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Should I Use Six Volt Deep Cycle Batteries as House Batteries in My RV?

by Daniel
(Ca.)

Why You Should Use 6 Volt Deep Cycle Batteries as House Batteries in Your RV

Why You Should Use 6 Volt Deep Cycle Batteries as House Batteries in Your RV

What is the best setup for a fifth-wheel trailer as far as batteries? The dealer said one 12 volt was plenty for 3-5 days. The manufacturer said two 6 volts would be better. The manufacturer said they do not set up the battery, which was the dealer's choice because it was cheaper. Why doesn't the manufacturer set up the battery? Sorry, two questions. Thanks for your help.

ANSWER Hi Daniel, some RV Manufacturers let the RV Dealer put the batteries in. This way, either the customer or the dealer can decide what type of batteries to use to provide the power to the RV's house portion.

Your 5th Wheel Manufacturer is also correct in stating that in most cases 2 six volt Deep Cycle Batteries are better than 1 twelve volt battery.

I am going to try to give you an explanation without getting too technical. There are three types of batteries that we are going to discuss here. I will give you the pros and cons of using them to power the house portion of your 5th wheel. What these batteries are used for is dictated by how they are constructed.

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Starting or Cranking Battery: Just as it name implies it is a battery that is designed to crank over an engine to get it started. It provides a powerful short burst of energy and is not designed to provide power for a long period of time. It is also not designed to be discharged and recharged often; the life span of this battery will be greatly reduced if it is used to power the 12-volt system of a 5th Wheel. It will also not provide power for as long as a Deep Cycle Battery.

RV/Marine "Deep Cycle" Battery: This is a cross between a Cranking and true Deep Cycle Battery. It can provide enough short burst energy to start the engine, and it can provide power to the house portion of the RV for longer periods of time than a Cranking Battery but not as long as a true Deep Cycle Battery. It can also be discharged and recharged more often than a Cranking Battery but will not last as long as a true Deep Cycle Battery. Again I would
not recommend this battery to power your 5th Wheel.

Trojan T-105 6 volt Deep Cycle Battery

True Deep Cycle Batteries These batteries like the Trojan T-105 6 volt Deep Cycle Battery (pictured above) are designed to provide a small amount of power for a longer period of time. They are definitely not designed to crank over an engine. They can be charged and discharged more often and last longer than either the Cranking or RV/Marine Batteries when it comes to powering the 12 volt accessories in an RV.

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Most RV Experts and RVers agree that 2 six volt Deep Cycle Batteries hooked up in series will provide power for longer than 1 twelve volt Deep Cycle Battery.

Depending on the size and use of the RV, some RVers have 4 Six Volt Deep Cycle Batteries hooked in Series/Parallel (see picture at the top of the page), which will theoretically provide this low-level power for twice as long as 2 six Volt Deep Cycle Batteries hooked up in series. This is especially important if you will be doing a lot of boondocking (camping where electricity is not available).

If your RV is equipped with a solar charger, it will also extend the length of time that this power will be available to you. If your 5th Wheel is equipped with a generator, you can also run the generator to refresh these batteries.

Bottom Line: Even though I do not know the size of your 5th Wheel or its intended use, I agree with your 5th Wheel Manufacturer's recommendation of having two six-volt Deep Cycle batteries to power your RV. If your 5th Wheel is very large or you intend to do a lot of Boondocking, then I would suggest the 4 six volt Deep Cycle Battery setup. I would definitely not accept the 1 twelve volt battery option. These options may end up costing you more initially but could save you a lot of problems down the road.

If any of our visitors want to add their opinions, they can do so by clicking on the "Click Here To Add Comments" link located at the bottom of this page.

Good luck with your new 5th Wheel and Happy RVing.

RVing Al

Comments for Should I Use Six Volt Deep Cycle Batteries as House Batteries in My RV?

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starstarstarstarstar 		more??? on 6 or 12 volt house batteries
by: Clare

This is true EXCEPT - as I noted before - if you have 2 mismatched batteries in parallel - or of one fails shorted (the most common failure in lead acid batteries) the bad battery will discharge the "good " battery - and you end up with TWO DEAD BATTERIES.

