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Old 05-15-2014, 05:07 PM   #1
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3 12 volt deep cycle in parallel question

On my MH I have 3 12 volt deep cycle batteries in parallel with the cables connecting the bank to the house running from the closest battery to the house.

Is there any problem with this setup?

Is there any difference if I were to move one of the connecting cables to the farthest battery? I have seen them both ways.

My concerns are the last battery in the bank when it comes to charging and getting full use of each battery.

Thanks
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Old 05-15-2014, 05:13 PM   #2
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Charge and load should evenly distribute , but you could check this site for more info.

The 12volt Side of Life (Part 1)
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Old 05-15-2014, 05:16 PM   #3
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Yes, basically you want one house cable connected to battery 1 & the other to battery 3. This gives a more even power draw off all three batteries & will extend the life of the batteries.
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Old 05-15-2014, 05:17 PM   #4
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For 3 batteries in parallel, the connections should be made to the middle battery, and from the middle one, parallel, to each of the other two.
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Old 05-15-2014, 05:22 PM   #5
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Hi LPD218,
With 12 VDC batteries connected in parallel, the connection from which battery does not matter. If you had 6 VDC batteries in series my answer would be different. The link Skip provided is excellent.
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Old 05-15-2014, 05:23 PM   #6
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what ever wires are used to charge them and pull power should be in the center of the set

too slow MJ56 has it right
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Old 05-15-2014, 06:04 PM   #7
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Laws of physics prevail here. It doesn't matter where the connection is made the current and voltage will be the same on each of the positive legs and each of the negative legs
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Old 05-15-2014, 08:19 PM   #8
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3 12 volt deep cycle in parallel question

With batteries in parallel it makes absolutely no difference whatsoever which batteries the power feed lines are connected to. The whole purpose of wiring them in parallel is to make them electrically one big battery.


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Old 05-15-2014, 09:48 PM   #9
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Physics and in particular, Ohm's law is the reason it does make a difference.
Least and equal resistance is the principle, just like sizing wire for current draw makes a difference.

One of the quick tips or links often posted here, explains it, with pictures.
The OP asked the correct questions and got the correct answer.
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Old 05-15-2014, 11:01 PM   #10
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Quote:
Originally Posted by HuntingHawk View Post
Yes, basically you want one house cable connected to battery 1 & the other to battery 3. This gives a more even power draw off all three batteries & will extend the life of the batteries.
Yes. That is the configuration displayed in the 12V side of life link too. That is the configuration Winnebago uses in their coaches that require 12V batteries.
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Old 05-16-2014, 06:28 AM   #11
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Here is t the diagram from The 12 Volt Side of Life and it shows that positive and negative are attached to battery one and equal sized jumpers to battery 2 and then from 2 to battery 3.
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Old 05-16-2014, 06:46 AM   #12
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Okay, electrical engineering professor here.

If you use high quality, heavy gauge cables with good solid connections, it won't matter. There shouldn't be enough of a voltage drop in the cables or connections to cause a problem. I might consider connecting the house cables to the middle battery only from a reliability standpoint. If the connection between battery #1 and battery #2 becomes corroded or broken, two batteries are taken out, rather than one. On the other hand, if connecting the house cables to the middle battery stretches those cables too much, that could cause a failure.

In short, the way you have them is fine. Watch for corrosion in the connections. If you suspect trouble, disconnect all batteries and measure the voltage of each one individually. They should all be the same, or really close to the same voltage. If one is higher or lower, get your batteries tested and replace the connection cables.
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Old 05-16-2014, 08:31 AM   #13
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Originally Posted by LPD218 View Post
Is there any problem with this setup?

Is there any difference if I were to move one of the connecting cables to the farthest battery? I have seen them both ways.
To both questions: NO, No problem and unless you have a whomping big inverter (Even if you do) no noticable diference.

Some folks worry about "Balancing" the load between batteries but with say 8GA wire to the fuse panel and 4GA between the batteries (4ga cables can be picked up cheep, with lugs, at any auto store, standard starter/battery cable) balancing is highly overrated.

With 0000 to an inverter.. Well then it's a bit more important.
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Old 05-16-2014, 08:40 AM   #14
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Thanks for all the information. I saw the picture and that was why I questioned my setup. The parallel connection to the house was off the last battery and the serial shows connection off the first and last. I understand the need on the serial but didn't know if I was loosing some benefit by not doing my batteries in parallel the same way.

I will check my cables to see if I can move them to the middle battery just for my own sake of mind.

Thanks for the great answers!
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