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Old 12-03-2015, 03:25 PM   #1
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Battery Layout Over-Thinking Help Request

I can find series-parallel configurations all day long for 6V batteries. I have a square to work with as my space and have 4 12v batteries, I want to wire in parallel. Anyone have opinion on the arrangement of the cells for short connections?

I don't know if there is a right or wrong answer here. I attached a few of the ideas I've had.
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Old 12-03-2015, 04:27 PM   #2
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Depending on your wire size, it may not matter much. The idea is to equalize the voltage drop from the charge/discharge connection point to all four batteries for each of the plus and minus connections while simultaneously minimizing the total drop. If there were a way to put a connection in the middle of the long jumpers on your bottom option, that's the one I'd go with. You could also leave off the long jumpers and run eight separate, equal jumpers from both positives and both negatives to your distribution buss.

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Old 12-03-2015, 04:28 PM   #3
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Here's a test for the design to keep all the batteries even. From the common positive all the way to the common ground, each battery should have exactly the same length of wire and the same number of connections. Your first example is poor since the bottom two batteries have more wire and more connections than the top two. The second example favors the bottom right battery.

It is important to keep them balanced for even loading and charging.
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Old 12-03-2015, 04:38 PM   #4
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The best of your examples is the top right if you move the final positive load line from the bottom right battery to the top right battery. Think of a row of batteries with one main connection left to right and the other right to left. Then rearrange then "fold" line of batteries.
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Old 12-03-2015, 05:33 PM   #5
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What wanderer said. I didn't pick up on your load lines.

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Old 12-03-2015, 05:46 PM   #6
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Cut the red wire, no cut the blue wire, did I say blue wire? I meant cut the red wire! No, cut the blue wire! I definitely said red wire!
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Old 12-03-2015, 06:53 PM   #7
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I am only injecting a comment, as I have no experience with the LI batteries you are installing, but don't they have an internal voltage regulating system which may make the problem less of an issue than it is with Lead Acid batteries. Just a thing to possibly consider
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Old 12-03-2015, 08:22 PM   #8
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They do and I'm using copper connectors, I was just trying to figure out what would be the best layout/cleanest install approach since I'm not putting them in a row. Becuase my sense boards are prewired I can't do a block like I intended.

You can see here how I intended to lay them out and where the pos and neg terminals would be.



But what I don't want to do is re-solder 18 sense boards into my configuration, and they're pre-wired neg-pos-pos-neg-neg-pos etc, kind of annoying, and I totally missed it until half way into my project.



I mean I could, but dang, I'd be at that all day, so I arranged them back into 12v cells.
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Old 12-03-2015, 09:10 PM   #9
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I would leave the 12v blocks for convenience. Do you get to choose whether positive is on the left or right? Your diagrams should both battery polarities.
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Old 12-03-2015, 09:26 PM   #10
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Here is a layout with all the same battery polarities. Each battery has 3 interconnecting links in the circuit -- not counting the main lines which are obviously the same for all.
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Old 12-03-2015, 09:32 PM   #11
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Quote:
Originally Posted by Wanderer2604 View Post
I would leave the 12v blocks for convenience. Do you get to choose whether positive is on the left or right? Your diagrams should both battery polarities.
I can choose. Here is a better top down view. Each cell is 3.2 volts and then combined into a 12v block of 4 cells.



The problem I was having, is that the sense boards require me to leave them in the "from factory" position. Which left me wondering where to stick the leads.
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Old 12-03-2015, 09:37 PM   #12
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This layout uses less cable and has only two interconnects for each battery circuit.
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Old 12-03-2015, 09:48 PM   #13
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Here's the list of links per battery.
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Old 12-03-2015, 11:21 PM   #14
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Good idea, think I'll use that. Now if my 4/0 AWG and lugs show up tomorrow I can finally get started. Last piece of the puzzle that hasn't come in the mail yet.
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