A "battery" is a string of cells in series - and using 2 6 volt batteries you build one large battery. Connecting 2 12 volt batteries in parallel you still have 2 batteries - - - -

The EXPERTS say 2 six volt batteries in series is preferred over 2 12 volts in parallel - and I HAVE to agree with them - both in theory and from practice.
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starstarstarstarstar 		6v vs 12v batteries
by: AnonymousJeff L

Assuming BC2 6v batteries vs Group 24 12v batteries:

A quality 6v battery will have a rated 225ah of capacity. Wire two in series to achieve 12v, however the rated 225ah (ea) will remain the same.

A quality 12v battery will have a rated 85ah of capacity. Wire two in parallel will still be 12v but the rated ah will double to 170ah.

As you should only ever use 50% of capacity, the 6v system will have a usable ah of 112.5, the 12v system will have a usable ah of 85.

The 6v batteries cost more and if one dies the system is now 6 volts and unusable. The 12v system is cheaper, but has the advantage of redundancy if one battery dies.

So, 6v system has the advantage of capacity and the 12v system has the advantage of redundancy and cost.
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starstarstarstar 		Very Interesting!
by: Charlie

Rather than two 6 volt batteries in series, why not use two 12 volt batteries in parallel? More strength and twice the amp hours.
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starstar 		Inefficient tech
by: Mike B

Lifepo4 lithium batteries are the way to go. Deep discharge, long life, cheaper over the lifetime of the battery. Want to learn more look up Will Prouse on YouTube. Tons of info.
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starstarstarstarstar 		6/12
by: Ken

I am wondering about the 12v being the one for large draw for starting vs 6v for sustained lower draws ? I have an inverter and have tried both 12v and two 6v to run 1500 watt appliances such as coffee makers with different results. The two 6v don't like the larger draws and the 12v can handle larger short time draws, so now which batteries do I use or purchase ?
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starstarstarstar 		Capacity
by: Anonymous

A major. reason is capacity and the ability to physically handle batteries. It’s all I can do to handle a single 12 volt 100 amp hour battery physically due to weight and maneuvering it in the RV. The same is true for a 200 amp hour 6 volt battery which approximates the size and weight of a 12 volt 100 amp hour battery. You would need a fork lift. to move a 200 amp hour 12 volt battery. Therefore, if you desire more capacity the solution is two batteries, either two 6 volt 200 amp hour batteries in series (which I prefer) or two 12 volt 100 amp hour batteries in parallel. Physically they require about the same space. Your choice depending on the capacity you want/need. As an amateur radio op who takes radios on trips, I run higher capacity (amp hours) and want the 200 amp hours for that and other electrical demands.
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star 		batteries
by: csnyder

I gave a detailed explanation of "batteries" a while back. The IDEAL setup is a single string of cells in series (the definition of a battery) Get the biggest cells you can get - ie the highest amp hour capacity you can buy, regardless of voltage, and connect them in series to get the voltage you require. Each lead-acid cell is nominally 2 volts - so a 3 cell "battery" is 6 volts, and 2 6 volt batteries in series (6 cells) is 12 volts.

The second best, by quite some margin, is a set of PERFECTLY MATCHED batteries in parallel. This sums the capacity - so you get double the capacity of a single battery at the same voltage.

If the "batteries" are made up of 2 sets - like 2 six volt batteries in series, a series-parallel connection will help keep the connection resistances balanced, and therefore better balance the load - ASSUMING the cables used to do the parallel connections are IDENTICAL. Otherwise, you are wasting your time and effort.

There is no such thing as "too much battery" - as long as your circuit protection (fuses or breakers) are properly sized to protect your wiring. you could have a bank of 100 200aH batteries connected in parallel and your load devices would not know the difference from one 50 aH battery as long as the 50ah could provide enough current to run it. The only thing that can cause a problem is too much VOLTAGE.

