Quattro 48/15000 or Multiplus II 48/15000 -- which is better (for our application)?

[AlaskanNoob]

We are almost ready to install our completely off grid, and to remain off grid, solar system. We own and will implement everything in the system as is, according to the design below, with the exception of the Multiplus II 48/15000 shown in the top left of our diagram (we planned to order it but have not yet). But now, we are considering a Quattro 48/15000 instead of the Multiplus II 48/15000. Any thoughts one way or another on which would be better for our application as we've tried to diagram it out below or any experience with these devices you could share?





The differences I detect, are:

• The Quattro will allow bringing in two sources of AC power to the MP's one. This would allow us to hook up a second generator which is a plus. I gather only one generator at a time can run though, but perhaps with relay programming it could be such that it tries to autostart one and if it doesn't run (because it's out of fuel) it tries to start the other?
  
  
• The Quattro's peak power is 2KW less and its zero load draw is about twice as much as the MP.
  
  
• If I'm reading the data sheets correctly, the Quattro has 3 programmable relays while the MP has one?
  
  
• The Quattro is slightly lighter.
  
  
• The BIG plus I see is that *apparently* the Quattro can actually be operated in parallel (or so it says on the data sheet under "System Configuring").
  
  I would need it to charge my Pylontech batteries, and the Victron Compatibility guide says the Quattro will work with them. And, most importantly, I would need it to send single phase 240V to our cabin 700 feet away to the Autotransformer and the Autotransformer manual says it works with Quattro.
  
  I'm curious if there is any difference between the two as far as handling dump loads when the batteries are full and the PV is still bringing in power and has more power than current AC loads?
  
  Is there any fatal flaw I'm missing with the Quattro in our application instead of going with a Multiplus II 48/15000? Many thanks for any help or experiences shared about this equipment.

 

[sunshine_eggo]

• The Quattro will allow bringing in two sources of AC power to the MP's one. This would allow us to hook up a second generator which is a plus. I gather only one generator at a time can run though, but perhaps with relay programming it could be such that it tries to autostart one and if it doesn't run (because it's out of fuel) it tries to start the other?

Correct. Only one active source at a time. Generator auto-start is a single event feature, i.e., if the generator doesn't start, there is no fall back to a second generator; however, there are means of starting up a second generator through other devices, but I don't know how that will interact with the BMS. The inverters themselves can have on-board programming for gen auto-start, so you could define a second criteria below the first. I just don't know if an inverter under BMS control would still execute those rules.

• The Quattro's peak power is 2KW less and its zero load draw is about twice as much as the MP.

Surprised to see the -2k, but yeah. The "II" versions focus heavily on reduced idle power consumption, so the MP-II is notably lower.

• If I'm reading the data sheets correctly, the Quattro has 3 programmable relays while the MP has one?

I see the same, but I don't know for sure.

• The Quattro is slightly lighter.

That's really surprising, but that's what the datasheet says!

• The BIG plus I see is that *apparently* the Quattro can actually be operated in parallel (or so it says on the data sheet under "System Configuring").

Given the MP issue, I wouldn't trust this without 100% verification by Victron proper.

• I would need it to charge my Pylontech batteries, and the Victron Compatibility guide says the Quattro will work with them. And, most importantly, I would need it to send single phase 240V to our cabin 700 feet away to the Autotransformer and the Autotransformer manual says it works with Quattro.

Shouldn't be any different than a MP-II in this regard.

• I'm curious if there is any difference between the two as far as handling dump loads when the batteries are full and the PV is still bringing in power and has more power than current AC loads?

No. There's no such thing as a dump load when it comes to PV. MPPTs are LOADS to the PV array(s). When demand decreases and battery voltage rises in response to the incoming power, the MPPT reduce their load on the array.

• Is there any fatal flaw I'm missing with the Quattro in our application instead of going with a Multiplus II 48/15000? Many thanks for any help or experiences shared about this equipment.

Unless it gets you what you want with parallel expansion, I don't see a compelling reason. Additionally, as I recall, the AT is already a big limiting factor.

The only reason I got Quattros over MP is because they didn't have 48/5000 MP at the time.

 

[AlaskanNoob]

No. There's no such thing as a dump load when it comes to PV. MPPTs are LOADS to the PV array(s). When demand decreases and battery voltage rises in response to the incoming power, the MPPT reduce their load on the array.

So in order to use the extra PV power, I would need something to know that the batteries are full, and to add AC loads or DC loads through a relay that turns those loads on?

The ability to expand is what we had planned for, because we're planning on having one system run various things on the property. So it's not just the cabin we'd expand for. So the ability to parallel is a big one for us and has us thinking we'll go the Quattro route.

Our 700 foot cable to the cabin can handle 6 x 15K Quattros in parallel although I cannot fathom ever needing that much power. I just saw a YouTube channel that has 2 x Quattro 10Ks in parallel so I'm confident the manual is correct about the 15K being able to be paralleled. And I would be comfortable paralleling these since they use M6 lugs for the AC connections and not those plastic housings.

If we wanted to expand power to the cabin, we could have 2 x Quattro 15K in parallel and that would send 100A to to the Autotransformer there.

As far as I understand it (which is not at all), we can have multiple Autotransformers on other wires to other structures on the property besides the cabin. Then we could a) design the system to be floating such that the relay to the ATs aren't needed since we're off grid, b) wire a single relay to a single AT and it would ground as required for the whole circuit, or c) have multiple relays to each autotransformer on the property and they would all ground at the same time which is not something we would likely want to do as multiple grounds are not good, but that option would exist too. We will definitely hire a pro to design the grounding and figure that out and an electrician to implement it.

The Regional Manager offered up the Quattro as a solution and I think it's a very good one. He's going to send us a new Quattro 48/15000 at no cost, he will pay the shipping, and we will pay to ship one of our Multiplus II 48/8000s back to the dealer. That's a good solid resolution to the issue. We'll keep the other 48/8000 for another project where we set up a smaller solar array on a different property to charge a RAV4 Prime.

Despite the frustration and stress, Victron has put us in a better spot than we were when we started.

 

[sunshine_eggo]

So in order to use the extra PV power, I would need something to know that the batteries are full, and to add AC loads or DC loads through a relay that turns those loads on?

Yes.

This is where something like a BMV shunt with it's control relay can signal on/off at a voltage, SoC and temperature to control the "dump load". There are likely other options with the inverter programmable relays and software assistants, but I'm not familiar enough to say for certain.

 

[Rocketman]

I believe the Cerbo can open and close a relay so you can start and stop dump loads. I believe it has it all available.
The how would be another good question for the Victron dealer

 

[sunshine_eggo]

I believe the Cerbo can open and close a relay so you can start and stop dump loads. I believe it has it all available.
The how would be another good question for the Victron dealer

Yep. I didn't see that the Cerbo has a second relay. My CCGX only has one, and it's more limited than the Cerbo.