV

    It would depend on how much capacity you want. The minimum would be 2 wired in series to make 12 volts, since your RV requires 12 volts to operate DC circuits. Think of electricity like water. If you were traveling through the desert, you would want to bring the most water possible that you could carry. This is your battery capacity. The less water you can carry, the shorter your desert journey can be. So if you want to use a lot of lights and run an inverter, then you need a lot of water.

  5. Jim

    A source that seems authoritative would say that your diagrams for interconnecting batteries are completely wrong especially for the 12 volt, 4 battery, setup.


    Their conclusion is that hooking 4 12 volt batteries up the way shown here, if you have a 100 amp load on your battery bank would result in as follows.

    The top battery provides 35.9 amps of the 100 amps.
    The next battery down provides 26.2 amps.
    The next battery down provides 20.4 amps.
    The bottom battery provides 17.8 amps.

    Seems crazy but they have a lengthy discussion about it and suggestions for improvement.

  6. Trailblazer

    When I did this mod, I had to come up with a solution for a battery box that was tall enough to hole the 6 volt batteries. What I did was take to more regular group 24 battery boxes. I cut the bottom our of both the these battery boxes and then slide them into the the existing battery boxes. I then used silicone to seal the the battery box insert to the existing battery box. You can see my set up at:

  7. kraythe

    I wonder how many batteries you could add without problems to a travel trailer. What if I wanted to put in 6 batteries instead? Would I need to worry about venting the box? Can the batteries be stacked on top of each other?

  8. A9

    Installing the batteries is great. Do you have a source for battery boxes to mount the batteries to the frame rails of a Class C type RV?


  9. ModMyRV

    @A9 - How are your batteries mounted now and what kind are they? Are you looking to upgrade and if so what kind of batteries and how many?

    Often in a Class C, the battery mounts need to be custom built. A second option is to give up a storage compartment and build a battery compartment out of that. I did this on the Super C Endura I had a few years back. I left the original batteries in tact that were just next to a compartment but only accessible from under the coach. I mounted 2 more batteries in the adjacent compartment and wired them through the wall of the compartment using an A+B switch. Worked out really well and I didn’t have to do any welding and very little fabrication.

  10. gafftaper

    Just finished this mod. It was relatively easy because my travel trailer already had two 12 volt batteries on the tongue. Just replaced the battery boxes with 6 volt sized and I was good to go.

    While I was at it I decided to upgrade to a new higher power converter. That took some time as I had to run additional wire to the battery to account for the additional power. But I’m looking forward to some serious power and a quick recharge.

  11. imacrichie

    i have a question i have 2 12v batterys. I also bought a small battery charger. was wondering when i go to charge batterys (charger connected to generator) will i need to disconnect cables to trailer to keep from burning anything up inside ?

  12. ON-A-ROAD

    What kind of trailer do you have? Was wondering because most have a converter/charger. If your hooked to shore power it should charge your batteries. If you do have one and want to charge them off a outside charger, I was told it shouldn’t hurt anything. I asked the same question on another site. You will want to connect to the + to the battery first, then the ground to the body some where. Then start the genny. (I was told this too, as one spark after charging can = an explosion). When it’s done charging, unplug the charger, before removing the clamps.

    I would not plug into shore power just in case you do have a converter/charger, while charging your batteries from a generator.

  13. Webb White

    How can you determine if you have a dead cell in a T-125 Trojan battery? Do those battery rejuvenators work?

  14. Art Martinez

    The wiring diagrams for the multiple batteries (at the bottom of the set of pictures) is NOT correct for the 12v wiring diagrams.

    In all cases, the SAME battery must not be used for both the 12v AND ground connections.

    If there are two batteries, then if one battery is for the 12v connected, the OTHER battery must be used for the Ground. In the case of four batteries again, whichever battery is used for the 12v, the opposite one in the chain must be used for the Ground connection.

    This ensures the load travels through all batteries equally instead of the one with both connections carrying most of the load. It’s how I have read elsewhere to gain the most even usage of the battery bank.

  15. Art Martinez

    Wow… the 12v battery connection was already covered by Jim in July 2009. I missed his post. Sorry about that.

    Regarding the battery charger, I use a disconnect switch to isolate the batteries, then use the Battery Minder. Check the directions for your unit, but mine says to disconnect the battereis so that there is nothing using the batteries while this charger is trying to do its job (like a propane alarm). I am able to keep my rig connected to shore power while in storage and the Battery Minder is powered this way, then the charge wires are run to the isolated batteries. Otherwise I’d have to remove the batteries to keep them charged and conditioned. I also don’t worry about freezing temps because of where I live.

  16. RoadToad

    @ Art & Jim:
    Yes, however, wiring diagrams are not INCORRECT. What you are addressing is the voltage drop over a longer length of cable issues. As long as the wire gauge is adequate for the load, makes no PRACTICAL difference which battery post the respective cable goes to first. The art work might be prettier if drawn symmetrically; but the electrical characteristic is not altered. To be absolutely balanced to the nano-amp, the depiction would be a “Y” assembly into each “like” end of the batteries. Again, totally inconsequential to the application being applied. It would be unnecessarily confusing to the non initiated to deem the diagrams to be “wrong”. Yes, it is a better practice to balance the cable lengths; but rather a mute issue really.

  17. Scott.S

    Jim that site you have is a good one but is that for 12V or 6V setup.

  18. Scott.S

    What is the best way to hook up 3 6volt batteries and a systom to keep them maintained.

  19. daveinwa

    Did this mod last year. I got two 6 volt batteries from Costco, they were taller and wouldn’t fit the battery boxes I had. Found taller battery boxes on a web site on-line. Easy mod!

