Is my MultiPlus II setup safe ? What else should i buy to prepare installation?

DIY
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Hello everyone.

I am looking to setup my Victron system. No Solar Panels for now, only ongrid Multiplus with battery (no export to grid). I have the following:

I am an IT guy, not electrician. I asked Claude about a workable setup but I am a bit worried by what it is saying as it looks like I have things missing:

https://claude.ai/public/artifacts/e803eb9c-fc0b-4492-8c76-0070db6b2c57

According to Claude I should also buy:

  • Class-T fuses 400A DC-rated (I thought Lynx Power In was enough)
  • Pre-charge kit: I never heard about this one but it looks like it’s very important ? AI claimed without it we can damage Lynx or Multiplus.
  • Breakers: I imagine those on the list are good.
  • Earth bar DIN rail: I don’t have one, I imagine it’s also needed.
  • Earth rod + clamp: How much for my system ?
  • Hydraulic cable crimper 16–150mm²: I didn’t knew I needed this. I imagine I need it if all cables aren’t premade. I don’t have all cables. I may invest in one if I can save on cables.

On AC side ofc a real electrician is gonna do the installation but I need to figure out everything on DC side myself. No Cerbo because I have my own servers.

Thanks for your support

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Lord please don’t use AI to try to figure out how to build your electrical system. LLM’s don’t know anything. I mean, literally, they don’t know anything at all.

Start reading, start studying. Victron’s “Wiring Unlimited” book (which is free, you can download it in pdf from the main page or read it online in html5) is a great place to start, but seriously, for your own safety, you need to understand what you’re doing if you’re going to be doing it, not just following what some LLM thinks is the most likely series of next words based on a prompt you gave it. Otherwise, please consult a reputable and experienced human DC and AC systems installer to work with you in designing a functional and safe system.

I know you say that you’ll consult an electrician on the AC side, which is good, but please understand that direct current is vastly more dangerous than alternating current. Please for the sake of your life and property -and that of those around you- either dedicate the time to learn the physics, pitfalls, and best practices of this work yourself, or consult with a professional who has.

That said: The Lynx Power In Class T does not come with fuses. You do still need to buy fuses for it.

Pre-charging the system is highly advisable, yes.

Components don’t come with power cables, so you would need cables and lugs and crimper and heat shrink if you were going to do this yourself, yes.

Earth rods, breakers, and a whole lot of other requirements will be largely dependent on your local governing codes and regulations, and your experienced systems installer should be able to assist with that, or possibly your authorized Victron distributor depending on their level of experience, expertise, and services offered.

4 Likes
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Thank you Justin. Indeed I know how LLMs are far from being magic and can also hallucinate badly, meanwhile electricity is very Dangerous. I am in a remote place. In my country Victron is very uncommon I had to import everything from the USA.

I am taking my time to learn but for safety reasons I was not feeling okay doing any wiring without showing my final planned setup to a human that knows about that.

Indeed I won’t touch AC at all as it’s electrician job. I will look at your resources and come back with a bettee understanding and make sure I can buy what’s missing.

Good to know for pre-charging, actually I cannot remember it from Multiplus manual but I imagine it’s there

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:+1:

@Purshing

You must read, read, read, have a look to the Victron online courses, talk with a good electrican about your project, talk with a local Victron reseller or specialist and THEN you can start building your system.

I have build my Victron ESS last year. I was thinking a lot about what I want, what is possible, then was reading, reading, reading the great Victron documentations, had a look to Victron online courses, start building, let an electrican check all before starting the system and then fired up the system.

I was also an IT guy like you in my professional life, but have also learned other skills before (study of physics and learned many other things). Without all these fundamentals, I would never have dared to plan, build, and put into operation a Victron ESS.

Electrical energy is a wonderful invention in our modern lives, but it can be very dangerous or even fatal if used improperly.

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The power in comes empty, so yes you need actual fuses to put in it. 400A is a bit much, at 52V that would be 20kW, your MP will give up way before that. Victron recommends a 200A, but if you dont plan to use the overload capabilities of the MP, even 125A would be fine. Use the smallest fuse necessary, but still use 70mm2 cable for the full 200A.

One could argue that you can leave out the whole lynx, since the battery has a builtin DC breaker, so you could run the DC cables directly into the MP. But this would be a hinderance once you would install PV and try to add MPPTs.

Do you plan to switch the DC system on/off daily? Then yes, use a precharge resistor. Otherwise, if you once switch it on and leave it running like many of us do, dont bother. Also, the precharge kit requires access to the battery positive infront of the DC breaker, because you would need to precharge the inverter before closing the DC breaker. Or you leave out a fuse while precharging, but then you need to install the fuse while still holding the precharge. Possible, but not convenient.

As for the AC side, since you dont mention any plans on how to actually use the system, im going to assume ACin comes from your main breaker panel, and ACout goes to a new subpanel. Earthing can be used from the main panel, at least the MP housing needs to be earthed, DC negative can be, depending on your local regulations its also a must.

The cerbo can not be replaced by a server, since its main function in this case would be to enable communication between the battery and the MP. Otherwise you would need to rely on two-signal-BMS control which is a bit archaic at this point. It also enables charge/discharge control. If you use a plain MP, it will simply keep the batteries charged but apart from that cant feed back to mains for example

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Same I was thinking a lot last year. Issue is that buying the stuff, getting them by boat to Central America, Christmas madness and packages arriving slowly… it took more than 4 months to get everything and you would hardly believe I forgot a lot about what was even my initial plan when I opened my packages. Ofc it’s my first install ever otherwise this wouldn’t happen.

I did study electronics and physics that helped me even thought that was a long time ago.

I wouldn’t be against remote consulting as I know no Official Victron instalator would come where I am doing install. There’s only 2 in the capital I think. They didn’t had anything for more than a Van install I would say (lowest power inverter, barely any stock). As a result I bought everything besides the battery on CurrentConnected.

There’s not even a single Software Integrator in the whole region. With this first setup I would be able to touch IT side where I am good at and be part of that map

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I didn’t mentioned I have Victron MPPTs too but I am not gonna use them for now and if I remember well that is the reason why I bought the Lynx Power In.

Your assumption is right, that’s why I have a second, unused panel.

Thanks for your input.