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Old 07-18-2016, 07:38 AM   #21
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IMHO, the better way to connect two 12v batteries in parallel is with a selector/parallel/cut-off switch. You eliminate the parasitic drain of the weaker battery by not having them both always hooked in parallel, you can drain one and still have fresh one, or if needed, connect them both. Recharge times are slightly better too.
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Old 07-18-2016, 08:12 AM   #22
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From everything I have read about batteries the first figure is the right one. Look at 12 volt side of life website. Anyway it's the way I hook up my batteries. I have two separate banks of batteries, four six volt batteries each.


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Old 07-18-2016, 08:29 AM   #23
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While there "may" be a negligible difference between the two connection diagrams, the first is correct. It's not just the cable, it's connections as well. After 6 months to a year with significant loads and recharge cycles, the second battery in scheme #2 will have "loafed" and will be in a different state of charge and lifetime than the first. Equal line lengths is pretty simple to achieve...why argue about it?
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Old 07-18-2016, 08:43 AM   #24
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This discussion is making me crazy! If you look this up on any battery seller's website, or battery manufacturer's website, or take an electrical seminar with Gary Bunzer, you will see that the second illustration is the right one.

In the first one, the connecting wires create additional resistance to current flow, making the second battery work harder than the first. Why would you want to stress one battery more than the other?
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Old 07-18-2016, 09:02 AM   #25
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You are correct. Lacking numbers on the attached thumbnails (i.e. who's on first?"), the connection layout where the positive goes to one battery and the negative goes to the other is correct!!!!
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Old 07-18-2016, 09:17 AM   #26
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I'd like to see the meter you guys are using to read the difference from one end of an 8" long piece of battery cable to the other.

If everyone is so worried about the connections, resistance, current flow, loafing batteries, or another working harder in a parallel set-up, why even connect the two together.
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Old 07-18-2016, 09:28 AM   #27
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Will you ever notice? Nope.
Agreed. Unless we're talking about large banks, which most people don't have, it's negligible. Doesn't matter. It's all academic at that point and 95% of people will never notice a difference. You could probably put a banana peel (or half a coconut, and apple, and three bananas) two inches to the left of one of the batteries and counteract the impact of wiring them incorrectly in parallel.
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Old 07-18-2016, 10:15 AM   #28
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Probably true that it won't make much difference with small battery banks, but why deliberately do it the wrong way if you don't have to? In most things there is a right way and a wrong way. Not a whole lot of gray area here.
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Old 07-18-2016, 12:01 PM   #29
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X2...my thoughts exactly. It is just as easy to do it right...
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Old 07-18-2016, 01:36 PM   #30
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I was just pointing out that it's kind of a pointless argument. Both are "right". One may be more efficient than the other, but probably won't make a difference to the vast majority. Having said that, I wired mine for opposite corners when I was on 12V, so I'm not arguing, lol.
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Old 07-21-2016, 12:14 AM   #31
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x2 on everything that Phil said.

That is why the first responses were all voting for option #2. Phil even did a great job of explaining exactly why you want it wired that way: resistance in the wires balances out to each battery on option #2.
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Old 07-21-2016, 04:43 AM   #32
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With # 1 you'll get more current drop along the way and theoretically if you kept adding batteries in that series the last battery would have to do more of the work than the first.

With #2 you've essentially turned two batteries into one battery so all works together more equally and efficient.
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Old 07-21-2016, 07:17 AM   #33
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To each his own, I'm not trying to change anyone's mind but I'll keep wiring my batteries like option 1.


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Old 07-21-2016, 08:46 AM   #34
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To each his own, I'm not trying to change anyone's mind but I'll keep wiring my batteries like option 1.


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Agreed... The correct way.


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Old 07-21-2016, 09:55 AM   #35
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Agreed... The correct way.


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Really not the most efficient way for a balanced bank.
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Old 07-21-2016, 11:11 AM   #36
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Really not the most efficient way for a balanced bank.

So you say. I am not knocking the way you wire up your batteries, after all they are your batteries and besides they will work either way. My two banks of batteries are wired option one and next year when I go to a bigger bank they will be wired option one. Besides it doesn't matter to me what you think they are my batteries


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Old 07-21-2016, 11:19 AM   #37
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Do I really care. NO!

Just stating an accurate fact.
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Old 07-21-2016, 12:52 PM   #38
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Do I really care. NO!

Just stating an accurate fact.
Oh no, we can't have facts on the internet!

Some folks you just can't reach. So you get what we had here last week, which is the way he wants it. Well, he gets it. I don't like it any more than you folks.

Yup any way you wire up that gives 12V out will work. And you may not notice the difference between how whatever works and how the best setup works. But that does not change the data and the facts.
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Old 07-21-2016, 02:49 PM   #39
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12 V Battery Connection

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Originally Posted by boondocking View Post
Really not the most efficient way for a balanced bank.

Actually it is.


Go check out some large solar installations.

Even better. Look at some high current setups.
You will find we are correct.

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Old 07-21-2016, 03:01 PM   #40
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Nobody says to hook them up " battery boost" style.

Draw from opposite ends, equal length cable.


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