MultiPlus 12/3000/120 Battery Cable & Fuse Size

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pieter asked Mar 29, '19

MultiPlus 12/3000/120 Battery Cable & Fuse Size

I am planning to install MultiPlus 12/3000/120. The unit does not come with battery cables or battery protection fuse. What cross sectional area of battery cable is required to connect batteries. The distance will not be more that 2 meters. What rating fuse is required. (Batteries 2 x 220Ah)

The manual states 2x50mm positive cables and 2x50mm negative cables doubled up and a protection fuse of 400A. (Victron supplier wants to supply 35mm cable)

Not sure is manual is correct because when you purchase a MultiPlus Compact 12/1600/70-16 230V there is 1.5m of battery cables supplied but only 35mm and manual states it should be 70mm. Just a bit confusing.

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Answer 1 · 2019-03-29T20:35:37Z

Murray van Graan answered · Mar 29, 2019 at 08:35 PM

I agree with the manual. Being a 12v unit the current draw from the battery at full load will be in the region of 200 to 250Adc depending on the battery voltage. Since the unit can support a surge of double that the 400A fuse seems to be correct too.

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JohnC ♦ commented · Mar 30, 2019 at 02:05 AM

I once used a competitor's 12/3000 and it too specced 70mm2 wire and 400A fuse. That worked fine, but the inverter didn't.

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Answer 2 · 2020-08-11T15:18:41Z

ericrrmorin answered · Aug 11, 2020 at 03:18 PM

I am running into this now as i install a 12/3000. I thought 400A is too large of a fuse for 1/0AWG or 50mm. I also thought that this is a ABYC no-no to double up on conductors with a fuse that is too large to protect individual conductors. I would think the way to go here is 2x 1/0 AWG (50mm) each with a 200A fuse?

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wkuna commented · Oct 08, 2021 at 01:56 PM

Very late to this post, but I had the exact same thought as @ericrrmorin. No way you can safely use a 400A fuse with Victron cable size recommendation. Unless I'm missing something.

If I interpret the ABYC standard correctly, the only setup that would comply with the 400A fuse requirement is to use 4/0 cables, as it is also suggested on this blog post: https://www.victronenergy.com/blog/2020/10/30/how-to-install-a-multiplus-inverter-charger/..

On the other hand, if the output peak power of the Multi is 6kW, at 0.93% efficiency, this means a peak current of 537A, lower than the allowed amperage on a 4/0, and barely enough on 2 1/0 cables.

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