Busbar Copper Directly on Battery Terminal

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cory cantrell asked Feb 27, '21

Busbar Copper Directly on Battery Terminal

Hello - Looking for some clarification on batteries in parallel wiring using 110 stock copper of 1"w x 1/4" thick by proper length for clean terminal installation. I understand the cables need to be on opposite ends of the bank (Postive/Negative) as described in a diagonal use case. I will use heat shrink on each bar and have a piece of plexiglass over it for a nice visual and additional safety.

My question is what length of cables are needed to be matched? Is it the length of each copper bar on the positive + the length of the positive cable to the Lynx Power In has to be equal to each copper bar on the negative + the length of the negative cable to the Lynx Power in? Or is it just the Cables coming off the back and not the bars? Or something else?

Thank you.

battery charging Battery Balancer

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Answer 1 · 2021-02-27T15:27:26Z

seb71 answered · Feb 27, 2021 at 03:27 PM

I would not connect the batteries like that.

If you wire them like that, why even bother with a Lynx Power In?

Best way to wire batteries in parallel is to use busbars (like Lynx Power In or DIY) and to have all negative wires (battery negative terminal - negative busbar) the same length and all positive wires (battery positive terminal - positive busbar) the same length. With a fuse on each positive wire.

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cory cantrell commented · Feb 27, 2021 at 04:24 PM

Hi Seb,

Thanks for the comment! I for sure understand what you are saying, I just really like the look of the copper straight bars and also really hate the look of cable monsters...

If I did do it this way, or similar with bus bars between the battery terminals, what has to be the same length? Is it just the cable leaving the bank or the full distance between the bus pars and the cable need to be the same length?

In reading the "Victron Unlimited" guide they have this the below diagram and it looks like in option 3 (named halfway) the cables are not the same length. And same with option 1 (Diagonal). This is why I am trying to figure out what wires exactly have to be the same length. The full guide is here: https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf but to save you the long read :) This is the image I am referring too:

Thanks again man, hope we can continue this discussion!

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seb71 cory cantrell commented · Feb 27, 2021 at 04:52 PM

I would rule out options 1 and 3 just because you can't use an individual fuse for each battery (between the positive terminal and the common positive point).

I would rule out option 2 for more than 2 batteries in parallel, because I don't think it is a good idea to have many wire lugs on the same post/bolt.

So really only option 4 is viable for many batteries in parallel. But with fuses on each positive wire between each battery and the positive busbar.

I suppose you could bolt the negative busbar directly on the batteries negative terminals. But that would make removal of a single battery (if necessary) more difficult.

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Answer 2 · 2023-09-25T13:45:50Z

steadmane answered · Sep 25, 2023 at 01:45 PM

Corey, I was just about to post the same question when I saw your post. Can you comment on what you eventually did?

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pwfarnell commented · Sep 25, 2023 at 03:35 PM

I am not sure solid copper bars are a good idea because copper has a high coefficient of thermal expansion. This may stress the battery terminals. On lithium batteries where prismatic cells ate connected the interconnects tend to me made from say 5 layers of 1mm thick copper and they have an expansion hump in them.

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