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alaskannoob avatar image
alaskannoob asked

Recommended DC Fuse/Cable Size for Multiplus II 48/15000 (not shown in manual)

Section 4.2 "Connection of Battery Cables" does not show information for the 48/15000 version. Does anybody know what the DC fuse size is and the recommended cable sizes are?

Multiplus-II
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Doing some math on your own you get to a 600A fuse, at last 2x70mm² for 5m and 2x95mm² vor 10m.

Or looking at the manual of the "old" 15kVA Quattro:
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1677174844124.png (38.3 KiB)
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alaskannoob avatar image alaskannoob commented ·

Thanks, I appreciate that info. It would be cool if, while you're having Victron fix its manual's discussion of parallel capability, it were to add a section for the 15K in the table in the manual for battery and fuse sizing too. For people like me who live in places that don't have solar installers or other people nearby.


As a guy re-designing my system and my cable selection and my circuit breaker selection at the last hour, after spending a ton of money (because a Victron dealer wrongly told me the 48/8000 units would operate in parallel) and who is now scrambling to find an option to save the massive investment I have already made in Victron equipment (while also trying to figure out what to do with two brand new 48/8000s that the dealer sees no reason he should be involved in being returned), it would be nice if the manuals were more complete. So that I don't burn down the forest at the end of this adventure.

Given that the 48/15000 can take a peak of 27000 watts, that means I have to find cabling that can handle 563 amps and associated circuit breakers. And before I spend all the money on breakers, and cables, yet again.......it would be nice to know they will fit in there.

So I appreciate the help. I just wish it were in the manual to begin with.

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alaskannoob avatar image alaskannoob alaskannoob commented ·

I think I will go with 2 x 250MCM cables that can each handle 461 amp at 40C. The cable has .875" finished outside diameter and I'll plan on using four of them (two positive and two negative) to connect this giant inverter. I sure hope those wires fit and that this clever idea of not using cable diameter and instead using cross section doesn't hose me in conversion after I wield this 180 pound beast up to be worked on. Now I need to find the circuit breakers.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ alaskannoob commented ·
I already forwarded it and it will be added, but it will take a few days.
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ppbering avatar image ppbering Matthias Lange - DE ♦ commented ·
Hello,

I've found this topic and it seems that it's still not updated in the technical documentation.

A multiplus II 48/15000 is currently under installation in my house and the dealer has used a 50mm² for the connections (and a 300A fuse).

Isn't that a bit dangerous given the fact that I planned on using 2 15.4kWh byd LVL batteries for the DC source ?

Can you confirm that it must be at least a 2x70mm² (it's under 5m, around 1m and half).


Thanks.

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Alexandra avatar image Alexandra ♦ ppbering commented ·

The BYD 15.4 kwh have 250A output. They have a recommendation for the max cable size for the batteries.

Any decent electrician will be able to work out DC cable size and fusing without a manual.

15000 ÷ 48 is 312.5 A

300A current ability for most fine strand battery cable size will be about 100mm² cable so 2 x 50mm² will work. (That is what is recommened for the 10kVa so it seems logical/reasonable to go larger)

To be honest though with the inductor in the Multiplus 2 inverters I would go as big as it can take the system will just be more efficient as there is less cable resistance and then there will be less heat loss etc.

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ppbering avatar image ppbering Alexandra ♦ commented ·

Thank you for your answer.

It loks like my system will not be able to push more than 63Ax230V => 14490W.

So it looks like it would have been a better idea to put bigger than 50mm² but that was not what they put on the quote. So I've got to live with it (and given that I'm not equipped at all for changing the cables, they will stay there for the best, or the worse - hope it will be OK).

@Matthias Lange - DE are you still on the subject for the documents update or do we have to ask someone else (no problem if so, I totally understand that sometimes you are asked to deal with other things that the one you treated initially :D)

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johnsmith avatar image
johnsmith answered ·

Still not added

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