Maximum - 12 volt Deep Cycle Batteries Connected in Parallel

The only thing "wrong" with balancing paralleled RV batteries is "it's being too picky" or "it has too trivial of an affect to mess with".

As usual, ignore things you think are minor considerations at your own peril, or alternatively ... ignore them to save time and money. ;)

As for me, my 12 volt RV batteries are ganged together balanced ... just in case it helps.

Yet another case due to confusion. There are far too many desk-bound theorists who seek to uncover "findings" and arrive at assumptive conclusions. Because their "finding" is published either electronically or on lob-lolly pine their assumption is taken as "gospel". I fought this utter nonsense for 30-years. One ended in a near-war with Delco and their calcium/calcium "Deep-Cycle" battery. Model Voyager.

The entire concept of desk-bound-conclusions really screws the pooch when trying to access accurate information. Reality testing, and factual white papers countered desk-bound fallacies. It paid a good wage but the practice continues unabated.

The "Bigfoot Grade" desk bound battery cable length fallacy can be quashed at home with a minimum of effort. I suggest doing exactly that if in doubt.

pnichols wrote:
Method 3 in this link can be used to connect any number of 12 volt RV batteries in parallel so that they are are balanced:
http://www.smartgauge.co.uk/batt_con.html

When this can be pretty educational, I doubt it practical use.
99% of batteries die becouse of age, or mishandling so what small misbalance can change here?
I drive dual batteries vehicles for 30 year (talking about wagons and trucks). None of the manufacturers ever made an attempt to balance the batteries. It is always that pretty long cable goes from 1st battery and connects to main clamp on the 2nd.
Would you think that major truck manufacturers could consider battery balancing if that would made real life difference?
Our latest ECO sedan has main battery under the hood, while ECO engine starting battery in the trunk. Talk about well over 15 feet of cable between.

David,

The negative effects on batteries of not balancing only become significant over time. Real-time measurements - especially with large cabling - will show only small differences between balancing or not balancing.

Of course, the negative effects over time will be greatest for RV'ers using their batteries for large current draws often (i.e. microwave, coffee maker, induction cooking, convection oven, etc.) and also for RV'ers applying large currents often for quick recharging. The imbalance is greatest in these situations, but it will still take it's toll on batteries only over time - just more so.

Read the entire article in the link that I gave. The reasoning there makes excellent electrical and battery long-term sense.

What "balanced" means is simple: The total wire length and type from every positive battery terminal to every load or charging source in the RV must be identical, and the total wire length and type from every negative battery terminal to every load or charging source in the RV must be identical

A simple test will intensely "question" your assumption. All connections being sound test two batteries. One with foot long 1 awg cables, the second with ten feet long 1 awg cables. Apply say a 50 amp potential. Surprise!

It takes a lot of differential meaning cable length difference to cause a significant difference. .01 volt is not significant. Assurance is made by using sufficiently appropriate awg conductor. The differential would become objectionable if 10 gauge wire wire substituted for the 1 awg and I am talking purely the difference in cable length versus voltage differential. This can be expressed with circular mil resistance versus ampacity per foot, formulas but why bother?

Yes .... you can gang any number of 12 volt RV batteries together in parallel so long as you have them connected in a balanced manner to get even sharing of current among them when charging from RV charging sources, and even sharing of current among them when discharging into RV loads. A buss bar is not necessary, or even optimum from a pure electrical principles perspective.

What "balanced" means is simple: The total wire length and type from every positive battery terminal to every load or charging source in the RV must be identical, and the total wire length and type from every negative battery terminal to every load or charging source in the RV must be identical. The electrical lingo version of this is: The DC resistance to electrical current flow from every positive battery terminal to evey load or charging source in the RV must be the same value for each battery terminal, and the DC resistance to electrical current flow from every negative battery terminal to every load or charging source in the RV must the same value for each battery terminal.

Method 3 in this link can be used to connect any number of 12 volt RV batteries in parallel so that they are are balanced:
http://www.smartgauge.co.uk/batt_con.html

Either Method 3 or Method 4 in the link above can be used to connect four(4) 12 volt RV batteries in parallel so that they are balanced.

It's obvious that using Method 3 can provide balance for any number of batteries in parallel. You can see - with some careful study - that Method 4 provides balance for four(4) batteries in parallel. Probably the Method 4 approach could also be used for any number of batteries in parallel too ... but you would have to carefully diagram this out so as to keep all total wire and type lengths identical for balance.

It depends upon individual situations whether the Method 3, or Method 4 connection method would be "simpler".

If you need such big battery bank, you might evaluate your power consumption.
I had 4 GC batteries in my conversion and even before LED lights I could use them for lighting, water pump and 1l of hot coffee made every morning + occasional microvawe use.
On usual camping it took me 3 days before I had to start generator.
You can always substitute the weight of the batteries with the weight of solar panels or weight of generator.
Obviously you will find guys who will want to run washer & dryer on battery power.

BC_Explorer wrote:
Is there a max number of 12 volt batteries that can be connected? For example, could I connect 3 or 4 batteries in parallel?

The only thing I will say about six volt in this thread is this:
There are no six volt batteries in RV's.. Only 12 volt batteries split into two halves for ease of handling. (Yes each half is six but. Well think 4D and you have it)

Now to the O/P's question.. Is there a limit?

There are indeed limits but not electrical/electronic.
There is a limit as to how much WEIGHT your RV can carry. For eample I only ahve about 1,000 pounds of cargo carry capacity so when I add up all the "Junque" clothing, food, cleaning supplies and such, subtract from 1,000 I can add that many pounds of LEAD (er, batteries)

There is a practical limit.. Eventually you run out of places to put 'em.

And those are your limits...

BobsYourUncle wrote:
Most important consideration is that the batteries are all of same strength. Don't mix old weak ones with new strong ones. Weak will sap strong.

CONCUR !

I would also add, flooded cell batteries are probably better because you can use a hydrometer to test for individual cell strength. It is important that they all equal,

time2roll wrote:
Technically you can have as many as you like but the chances of trouble start increasing. To keep them balanced you may need a bus. As a minimum attach the main feed vs ground at each end of the stack.

I don't know that physical type/style of connection really matters as long a it is adequate to handle the current.

Our coach came form the factory with 6 12-vold AGM coach batteries as standard equipment.

Tom