Hooking up more then one battery - Motorhome Forums, Motorhome Discussion, Motorhome Chat

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post #1 of 10 (permalink) Old 18-11-2019, 12:18 Thread Starter
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Hooking up more then one battery

So I went to an Rv guy who explained to me how the rv works and everything and he gave me 3 rv batteries.
He said that those batteries would last longer then the one I have because they are made for rv while mine aren't
But here is the problem.
My rv run on 2 6v batteries and together they make 12 volts.
But the ones the guy gave me are already 12 volts EACH.
He wanted to connect two of those batteries TOGETHER because he thinks that it will give me more power.
But I did'nt want to because me thinking logically I find that if 2 6v batteries make 12 volts then two 12 volts will make 24 volts and that will kill everything in my rv.
He insisted that it's not like that but I still didn't let him but I have the cables and everything to do it but I wanna ask first.
So is it ok to do this?
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post #2 of 10 (permalink) Old 18-11-2019, 13:23
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I think it depends on how they're wired John - in series or otherwise - but the experts will be along soon to help you out.

Jean
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post #3 of 10 (permalink) Old 18-11-2019, 13:28
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Don't quite understand what your saying. Are they 24v batteries? And what voltage does the van run on? 12 or 24? Some older Mercedes vans had a 24v starter but everything else was 12v.

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post #4 of 10 (permalink) Old 18-11-2019, 14:30
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Take the negative from your RV and connect to the negatives of BOTH 12V batteries.
Take the positive from your RV and connect to the positives of BOTH 12V batteries.
You will then have the 12V that you say came from your two 6V batteries, but with a lot more electricity storage available.
Bill
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post #5 of 10 (permalink) Old 19-11-2019, 10:45
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Quote:
Originally Posted by John Galli View Post
So I went to an Rv guy who explained to me how the rv works and everything and he gave me 3 rv batteries.
He said that those batteries would last longer then the one I have because they are made for rv while mine aren't
But here is the problem.
My rv run on 2 6v batteries and together they make 12 volts.
But the ones the guy gave me are already 12 volts EACH.
He wanted to connect two of those batteries TOGETHER because he thinks that it will give me more power.
But I did'nt want to because me thinking logically I find that if 2 6v batteries make 12 volts then two 12 volts will make 24 volts and that will kill everything in my rv.
He insisted that it's not like that but I still didn't let him but I have the cables and everything to do it but I wanna ask first.
So is it ok to do this?
I take it that you have two 6 volt batteries that have been wired in series to give you 12volts. You need to wire the two 12volt batteries in parallel. That's 1 positive cable[Red] + to + Negative cable [black] negative to negative. Now you need to wire your load cable, positive from one battery, but the negative from the other battery. Hope this helps.

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post #6 of 10 (permalink) Old 19-11-2019, 11:16
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I think we need more informative information please. We are all guessing the set up.

Ray.

