My first time venturing into an off-grid power install and I am in the planning phase of this installation for my RV. The diagram shows my plan to install a Victron MultiPlus II 2x120V inverter along with the Cerbo GX. I may start with 2 LiFePO4 batteries and later go to 4 unless there is a compelling reason to acquire all 4 at the same time. The converter will be compatible with all battery types, including LiFePO4. My input is either shore power or a generator, but not both, so I did not include an ATS. For the shore power most, but not all sites will provide 50A but I should get 30A when 50 is not available. The DC side will be 12V since I have various 12V appliances in the RV.
Solar is a future plan and not currently included.
Feel free to make recommendations or point out improvements for this design. I hope to learn and share with others.
You say you are 12V with up to 4 12V batteries in parallel but have drawn them in series to give 48V.
What is the converter for, to give a stabilised 12V supply.
The negative of the converter is wrongly connected, it needs to go to the 12V negative bus bar so that the SmartShunt will measure the current going to the loads.
When you add solar the negative from the MPPT MUST also go the the negative bus bar.
Read the Multiplus 2 manual for required wire gauge, 6 gauge is much too thin. This also applies to the cable between the bus bars, shunt, isolator and batteries. If you follow the recommended twin cables to the inverter, then single cables of the same gauge go to each of the 2 initial batteries.
You have not shown fuses, do not forget them. The bus bars will need to be circa 500A rated to deal with the Multiplus load.
My bad - I followed a 48V design and forgot to swap the connectors on the batteries. I updated my design for the future.
The converter is to charge the batteries when connected to shore power. I don’t want to run the converter when I convert 12V to 120V via the inverter so I think I may need to turn it off unless there is a better way or charging batteries.
I fixed the wiring of the converter to go to the negative bus bar and will make note to also connect the MPPT to the bus bar when I get to Solar. I also added fuses .
I am glad to hear 6 gauge is too thin before I discover that by heating them up or worse. Upgrading to the correct gauge now.
Hi Leon, do you have an updated diagram? If so, I am happy to take a look at it for you.
I recently upgraded my RV (Thor Ace 30.1) to all victron equipment, so I understand a few of the nuances. I’m in the UK so I also had to convert to 240v as well.
Depending upon what factory equipment you have to connect you house and chassis batteries together for either bidirectional charging or emergency starting, you might want to consider an Orion XS dc/dc converter to charge your house batteries when on the move? Note this will require alterations to the factory design but it appears you are already on that path.
Note, depending on what battery technology you are adopting for your house battery, you may need to take care ref isolating the house and chassis batteries i.e. they may have different charge or even nominal voltage characteristics. The Orion does this job perfectly where as factory equipment used in many RVs i.e. BIM160 & 225s do not.
I’m more than happy to try to help.
Ref cable sizing, bigger is better (within reason of course) over stressed cabling gets mighty hot very quickly.
Leon, just a thought ref having the Converter (which is essentially a charger and PSU combined) only work when you are on shore power. A simple fix would be to move its ac supply from the main ac distribution board (which will receive inverted power once your installation is in situ) to the ac input side of the inverter. Obviously you’ll need a suitable breaker for the circuit but that would solve your problem of using inverted power to charge the batteries.
Note the Multiplus will obviously charge your house battery when you are connected to a shore supply
Assuming you main distribution panel is a combined AC and DC unit i.e. 120v breakers and 12v fuses in one enclosure, you’ll need a fused supply from your busbars to the distribution panel. I fitted a battery protect in this circuit so that I cannot over discharge the battery. Your BMS in the battery probably does this however.
I’d be inclined to keep the converter as a backup so long as it’s charge profile is compatible with your batteries (they are usually rudimentary and designed for lead acid thus compare with the LifePo charge characteristics of your batteries). That way if you have ac and had a problem with your battery or multiplus, you still have 12v thus lighting and essentials. Feed it from the ac input side of the of the multiplus and feed the dc output either onto the distribution board (which is no doubt where it is wired now) or the busbar. They are essentially the same but be careful if you use a battery protect as they don’t allow reverse current flow thus fit the battery protect near the distribution board and feed the board through the battery protect.
@ludo you have a good point with bmv712. I was considering the Victron Touch monitor since it will be easier for my wife to also see the status without scrolling through the options. I will keep bmv712 in mind as an option and it will be a less expensive route. Thanks for pointing that out.
Remote connectivity is a requirement for me thus I opted for the Cerbo GX and touch 70. Plus if it’s an RV you can display all your tank info if your senders are compatible.
Great suggestions, I do like the option of still being able to charge the battery without the Inverter and definitely a great idea to connect it to the AC side of the inverter. Then it only works when I need it. I will also look into the dc-to-dc charging option.
My RV is a 5th Wheel, so the option to monitor tanks is a plus. So much more to consider. Where do you stop - indeed!
The emergency battery start wiring looks a little complicated simply because I’m using NMC house batteries which cannot be charged with a Lead Acid charge profile thus I designed in a robust fail safe.
But there may be other elements of my design that will be common with yours and might be of use.
Weight is an issue for my outfit thus my Inverter will come later once I’ve done some other weight saving mods but the diagram shows you where to fit a battery protect if you consider it useful.
I made a few modifications based on all the discussions today which will ensure I get the right equipment the first time. Looking at your diagram I now have more to consider.
Please note that you’re still vastly undersized on your DC wiring - you’ll need around 4/0AWG (0000AWG) from your batteries to your shunt and busbars and from there to the MultiPlus (not 4AWG) and probably around 1/0AWG for your battery interconnects. You can work out the math on it (or work with your experienced DC systems installer) to narrow that down, but the 4AWG you’re showing is right out - maybe that was just a typo?
- I followed a 48V design and forgot to swap the connectors on the batteries. I updated my design for the future.
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