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Open Roads Forum  >  Tech Issues

 > 6 volt vs 12 volt batterys

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richccc

CA

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Posted: 11/10/06 08:10am Link  |  Print  |  Notify Moderator

I have a 06 class C m/h with two house 6 volt batterys and I was wondering why they would put two 6 volt instead of two 12 volt batterys. I found out the hard way the chassis battery has more than just the truck drawing it's power from it. The entertainment center and the power step are drawing down this battery. My question is can I replace the two 6 volt house batterys and replace them with two 12 volt batterys. I want to rewire the entertainment center and the power step to draw from the house batterys. Is this ok to do? Would two 6 volt batterys be ok or am I wasting my time?


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dgc_61

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Posted: 11/10/06 08:18am Link  |  Print  |  Notify Moderator

You don't want to do that. You probably have more capacity in your 2 six volts than you would get by replacing them with 12 volts. What kind of batteries are they? I am sure someone here would have the numbers on capacities for you.


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wa8yxm

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Posted: 11/10/06 08:29am Link  |  Print  |  Notify Moderator

The reason to use a pair of sixes instead of 12's is more tradition than anything, however there is a positive reason to do it, First, the tradition:

Lead Acid batteries can be designed to put out great gobs of current, quickly and not for long, or they can be designed to put out a much slower stream of electrons but for a LOT longer time, The latter method yields more ampere hours (Which is what you want in a house battery) the former yields greater surge currents, (Which is what you want for a starting battery)

True deep cycle batteries are designed for providing a lower current for a much longer time, Starting batteries, a lot of current, Then we have "Marine/Deep Cycle" which is kind of half mashed medium current for medium time.

For an RV we want Ampere hours, lots of them. And for years the only TRUE deep cycle batteries were golf cart batteries, and those are six volt. Hence the tradition

Today, thanks in no small part to the large number of RV's we have true deep cycle 12 volt batteries, Pound for pound there is no advantage, Ampere hour wise, of one over the other.

So, what are the only remaining advantages of two six in series v/s two 12 in parallel

Well there are 2: 1: Fewer wires (1 wire less) and copper is EXPENSIVE just now, this means less labor and less to go wrong.

2: If, (Or should I say WHEN) a cell shorts, instead of 12 volt you have 10 Now if you have a pair of sixes in series, you still have 10 volt

But if you have a pair of 12's in parallel you still have 10 volt, but with a whole lot of current (2 volts divided by the internal resistance of both batteries and the parallel cables) flowing, the shorted batteries' remaining cells will boil and release Oxygen and Hydrogen in the magic 2-1 ratio and a spark in this cloud can be truly exciting. And may happen if the cables are not heavy enough.

That said. Either method works well and both are often used.


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hwybnb

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Posted: 11/10/06 08:35am Link  |  Print  |  Notify Moderator

I agree with the preceeding post.

It is not a question of 6 vs 12 but rather of the battery type. Your 6-volt batteries are probably Trojan T-105 or similar "golf cart" batteries that are designed for deep cycling. Most RV 12-volt batteries are "RV-Marine" types that are designed to provide high starting current for engines in addition to powering the lights and other loads. They do that but do not handle deep cycling as well.

It is possible to buy 12-volt deep cycle batteries but they are not as common as the 6-volt ones and are more expensive.

Compare the amp-hour capacities of the 6-volt batteries you have with whatever you are considering as replacements and choose what best fits your needs. You also have to consider case size and the amount of space you have of course.

CDK

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Posted: 11/10/06 09:12am Link  |  Print  |  Notify Moderator

Now I get it and others will also .

joemyers

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Posted: 11/10/06 08:40am Link  |  Print  |  Notify Moderator

Personally, if you already have the 2 6V I would stick with them and just rewire the aux's like the stereo into the house system. Doing everything over is not going to gain you any thing ecept a lot of rewiring. 12 volts is 12 volts anyway you get it. JMTCW

CDK

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Posted: 11/10/06 08:40am Link  |  Print  |  Notify Moderator

The above is pretty clear but this is where ya lost me[emoticon]

"So, what are the only remaining advantages of two six in series v/s two 12 in parallel

Well there are 2: 1: Fewer wires (1 wire less) and copper is EXPENSIVE just now, this means less labor and less to go wrong.

2: If, (Or should I say WHEN) a cell shorts, instead of 12 volt you have 10 Now if you have a pair of sixes in series, you still have 10 volt

But if you have a pair of 12's in parallel you still have 10 volt, but with a whole lot of current (2 volts divided by the internal resistance of both batteries and the parallel cables) flowing, the shorted batteries' remaining cells will boil and release Oxygen and Hydrogen in the magic 2-1 ratio and a spark in this cloud can be truly exciting. And may happen if the cables are not heavy enough.

That said. Either method works well and both are often used. "

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Posted: 11/10/06 08:49am Link  |  Print  |  Notify Moderator

CDK wrote:

The above is pretty clear but this is where ya lost me[emoticon]

"So, what are the only remaining advantages of two six in series v/s two 12 in parallel

Well there are 2: 1: Fewer wires (1 wire less) and copper is EXPENSIVE just now, this means less labor and less to go wrong.

2: If, (Or should I say WHEN) a cell shorts, instead of 12 volt you have 10 Now if you have a pair of sixes in series, you still have 10 volt

But if you have a pair of 12's in parallel you still have 10 volt, but with a whole lot of current (2 volts divided by the internal resistance of both batteries and the parallel cables) flowing, the shorted batteries' remaining cells will boil and release Oxygen and Hydrogen in the magic 2-1 ratio and a spark in this cloud can be truly exciting. And may happen if the cables are not heavy enough.

That said. Either method works well and both are often used. "


To put it simply, in the event of a shorted cell, two 6v batteries in series is a lot safer than two 12v batteries in parallel (which could possibly cause a fire or explosion).

CDK

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Posted: 11/10/06 08:56am Link  |  Print  |  Notify Moderator

Sorry I still don't get it?

hemi-kz

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Posted: 11/10/06 09:08am Link  |  Print  |  Notify Moderator

With 2 12v batteries in parallel, if one battery shorts a cell, you now have a 12v connected in parallel to a 10v. Batteries in parallel always try to equalize voltage, so the good battery will dump a lot of current into the shorted battery and the batteries will get very hot. Batteries in series (the way 2 6v are connected) do not try to equalize if they are at different voltages.


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