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post #7 of 10 (permalink) Old 19-11-2019, 11:43
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Quote:
Originally Posted by David Cowley View Post
I take it that you have two 6 volt batteries that have been wired in series to give you 12volts. You need to wire the two 12volt batteries in parallel. That's 1 positive cable[Red] + to + Negative cable [black] negative to negative. Now you need to wire your load cable, positive from one battery, but the negative from the other battery. Hope this helps.
Ooh, I'm quite pleased with my comment at post #2 - I must be learning something about 12v electrics after about 12yrs on the forum!! So thank you all!
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post #8 of 10 (permalink) Old Yesterday, 07:25
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Wiring batteries if you have two six volts at say 100 amps each, negative terminal from battery 1 to van supply, then positive terminal from battery 1 to negative terminal of battery two, positive terminal of battery two to van supply, gives you 12 volts 100 amps.
If you have two twelve volts at 100 amps each negative terminal from battery one to van supply and connect a wire from battery one negative to battery two negative, do the same with the positive terminals but put an inline fuse between the two positive battery terminals around 20 amps and an inline fuse of around 50 amps between battery one and the supply connection. That will give you 12 volts 200 amps.
Some Motorhomes just connect the leisure batteries negative terminals to the chassis for earth, others have a dedicated connection so check which you have. Although I have explained how they are connected alway connect any positive connections first negative last if disconnecting always negative first. Assuming your van is negative earthed.
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post #9 of 10 (permalink) Old Yesterday, 14:54
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Quote:
Originally Posted by John Galli View Post
So I went to an Rv guy who explained to me how the rv works and everything and he gave me 3 rv batteries.
He said that those batteries would last longer then the one I have because they are made for rv while mine aren't
But here is the problem.
My rv run on 2 6v batteries and together they make 12 volts.
But the ones the guy gave me are already 12 volts EACH.
He wanted to connect two of those batteries TOGETHER because he thinks that it will give me more power.
But I did'nt want to because me thinking logically I find that if 2 6v batteries make 12 volts then two 12 volts will make 24 volts and that will kill everything in my rv.
He insisted that it's not like that but I still didn't let him but I have the cables and everything to do it but I wanna ask first.
So is it ok to do this?
Hi Ya - You are right to check. There are two options to connecting batteries:
1. In SERIES - this is where (if you can picture this as the batteries sitting side by side, short sides together so that all their terminals are in-line, like red, black of battery 1 then red, black of battery two ) your two 6 volt batteries have been connected in SERIES - which means they are connected like a 'Daisy chain' - i.e., black (-ve) of battery one is connected by a heavy guage wire to the red (+ve) of battery two then the remaining red terminal of the first battery is to be cabled to your RV's positive connection and the remaining black (-ve) of the second battery is connected to the negative terminal of your RV.
What this does is adds the two voltages together making 12 volts (note that the electric current generated with these two batteries connected in this way stays the same as that generated by 6 volts battery on it's own)

OPTION 2. In PARALLEL - NOTE that what this does is MAINTAINS the VOLTAGE AT 12volts through all three batteries BUT increases the current generated.
This is where you connect the batteries together with heavy guage cables so that all the red terminals are connected together in line & the black terminals of each battery are connected together in line (this makes them appear like the red and black lines are parallel if you picture them connected together one in front of the other with the batteries' matching colour terminals one in front of the other - the red terminal of battery 1 is connected to the red terminal of battery 2 - and also then connected to red of battery 3 if you are using all three AND the black terminals of batteries 1,2 and 3 are connected in the same way but with black wire, 1 to 2 and 2 to 3. It's then considered best to think of all three batteries as composing a larger 12 volt battery and to use the positive terminal of battery one to connect to your RV and the negative terminal of battery three to your RV. This is so the charge in the battery gets used through all the batteries from one end of the parallel lin-ep to the other. Thus will be more likely to use the energy equally through the batteries discharge cycle. IF you use ther red and black of the same battery then that battery will be discharged first and the next battery will be working inefficiently trying to move charge into the depleting first battery and then battery three will be doing the same to battery two and one. This is known to degrade / damage the battery cells.

Hope this info helps.

I would say, though - I am not an electrician and so would advise you to check out WILL PROWSE on YOUTUBE who is excellent at explaining electrical systems for RV's using 6v, 12v, 24v and 48v - to each of their separate advantages and you'll learn why 12v is best for a small setup in an RV. Also, consult qualified auto electrician for safety. Sparks, current and voltages can be dangerous.

NOTE - I mention heavy guage wires because the wires must be thick enough through the conductive material to manage the current that passes through - if wires used to conduct elecrtricity are too thin they heat up and catch fire which is why you'll see that different sized - the guage - of wires are given an Amperage Rating for the amps current they can safely conduct.

Finally, I'm pretty sure you would be best advised not to combine 6v and 12v batteries together in the same system - i.e., use 12v together or 6v together but not 2 x 6v in series to make one 12v then connected in parallel with 12v batteries. Likely unhealthy.

Best wishes. Ken www.savetimewebdesign.com
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post #10 of 10 (permalink) Old Today, 06:16
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I can't say it better than Bill further up the page, simply stated and correct.

"Take the negative from your RV and connect to the negatives of BOTH 12V batteries.
Take the positive from your RV and connect to the positives of BOTH 12V batteries.
You will then have the 12V"
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