  20. Bob

    Will there be any sparks or problem when I hook the positive of one 6 volt to the negitive of the other?

  21. sandy

    just wondering if this mod could be done with a gel battery.
    by switching these batteries does this help to run more things in the trailer(microwave,tv etc)and if it does not what can i do to increase the power without running the generator all day long.

  22. Jeff

    Just a couple of questions, I currently run two deep cycle 27 size 12 volt batteries. would I need to run three six volt batteries to increase AH or will two do it. If three are needed, how do you wire it to keep twelve volt production.

  23. regis101

    Here’s a link that has diagrams about half way down.

    You can’t use just three. Two or four

  24. Keyair

    Did this on my 1984 Airstream Motorhome.
    It was a little more involved, but I am super happy!
    My battery tray was rotted out, so I cut out the floor, dropped it 2.5″, strengthened the floor and drawer, replaced the slides with 500LB rated units too.
    Just have 2 6V’s for now, but I could fit 8 if and when I want!

  25. Jan Tollefsrud

    We just bought a 2011 keystone 3400TL 5th wheel and can’t find the power switch to the batteries! Can you HELP?

  26. sdayman

    This mod has been tempting me for a while. Now that I have a bigger tow vehicle that can handle a heavier tongue weight, *and* Costco batteries are so darned affordable and still have a good reputation, I started the mod today. One battery fit in my existing battery box and the other one is covered until I get a second box.

  27. nuukem

    Great write up! Where can I find the dual 6v battery box shown in image 6? Thanks!!

  28. Bodo

    I believe the parallel wiring diagramm you show is wrong and not good for your batteries.
    Current should flow trough all batteries, from +(batterie 1) to - (batterie 2)
    so a correct parallel wiring would look like this:

    My own experience is, that battery 2 will not charge correct (or not charge at all) from the solar and converter, because batterie 1 will charge first and move the converter already in “float charge” mode. Battery 2 will be empty after some weeks.

  29. Bodo

    Just to let you know my experience. I had it parallel wired for many weeks like your diagramm shows, until I realized battery 2 is complete empty.
    I have a solar, inverter and RV charger connected.
    I disconnected battery 1 and only connected battery 2, just to find it out was discharged (while the first one had 2/3 charge)
    I fliped batteries and charged battery 2 alone

    Both batteries are exact the same age (8 months old) from the same company, same specifications.

    Now I wired it with every (-) on the 2nd battery, not on the first one. (Still parallel connected batteries of course)

    I recommend to wire 2 12v batteries like this:


  30. RVONE

    Happy Camping!

  31. Par

    Want to connect two 12 volt batteries with two 6volt batteries. Series and parallel Will all batteries charge. I need wire diagram. Not sure if second 12 volt batterie. Will charge

  32. dbglide

    seems the misinformation is from rvone. most modern converters have a three stage output mode for maintaining your batteries. no one uses isolation diodes since the stone age. diodes have a .7 volt parasitic voltage drop which will never allow a battery to fully charge. if two batteries in parallel wont charge both I guess every diesel truck and piece of heavy equipment on the road that has dual batteries has at least one dead one for show. amp hours are amp hours weather it be from two 6 volt in series or two 12 volt in parallel. the biggest advantage of golf cart batteries are they are true deep cycle batteries and can stand more deep discharge/charge cycles than a non true deep cycle battery

  33. Dale

    I have a 31 ft TT. Bought a dual 6V battery box (that seemed to be harder to find than batteries). I want to swap up to 2 6V batteries. I understand the wiring diagram. Not complicated. My TT has your basic converter that comes with a Kodiak TT. I understand I don’t need to do anything else if I stop there.

    That said, I read that I need a specific charger for the 6V. And, If I add a generator, I read that I will need to use the charger for the batteries if I spend a weekend+ without shore power. This part I am unsure of. I’m no idiot but I just bought the trailer a week ago and yours was the simplest piece to read and digest vs forum strings.

    1. Do I need a specific charger for the 6V batteries and if so can I charge them both at the same time wired together? I doubt it.
    2. Seems simple enough to connect a generator to a charger to a battery,
    3. I should also buy a battery monitor and it will need to be wired in, throw in a new ammeter. I digress.

    Lastly, If I continue to add batteries, 2 more, then I read that I’ll need a new inverter/converter especially if I add a small solar panel. That’s probably a longer answer

    I appreciate this mod write up. It’s a jungle out there

  34. Cliff Odell

    No problem.
    12 Volt charger is what you want to use.
    The two 6 volters in series is just a 12 volt “stack”.
    Locate the cable that connects your 1st battery to your 2nd battery.
    This is the “middle” of your 12 volt “stack”
    Connect the 12 volt charger with Neg lead to the negative (-)terminal of the battery that has its positive (+) at the “middle”.
    Connect the 12 volt charger Pos lead to the Positive terminal of the other battery.
    This spans the stack.
    +12 at the “Top”; -12 at the “Bottom”.

2 Trackbacks For This Post

  1. Dual Trailer Batteries? - Ford Truck Enthusiasts Forums

    [...] Check out this article about replacing an RV 12-volt battery with 6-volt batteries: Mod #1: 6-Volt Batteries | ModMyRV [...]

  2. Battery/ies for travel trailer - DODGE RAM FORUM - Dodge Truck Forums

    [...] ^v batteries aren’t really any more expensive than 12v. They do put out much more charge and they last a lot longer. They’re great for dry camping. Check out Costco for batteries. Here is how to do it. RV 6-Volt Golf Cart Battery Upgrade | ModMyRV] [...]

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