The only problem with "too much battery" is not having adequate charger capacity to re-charge the batteries. If each battery requires 10 amps to charge it and you have 10 in parallel you need 100 amps of charging capacity.

For coach batteries deep cycle batteries are ALWAYS better than SLA (starting lighting and accessory) batteries - and as long as your deep cycle battery pack is adequately sized it can be used to start your generator
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starstarstarstarstar 		Manufacturer provided batteries.
by: Frank

Manufactures don't provide batteries for mainly two reasons. It's cheaper, yes but also if batteries were provided by the manufacturer dealers would either have to run power to all of the RVS on their lots or remove the batteries and place them in a climate controlled storage area.

Batteries need to be either trickle charged or fully charged to prevent freezing in cold winter climates. Even if they are removed and stored indoors they would still need to be charged before they are reinstalled for sale. This means having a place to store them, a charging facility and the labor to remove and reinstall them.

Also if you are going to store and charge more than a few batteries it takes a facility designed and built to code with special exhaust means.
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starstarstarstarstar 		more "clare"ification
by: Clare Snyder

It depends on the amp hour rating of the batteries. If you have 2 12 volt 50 Ah batteries in parallel youi will (theoretically at least) have the same capacity as 2 100AH 6 volt batteries in series.

That said, it is a lot easier to buy 110 or 115 AH 6 volt deepcycle batteries than 55 AH 12 volt deep cycle batteries as REAL 12 volt deep cycle batteries are not a common consumer item like 6 volt golf cart batteries (they sell 10s of thousands of them every year).

And yes, the golf cart batteries WILL start your generator (as long as you start the generator before the batteries are run down)
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starstarstar 		series vs parallel battery connections
by: clare Snyder

First, you need to define a few terms. A BATTERY is a SERIES connected string of CELLS.

A 6-volt battery contains 3 cells. A 12-volt battery contains 6 cells.

In a SERIES connection, the total voltage is equal to the sum of the voltages of all cells, and the current is equal to the current produced by the poorest cell in the battery.

When charging, all cells in the series string get the SAME CURRENT. The charging voltage across each cell may differ until the battery has become EQUALIZED. When all 6 cells are fully charged, unless one or more cells has a serious problem, the voltage across each cell will be virtually identical at 1/6 of the charging voltage.

Putting 2 cells, or 2 batteries, in PARALLEL, means the voltage across each is identical and does not change with the number connected in parallel. HOWEVER - one battery can supply more current than the other, and can take more charge current than the other - and if the intrinsic voltage of one battery is higher than the other, the low battery can discharge the higher battery trying to equalize themselves. This can damage BOTH batteries.

So, in effect, 2 6 volt batteries IN SERIES is ONE BATTERY.

2 12 volt batteries in parallel will ALWAYS remain 2 batteries - with the possibility of a war between them if they are not 100% IDENTICAL in age, construction, and condition. (and the condition WILL change with age - and at different rate for each)
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starstarstarstarstar 		Six Volt Versus 12 Volt
by: Old Prospector

In my previous comment (two versus one) I asked if two 6V batteries wired in series would last longer than two 12V batteries wired in parallel. What I was referring to is that right now I have two 12 Volt batteries wired in parallel on my Tear drop trailer, and they are almost worn out and will shortly need to be replaced. My wife and I usually boon-dock in dispersed camping sites, so there is no hook-ups. So, I was wondering if the charge in two 6V batteries wired in parallel would last longer on a charge than the charge would in two 12 Volt batteries wired in parallel. If so then would it be - Such as 1 day, 2 days, 3 days etc., the same, or less, than the 2 12V batteries?
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starstarstarstarstar 		Two versus One
by: Old Prospector

Roughly (I know it will depend upon amount of use and how much amperage draw, that's why I say roughly, I just need an opinion of a rough estimate (guessed-a-ment)), How much longer would two 6V deep cycle batteries wired in series to obtain 12V output last versus 2 12V deep cycle batteries wired in parallel? - 1 day?, 2 days?, 3 days?, etc..
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starstarstar 		Yeah but....
by: Bob

