Running 12V Batteries in Parallel

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CassandraS

CassandraS

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Joined
Apr 26, 2017
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22
Location
Minnesota
Hey guys!

Quick question, I'm looking into purchasing an additional battery and run it in parallel to increase my longevity while dry camping. The issue I am running into is I cant seem to find a battery box big enough to house both batteries.

Do any of you have a similar set up? Recommendations on where I could maybe find something that would work? Pictures of what you've done with yours?

Any info/advise would be great!

Thank you!!
 
If the battery is mounted on the trailer tongue, there should be enough room to slide it to one side and put a second battery in the same kind of box next to it.  The boxes are available at almost any RV or auto parts store.

When you connect the batteries, run two cables between them, (+) to (+) and (-) to (-).  Then stagger connect the batteries to the trailer - use the (+) on one battery and the (-) on the other.

This equalizes the wire lengths and number of connections between the trailer and each battery so they'll charge and discharge equally.  If you connect both of the trailer wires to one battery, it has a shorter path going to and from the trailer than the other one and the batteries will tend to become unbalanced, with the closer battery doing the majority of the work.
 

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I found several by googling "battery boxes " . You need to know your battery size.
 
To the OP. In your pocket you probably have a cell phone with a nice camera on it. Make sure you take a lot of photos of how the wires are connected before you unhook everything. All too often people unhook the wires and then can't figure out how they go back on so they guess and if they are wrong they start smoking things.
 
If you build a frame of some type you can stack 4 batterys together. If you have AGM batterys you can lay them on their side if need be. I have 2 HB's from the factory in the Class A. Added 3 more in the storage compartment just forward of the factory location which keeps the cables on the shorter side which is desireable. I know you have a TT but you can figure outwhat works for you. Have fun!
 
One more thing ... if your existing battery is the original one, you should get two new batteries, not just one.  You already have 2-3 years on the first battery so a good portion of it's expected life is already gone.  Older and newer batteries don't work well together.

If you're buying two batteries, a pair of 6 volt golf cart batteries will work better and give more bang for the buck than a pair of 12 volt batteries.  Each cell on the 6 volt batteries will be twice as large with more rugged plates than the ones on a a pair of 12 volt batteries.  These are good things for extended boondocking.
 
Lou Schneider said:
One more thing ... if your existing battery is the original one, you should get two new batteries, not just one.  You already have 2-3 years on the first battery so a good portion of it's expected life is already gone.  Older and newer batteries don't work well together.

If you're buying two batteries, a pair of 6 volt golf cart batteries will work better and give more bang for the buck than a pair of 12 volt batteries.  Each cell on the 6 volt batteries will be twice as large with more rugged plates than the ones on a a pair of 12 volt batteries.  These are good things for extended boondocking.
Click to expand...


I will agree with Lou, as a professional, the last thing I would do is specify a parallel string of FLA's. batteries or more particularly, cells, come in voltages from
2, 4, 6 and 8 Volts.. there is almost always a correct solution without requiring paralleling. that said, this is an RV application and many RV'ers don't need or require a technically correct solution. I would suggest you throw away your old 12V battery and purchase two golf cart deep cycle 6V batteries and connect them in series
and avoid all the issues of parallel operation. If you insist on parallel operation then only 2 strings max. connecting batteries in parallel will shorten lifespan considerably due to unbalanced charging and discharge cycles.

 
https://www.amazon.com/gp/product/B000VU98HK/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
i fit 4 6 volt interstate golf cart batteries in this
hope this helped ::)
 
Each cell on the 6 volt batteries will be twice as large with more rugged plates than the ones on a a pair of 12 volt batteries.
Click to expand...

That depends on what brand & size 12v battery you buy, but a pair of 6v GC2 type battery is almost always lower in cost than equivalent quality/capacity 12v deep cycles.  That's why you get "more bang for the buck".
 
Gary RV_Wizard said:
That depends on what brand & size 12v battery you buy, but a pair of 6v GC2 type battery is almost always lower in cost than equivalent quality/capacity 12v deep cycles.  That's why you get "more bang for the buck".
Click to expand...

True enough if you're talking about a GC2 6 volt battery compared to a  4D or 8D size 12 volt battery that's twice as large and twice as heavy as the GC2. 

But when you're talking about using a pair of 6 volt batteries to replace a pair of similar sized 12 volt batteries (Group 24 or Group 27), the 6 volt cells will be twice as large as those in the 12 volt version, simply because the pair of 6 volt batteries only have half as many cells as a pair of 12 volt batteries.

Sorry I didn't make that clear, but somehow I doubt Cassandra has a 4D or 8D battery in her Jayco travel trailer.  Although that could be a (more expensive) option if there's room on the tongue.

 
A GC 2 has about the same footprint as a Group 24 smaller than a 27 or 29 but they are TALLER.
So if any "Group" battery fits odds are a GC-2 will as well. you may need to "Shim" it in some battery boxes.

They are cheaper due to their popularity (GC=GOLF CAR.. By the pallat load at most Courses).

Two GC_2's in series are indeed the same weight et-al (Including capacity) as a 4D.

But way easier to wrangle.. They are also DEEP CYCLE. Most Group-xx batteries are MARINE/deep cycle (Did you notice that I changed case)  This makes a big difference in how much power you can use, and how long they last.

This is why I'm big on GC_2's.  THey give you way more "Bang" for your buck.

 
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