question

mfred68 avatar image
mfred68 asked

2x 50mm battery cables

I have a Multiplus 2, 48/10000 and according to the hand book that came with it, I should use 2x 50mm battery cables if under 5m. Thats two positive and two negative in parallel.

The multiplus does have two terminals on each + and - (4 in total) so connecting two red and two black wires is easy, but i'm a bit stuck as to how to connect the other ends of the cables.

I need to add an inline mega fuse to the positive wires but the fuse holder only has one terminal, same goes for the isolation switch, it only has 1 terminal.

So do i stack the two wires onto the single terminals, or do i need another busbar after the fuse and switch?

Or to simplify things should i fit a 70mm or 95mm single cable instead? The maximum length would be 1m per cable. (i'm still in planning stage, so nothing is fitted yet)

Multiplus-II
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2 Answers
max-payne avatar image
max-payne answered ·

Victron has a seperate guide about cabling.
https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf

It entirely depends on what you do with your system. I use 16mm2 for a 5000 with 50a max and it works fine with a low vdrop since the cable runs are short.

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nickdb avatar image nickdb ♦♦ commented ·
The requirements for a 5k state recommended fusing is 200A and 70mm cables for short runs.

50A is hopelessly underspec for that inverter.

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wilm avatar image wilm nickdb ♦♦ commented ·
Look at the industrial specs, not only at Victron specs. A 25mm² cable is capable 118A permanentely. So a MP 5000 draws less than 118A at 51,2V.


My 3kMP is connected with a 25mm² and there is are no hot cabels during exessive consumption. My thermal-camera shows less than 2°C after 10 mins.

FYI, the maximum cablelength is less than 50cm, so less than 1.5ft


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Craig Chamberlain avatar image Craig Chamberlain nickdb ♦♦ commented ·
I think you guys are talking about different things. @Max Payne seems to be talking about the AC cabling and @nickdb is talking about DC cabling. For an MP-2 5000, 50A is the correct MCB breaker rating for the AC side and 16mm2 cable would be fine. I use 10mm2 cable myself since the MP-2 spec says 13mm2 is the max cable size which I think comes from it being 6AWG, and 10mm2 is rated well above 50A dependent on reference method used.

On the DC side, for an MP-2 5000, 70mm2 is the correct size for up to (IIRC) 5m and I think it's 95mm2 after that, with a 200A fuse. But the OP was talking about the 10kVA MP-2 so not relevant here anyway.

I just wanted to point out why I think @nickdb and @Max Payne seemed to be in disagreement. :)

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daza avatar image
daza answered ·

@mfred68 Me personally I would use fuse breaker https://www.bimblesolar.com/extras/dc-fuse-disconnect?product_id=1898 victron says it’s 400amps assuming it’s 200amps per cable https://www.victronenergy.com/upload/documents/MultiPlus-II_230V/32424-MultiPlus-II___Quattro-II_120V-230V-pdf-en.pdf then bus bar 1000amp plus more amps it can take the better then maybe connected to Lynx power or distribution for battery connections just a thought all the best with system design mate

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