You haven’t explained why 2 deep cycle 6V batteries in series are better than 1 deep cycle 12V battery.
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starstarstarstarstar 		Mains Battery chargers
by: J Parmar

I recently had my electric cars batteries replaced. I saved the old batteries to deal with power outrage. Would a standard 12v battery charger be adequate to charge six 6 volt batteries wired up in series / parallel?
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starstarstarstarstar 		Good to the point reasoning
by: Anonymous

The article quicky explains the reasoning why deep cycle batteriems are better, and does so in a short and easy to follow manner
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starstarstarstarstar 		Charge indicator?
by: Anonymous

Is there a gauge you can buy that tells you how much charge your system has and when you need to recharge?

Battery Charge Gauges

Answer: Yes you can purchase aftermarket battery charge gauges like the one pictured above. I hope that helps.

Happy RVing!
RVing Al
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starstarstarstarstar 		4-6v batteries
by: Arve

If I hook up 4-6v batteries in series-parallel to get my 12v output, using true deep cycle batteries, can it use this setup to start the generator? It's an Onanistic 5500...
Thanks

Note From RVing Al: For more information on how to wire 2 or 4 deep cycle batteries take a look at the wiring diagrams that I added to the top of this page. Most RV generators are connected to the House Batteries and that is what starts the generators.
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starstarstarstarstar 		4 x 6 volt batteries!!
by: Anonymous

Interesting, however 4 x 6 volt batteries in parallel will only increase the amperage, the voltage will remain at 6 volts.

I am sure you mean a series parallel connection which will increase the voltage and amperage.

But the danger then is using a higher amperage than the system is and was designed for. This in turn can blow circuits and create a fire risk..
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starstarstarstarstar 		6v battery conf.
by: Anonymous

can three 6v be conf. with 2 in parralel and 1 in series?
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starstarstarstarstar 		can two 6v start my generater
by: Anonymous

I have two 12v and am thinking of going to 2 6v, will they start my onboard gen?

Comment from RVing Al: Yes they should have no problem starting your generator.
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starstarstarstarstar 		question why one boiled over
by: AnonymousM

5th wheel is 32ft hot weather, why did one 6volt boil and run over. fed by solar panel,did the charge from the sp dry them..why did only one boil over.
I really understand that 2 6vltare best. they are expensuive and dead. donot want to have it happen again. 5th wheel has a dial i.e. off one both.
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starstarstarstarstar 		Trojan T-105
by: Anonymous

We have a small camp in the middle of nowhere that weve had for 20 years. The electrcal setup is 6 trojan t -105 (6 volt) bateries wired in paralell series to create 3 12v bateries. those bateries are trickle charged by a solar panel. the bateries feed an inverter to power the AC oulets in the house.We got 10 yrs out of the first set and we are about to replace the second even though they still work. Thats 10 YEARS per set!!! what more do i need to say
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starstarstarstarstar 		4 batteries series/parallel
by: Mel

2 - 6 volt batteries in series are better than 1 12 volt for power duration.

Anonymous is right - the 4 - 6 volt batteries should be hooked up 2 sets of 2 each in series and then both sets hooked in parallel - just as detailed in his comments.
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starstarstarstarstar 		How do I tell the difference
by: PaPaFrank

I am new to RVing and plan to do a significant amount of boondocking. I would like to upgrade my RV house batteries, how do I distinguish "a true deep cycle battery" from a "Marine/deep cycle battery"?
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starstarstarstarstar 		4 6v vs 4 12v
by: Anonymous

Asking the same 6v vs 12v question... I have 4 6v batteries powering the inverter side of my coach. If I replace those 4 6v batteries with 4 12v marine/rv deep cycle, is that a better solution?
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starstarstarstar 		4 battery hook up
by: Anonymous

Using 4 batteries you would want to setup a series parallel circuit, not series, to get 12 volts. Four 6v batteries in series +-+- = 24v. Connect 2 sets of 2 batteries in series, B1- to B2+ and then connect the 2 sets in parallel B1+ to B2+|B1- to B2- to equal 12v.

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