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:

Trojan 6-Volt T-105 Golf Cart Battery

Four 6-volt batteries mounted on tongue behind propane tanks

Custom battery box for housing 4 6-volt batteries

Tongue-mounted dual 6-volt battery box

End-to-end mounting of dual 6-volt batteries on tongue

End-to-end 6-volt battery box enclosure

Utility box for dual 6-volt batteries mounted in a 5th wheel

4 6-volt batteries mounted in front of 5th wheel in custom box

Another view of 4 6-volt batteries mounted in front of 5th wheel in custom box

Vent and sealing foam for 5th wheel custom battery box

Wooden battery box cover for custom 5th wheel battery box

Construction drawing of custom 5th wheel battery box

How to wire 2 12-volt and 2 6-volt batteries in parallel

How to wire 4 12-volt and 4 6-volt batteries in parallel

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:

Batteries
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

7 Comments For This Mod

1. cccale (February 23rd, 2009 at 10:28 pm)

   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 (February 24th, 2009 at 9:27 am)

   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 (March 8th, 2009 at 3:04 pm)

   How would I determine if I needed 2 or 4 batteries. (Based on dry camping and hours of use)
4. ModMyRV (March 8th, 2009 at 6:32 pm)

   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 (July 13th, 2009 at 10:26 am)

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

   See http://www.smartgauge.co.uk/batt_con.html

   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 (July 20th, 2009 at 6:38 pm)

   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:

   http://home-and-garden.webshots.com/album/571578652EwRHPm
7. kraythe (October 3rd, 2009 at 12:47 am)

   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?

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