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flyinggs46 avatar image
flyinggs46 asked

We are seeking to wire our Victron solar controllers to a bank of 4 Victron AGM batteries - I want to check how we should wire them

We have one challenge in that one of the batteries is on the starboard side of the engine and the other 3 are next to each other on the port. Reading some of the articles it sounds like this could create a problem due to different cable lengths between the bank's batteries. Is this a concern?


Is there a way around this issue or can it only be achieved by placing all the batteries next to each other and connecting them in parallel with the +ve feed at one end and the -ve feed at the other?

I assume the battery monitor should then be wired into the same feeds?

BMV Battery Monitor
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kevgermany avatar image kevgermany ♦♦ commented ·
Do you want a 12,24 or 48V system?

Looks like 12V, but...


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snoobler avatar image
snoobler answered ·

Yes, this is a concern. Parallel batteries in a bank should be wired with identical resistances. You could overcome this by additional conductors to the remote battery.

Example: you have cables of length 1 joining your 3 batteries, and you have cables of length 2 to your 4th battery. If you put a second set of cables to the 4th battery, the two length 2 cables in parallel would have the same resistance as a single length 1 cable.


You can confirm the effectiveness of this setup by using a clamp DC ammeter to measure current running through each battery under heavy load.


The battery monitor should be at the main (-) terminal (either battery 1 or 4 at your choice). All loads and chargers should be attached to the other side of the shunt.



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flyinggs46 avatar image
flyinggs46 answered ·

Thank you - can I ask - what happens is parallel batteries don't have the same connecting wire resistance?

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flyinggs46 avatar image
flyinggs46 answered ·

Thank you - sorry - mistyped - can I ask - what happens if parallel batteries don't have the same connecting wire resistance?


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klim8skeptic avatar image klim8skeptic ♦ commented ·

Some batteries get charged/discharged more, and fail sooner.

Wiring unlimited guide some info in section 3.

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sharpener answered ·

It's a bit more complicated, each battery should see the same resistance to the common connection point. So the bank of 3 batteries should have cable that is the same length as the single one and has 3 times the cross-sectional area. Otherwise the single battery will still do most of the work and be the first to fail.

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