I think it's time for a Multiplus

[corn18]

I have finished my first ever LiFePO4 with solar install on my 5th wheel thanks to all the help on here. Now that it's in, I am thinking about simplifying the setup with a Victron Multiplus II 12/3000/120x2. Some thoughts:

- I would keep it super simple and run 50A split phase (is that the right words for RV 50A power) shore power to AC in on MPII. Then run AC1 out to the main panel. I know I can't power everything on the inverter, but that's no different than when I am on a genset.

- I need a 50A split phase CB between the EMS and the MPII. How do I do that?

- I will initially be underpowered with only 2 x 206AH 12V SOK LFPs. I have seen 115A sustained output from these batteries, so I think adding a third battery should be enough.

Anything else I should be thinking about?

Current setup:



WIth Victron MPII:

 

[DIDDLYV]

just installed my multiplusII the documentation calls for 2 1/0 cables each for the positive and negative 12 volt DC feeds. I have no clue why but I did run the 2 1/0 cables. I wired a 150 amp fuse to the 1/0 feed from each battery plus. the put a heavy duty cut off switch on each lead to a bus bar then connected the multiplusII to the positive and negative busbars with the 2 1/0 cables. I used a total of 5 feet of 1/0 cable from each battery both positive and negative (each 2.5 ft from terminals to Multiplus terminals) to the multiplusII. I also jumped the cutoff switches with a 50 ohm 100 watt resistor and switch to perchance capacitors

 

[Short_Shot]

2x 1/0 60c cables can carry roughly as much current as a single 4/0 90c rated cable.

Why they'd spec two smaller ones is beyond me but it is a bit easier to deal with for the average user. Perhaps the terminals are not suitable for the physical size of a "typical" 4/0 lug?

 

[corn18]

I plan to just double up the 2/0 cable I have now. I have 2/0 running to both inverters that are currently installed so I will just reuse that. Looking at the pdf of the connections, I’m not sure if 4/0 would fit the lugs or not. If it would fit, I would prefer a single cable vs 2.

 

[Short_Shot]

I plan to just double up the 2/0 cable I have now. I have 2/0 running to both inverters that are currently installed so I will just reuse that. Looking at the pdf of the connections, I’m not sure if 4/0 would fit the lugs or not. If it would fit, I would prefer a single cable vs 2.

Id only add to keep in mind that 2x 2/0 is a lot more current handling than a single 4/0. In case you actually needed the double 2/0 for whatever reason, which I doubt is so.

Personally I think that if you already have the 2/0 and a single 2/0 is enough for the load you have it really can't hurt just to use what you have. Doubling that up is redundancy you'll probably never need but will definitely give you a really nice low resistance connection under load.

Just don't forget to fuse them both, or use one fuse that's below the single cable rating and I'd wager you'd get many years of good reliability from that connection.

As for the 50a split phase question, that is the case as you imagined. The 50a connectors should be 2 legs of 120 in the split phase config to provide the 240 split phase power you expect, plus neutral and earth ground.

I do know there are interesting safety concerns when wiring in both a generator and shore power connections and that neutral bonding safety comes into play here. That's a question I'd leave to an expert.

Regarding your other questions I'm sure someone will still come along.

Split and multi-phase (including intentionally grounded phases, that's a wild one) is an issue that I've got experience with using, but not creating.

 

[corn18]

I found a simple 2 space load center to hold a 50A 2 pole CB for shore power. So have that solved. The more I look at this setup, the more I like it. I wish I had just skipped right to the Victron. I had to buy a Progressive Dynamics Li capable converter charger ($300), a Xantrex 2000W inverter ($600), the remotes for the 2 inverters ($100) and the AC sub panel ($200). And all the wiring Changs for the sub panel. All I really needed was the MPII for $1550. Much more elegant system, too. Oh well. Live and learn.

 

[noenegdod]

2x 1/0 60c cables can carry roughly as much current as a single 4/0 90c rated cable.

Why they'd spec two smaller ones is beyond me but it is a bit easier to deal with for the average user. Perhaps the terminals are not suitable for the physical size of a "typical" 4/0 lug?

2x the lug contact surface area at the connection?

 

[Short_Shot]

2x the lug contact surface area at the connection?

?

No I mean the cables themselves.

 

[noenegdod]

?

No I mean the cables themselves.

I understand that you were talking about the cables, but perhaps the reason they spec 2 smaller cables instead of one larger cable is because of the fact that now there is 2 lugs making contact, increasing the surface area for that connection, reducing current through each connection.

 

[Short_Shot]

I understand that you were talking about the cables, but perhaps the reason they spec 2 smaller cables instead of one larger cable is because of the fact that now there is 2 lugs making contact, increasing the surface area for that connection, reducing current through each connection.

Are there two posts? Otherwise they're just stacked and it isn't really increasing the surface area at all.

 

[corn18]

Are there two posts? Otherwise they're just stacked and it isn't really increasing the surface area at all.

There are 2 posts.

 

[Short_Shot]

Then that sorts it. A better option all around.

 

[noenegdod]

Are there two posts? Otherwise they're just stacked and it isn't really increasing the surface area at all.

Haha, There is the disconnect! Yup, there are two posts.

 

[corn18]

This is what Victron recommends:

 

[curiouscarbon]

(NB: different model multiplus terminals)
24/3000

 

[DaPhatty]

Slightly off topic - What did you use to create your electrical layout drawing? I've been looking for a tool that would help me with this process without having to jump into Photoshop.

 

[corn18]

Slightly off topic - What did you use to create your electrical layout drawing? I've been looking for a tool that would help me with this process without having to jump into Photoshop.

I used PowerPoint. I got my PowerPoint ranger badge while at megacorp.

 

[DIDDLYV]

I plan to just double up the 2/0 cable I have now. I have 2/0 running to both inverters that are currently installed so I will just reuse that. Looking at the pdf of the connections, I’m not sure if 4/0 would fit the lugs or not. If it would fit, I would prefer a single cable vs 2.

They have 2 binding terminals for the postives and negatives

 

[corn18]

Ordered the VME 12/3000/120x2 today. Also got the MK-3 USB adapter and a multi control panel. Not ready to drop the $500 for a Cerbo and GX panel. I'll do that if/when I switch to Victron SCCs.

 

[corn18]

Went nuts and decided to go all Victron. Anything I am missing?