New Install - System Review Request

DIY
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Newbie here just getting into the Victron world. I have pieced together a new system for my RV and looking for input into my design before I start installing. It is all sitting in my garage right now, powered on with a couple of DC power supplies and connected via VRM and everything is update to date. Going to hook up the batteries and start final testing this week and hopefully install this weekend, weather permitting.

Here are the particulars:

Existing design:

2022 Riverstone Legacy 42FSKG fifth wheel

2x 100ah Go Power LFP

Go Power Weekender 570w solar package (3x190w panels parallel, 30-amp PWM non-bt SCC)

Go Power 1500w inverter with Transfer Switch

PD-9380v converter/charger

WFCO 8930/50 PDC (not split phase, just 120v x 2 design)

Firefly Integrations system running house, hvac, water pumps, etc.

Onan 5500 LP generator

WFCO T-57r ATS

Progressive EMS50-HW power protection on shore power input

What I have bought:

Multiplus II 12v/3000va/2x120v

MPPT 100/50 SCC

Lynx Power In, Shunt, Distributor

Cerbo GX MK2

1-off-2 Manual Transfer Switch

2x Wattcycle 12v 314ah Smart Minis, each one into Power In separately

Several breakers, cabling, lugs, etc. needed

What I am removing and changing:

Remove PD-9380v converter

Remove Go Power Inverter

Remove Go Power SCC

Remove Gp Power 100ah batteries

Convert solar panels from 3P to 3S configuration

I have attached a rough diagram showing the desired build. I have some other things that I will seek input on, but my primary concern is the basic system diagram right now. I am installed a manual transfer switch so that I can bypass the MP2 if needed while on shore power or generator. It will fed by the ATS output on input 1, middle position is off, and from the MP2 AC out 1 into input 2 (primary position). My RV disconnect switch feeds the PDC and the firefly system (4 wires into the disconnect switch) and I will be leaving that as well as the non-switched loads like the hydraulic pumps for levels & slides and the disc brakes, generator start circuit, safety equipment in place mostly as is for now. I will leave the inverter in place for now but disconnect it from all power. I will pull the 20amp AC breaker that feeds the converter out and replace with a 15 amp breaker and connect the inverter fed circuit from the new 15amp breaker. With my original inverter only certain outlets and the residential fridge ran from the inverter, but now the whole trailer could run from the batteries now up to the MP2 output limit.

All of the wiring I have is labeled on the diagram and is 105 degree C welding cable. Each battery connects to the Lynx Power In via 350amp class T fuse and 250amp breaker/disconnect via 2/0AWG. The MP2 connects to the Lynx Distributor with a 400amp MEGA fuse via 4/0 AWG. The Lynx Shunt has a 500amp MEGA fuse installed and is the main breaker for my system. The Distributor will be grounded to the RV frame via 4/0AWG to a new ground location with 3/8” zinc bolt tapped into the frame directly. I will also connect the always on DC loads, the generator start circuit, and the MPPT 100/50 SCC to the Distributor, so it will be full.

I feel like that is a wall of text, but I am very appreciative if anyone can help me debug the logic and make sure it all makes sense. I am happy to include more details if it is helpful, but I think the diagram has most of it now. Thanks for reading and looking!

In the diagram, the reddish arrows note AC power, white is DC.

RV 12v MultiPlus Layout.drawio
RV 12v MultiPlus Layout.drawio841Ă—800 47.9 KB

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Generator stuff:

My Onan puts out 2 120v circuits, one breakered at 30amps, the other at 20amps. I wll be joining these at the ATS to where I have 1 hot and 1 neutral coming in at 50amps. This will allow me to use the full power of the generator across the entire PDC and not have to worry that half is only served by 20amps. I can also use Power Assist from the MP2 to help with surge loads like ACs starting (may be able to run all 3 on generator if necessary while I have battery power).

One thing I have identified is that the Firefly will only see 120v coming in to it (it monitors AC feed) because it is actually 2x120v not split phase 240v. Therefore, it will default to 30amp and shed loads automatically. This has a somewhat creative fix I am still reading about.

Essentially, I need to trick the Firefly system into believing the generator is running when I am inverting with the MP2. It will think it is getting 50amps of 120v power from the generator when it is actually getting ~30amps of inverter power. I will need to manage the load myself, but it will cover the load and 1 AC/HP (3 ACs, 2 with HP). To do this, I will be using a relay from the MP2 to put +12v on the GEN RUN input wire for the firefly. The generator will tell the Firefly when it is running, and the MP2 will tell the Firefly the generator is running (it is not running) when it is inverting. I do not have AGS enabled currently and do not plan to use it. I am considering adding generator control to the Cerbo as well. Has anyone here done this specifically and have any thoughts or pointers?

I am going to flush mount a 7” touchscreen right above my Firefly Tablet in the cabinet for the Cerbo GX display. I fished the wall for the USB and HDMI cables, so I just have to make a mount and a bezel for it, but it is not a priority as I have VRM working already.

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Just bumping to see if anyone has any input here. I am hoping to start the work in the RV this weekend.

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I don’t do installation or system design, leaving that to professional installers, but one thing I will note is that this ^^ may not work; most aftermarket touchscreens use the USB for carrying touch instances back to the receiver, which the Cerbo and GX Touch do not. Your aftermarket screen will almost certainly display, but there’s a very high likelihood that the touch will not work - that’s why there is specifically a GX Touch 50 and GX Touch 70 designed to work with the Cerbo.

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I appreciate the comment, thank you! Based on research, others have indicated this one works well (display and touch) and was a fraction of the cost. I don’t intend to use it often as I have a tablet in the RV already for controlling the firefly system, so I can just use that for a remote display. So not a big loss if that part doesn’t work out.

ETA: I will test it out soon and find out, but will likely not reply back on that given this is a Victron forum and I don’t want to be that person ;).

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