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Pantelis Zirinis avatar image
Pantelis Zirinis asked

Parallel Multiplus Lynx Distributor. How To Fuse?

Hello Victron Community and Happy New Year,


I am thinking of updating my Victron setup and adding a second multiplus. At the moment I have a Multiplus 12/3000/120-50 on my system and I am looking at getting an identical one to increase the power so I can run more ac devices. The battery bank is a 12v 702Ah, that contains 16 Lifepo4 Cells. I might be adding an extra 4-8 cells to it in the future.


I am thinking of connecting my battery to a Lynx Distributor and from there connecting the 2 Multiplus and other loads/chargers on my system. Cable lengths will be kept to the minimum and should not exceed 1 meter (battery to lynx and lynx to each Multiplus).


My concern is that as mentioned on the Multiplus manual, the device has to be fused by a Class T fuse and the Lynx is using Mega fuses. I have seen multiple installation where a Class T fuse has not been used, but I am concerned on not following the recommended way.


The next problem I am facing is cable sizing. 2 x 400A = 800A. I need a cable that is large than 120mm2 or 4/0AWG, which is super hard to find and a lot harder to work with.


Has anyone managed to find a solution using a Lynx Distribution system? The system can take the load as it is rated at 1000A, but it cannot take Class T fuses.


I was thinking of adding an 600-800A fuse on the battery side and the connecting to the Lynx Distribution. An alternative could be two cables, each fused with 400A Class T fuse. But then having more fuses on the lynx will increase resistance.


Any ideas or recommendations are welcome.

I am attaching the diagram of my current system for reference.

Pavan Guru DC Electrical Diagram.pdf

multiplus in parallel
pavan-guru-dc-electrical-diagram.pdf (12.3 MiB)
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2 Answers
brucevanderbilt avatar image
brucevanderbilt answered ·

I've seen a few installations with parallel Class T fuses for the entire bank. https://www.youtube.com/watch?v=UHlUXwrCGKg.. Is there any reason this wouldn't work?

There's plenty of online debate about parallel fuses. But the long and short always results in a thread conclusion that paralleling fuses is acceptable and commonly done by professional electrical engineers in electronics. The result is a doubling of the fuse rating. (e.g. two 400a class T fuses, would equals 800a protection).

However, it requires the use of identical fuses, holders, wire lengths and cross sections, and fittings. Granted there may be a very slight actual variation in actual protection if there are slightly different resistances between cables/fittings to each fuse.

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Pantelis Zirinis avatar image Pantelis Zirinis commented ·

The video has a very similar setup to the one I am having and he has done the fuses in a similar way I was considering doing it.


Parallel fuses are not ideal, as each cable needs to be individually protected. So I am also considering of having one fuse for each inverter and another fuse for everything else. All of them class t (so they protect the surge that the battery can produce) and as close as possible to the battery, so there are no unprotected long runs.


Also quickly looking into the video the cable that comes from the batteries does not look big enough and does not look fused. I could be wrong as I cannot see what happens on the battery side.


I will drop them (the video creator) a message and see if they had any challenges. It is always nice to see that someone has done what you are planning and how it worked for them.


At the moment I am postponing this project to do some more research and see if I can upgrade to a 24v or 48v system, which will simplify the wiring and fuses a lot. And provide some space for future upgrades.


Thank you very much for that.

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seb71 avatar image
seb71 answered ·

You are pushing it somewhat too far for a 12V system.

If you still want to do it, make some busbars from copper bars (DIY) and use NH HRC fuses (in dedicated NH fuse folders).

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Pantelis Zirinis avatar image Pantelis Zirinis commented ·
I am not familiar with the NH HRC fuses. I was thinking of the custom busbar option and 3 x class t fuses (2 for the inverters and another for the rest). I suppose you propose a similar setup and not a single 800A NH HRC and then the Lynx?


Why are you recommending the NH HRC compared to Class T? Bear in mind that I already have 2 Class T Fuses on my system, so I could add a custom busbar that can accommodate a third one.


On the other hand I agree on the pushing it too much for a 12v system. I have not placed the inverter order yet, as I am considering going to 24v. Problem is that everything on the boat is 12v, so it will be adding another complication to the system and a much higher expenses to change the current inverter.

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