Dual Victron Multiplus Inverters vs Multiplus 2x120 for 50 amp RV

[Dragoth]

I am building a system for my 50-amp RV. I have decided on Victron components, but am struggling to decide exactly which inverter setup to go with. I want to eventually be able to run EVERYTHING in my RV off solar even if I can't do it right away. My current hang-up is that I want the power output of (2) 3000-VA inverters, I will occasionally hook into shore power, and have an onboard 5kw generator that will supplement as needed. Can you set dual inverters to handle the 50 amp or am I better off getting the 2x120? If I should have the 2x120 do you need 2 of them or can you do (1) 2x120 and 1 standard inverter? I've spent hours researching this and feel I'm no closer to finding the answer so I came here hoping for some clarity. TIA

 

[Adam De Lay]

Do you need split phase (240v) or is everything 120v?

 

[Dragoth]

Do you need split phase (240v) or is everything 120v?

I am not aware of a need for 240v. As far as I know, everything is 120v and although I have thought about adding a mini-split, I'm sure I could find a 120v version unless there is a large advantage to using a 240v one.

 

[jberger]

Do you know how your current RV is wired for shore power?
What inverters do you have today?

You mention a 5000w generator but wanting to run (2) 3000 watt inverters, so I'm guessing you have a converter in your current system that is limiting you to only using certain outlets and you want to replace all of that with the new inverter system.

You need to figure out exactly what you want to run on battery power and for how long, then start sizing the equipment.

Given that you only have a 5000 w generator today, I'll assume you don't actually need 240v in your system, but then you mention wanting to add a mini split.
If you really want to run 6000w from batteries, it's going to need to be a big battery bank and inverter setup.
Spend time on the actual use case, then worry about the equipment list, otherwise you are going to just be throwing money at an undefined problem hoping to achieve an undefined outcome.

 

[Dragoth]

My RV currently has a small 2000w inverter. I'm switching from 12v to 24v and have (2)-24v 200AH server rack batteries. I need to have enough power to run a residential fridge 24/7 and would like to have enough power to run at least one A/C for a few hours a day, along with all the normal things that need to be powered (lights, tv, etc.) I am not opposed to replacing the rooftop A/C units, but I'm torn on a traditional mini split because my rig is a toy hauler and I don't have anywhere to install the outside unit without significant modifications.

I started with 2 batteries because that was what I could afford at the time, but I have always planned to add at least 1 maybe 2 more depending on power needs. Same with solar panels, I currently have 1200 watts, but that is only because that is what I could afford at the time and I have plans to add more. My philosophy is that I would rather build a system now that is easily expanded upon but is overkill for what I will need as I always want to have more power than my needs than not enough even if that means spending more than I need to. I wholeheartedly believe that it's better to overdesign a system.

I'm going full-time in this rig very soon so I need reliable power and I don't want to be constantly watching my battery bank worrying about whether I'm going to run out.

I will head out to the RV and do some tests on some of the items I'm going to be powering since I haven't done that yet. Get an idea of power consumption and go from there. When using a kill-a-watt style meter, how long is good enough for an accurate reading of power consumption? Should I let it go for 24 hours or is an hour or two good enough for accuracy? I'm going to assume something like the fridge with power that fluctuates due to compressor would need longer than a TV?

 

[jberger]

You would be better off going 48V for the new system, and skipping 24V. There is not much point in 24V if you are starting over.

Is the fridge a residential fridge or the typical 3way rv fridge? I couldn't tell if you already had replaced it or were planning to. My residential fridge uses less power than the old 3 way model if that helps.

I would test the power usage of all the stuff you can easily plug into the killawatt. An hour each should get you the info you need on everything but the fridge and AC.
Stuff like WiFi and Starlink can use a lot more than you think when you calculate for 24 hours.
You will want to look at the AC needs closely, because other than the fridge, it will be your biggest load over 24 hours.
Water heating is the other thing that will really cost you unless you can run propane/diesel.

Get as much Solar on the roof as you can, and see how many batteries you can reasonably install, that will be the limiting factor on run time. The only reason you would need a 240v output would be for a mini split, and EG4 has those solar mini split options. I would skip 240v and keep your inverter setup simple.

 

[Dragoth]

You would be better off going 48V for the new system, and skipping 24V. There is not much point in 24V if you are starting over.

Is the fridge a residential fridge or the typical 3way rv fridge? I couldn't tell if you already had replaced it or were planning to. My residential fridge uses less power than the old 3 way model if that helps.

I would test the power usage of all the stuff you can easily plug into the killawatt. An hour each should get you the info you need on everything but the fridge and AC.
Stuff like WiFi and Starlink can use a lot more than you think when you calculate for 24 hours.
You will want to look at the AC needs closely, because other than the fridge, it will be your biggest load over 24 hours.
Water heating is the other thing that will really cost you unless you can run propane/diesel.

Get as much Solar on the roof as you can, and see how many batteries you can reasonably install, that will be the limiting factor on run time. The only reason you would need a 240v output would be for a mini split, and EG4 has those solar mini split options. I would skip 240v and keep your inverter setup simple.

Hindsight is 20/20. Unfortunately, I already purchased two 24v batteries so I'm going to stick with 24v and sleep in the bed I've made myself already. If that means bigger wires, then so be it, but my wire runs should be short so I'm not too concerned.

 

[DIYrich]

Hindsight is 20/20. Unfortunately, I already purchased two 24v batteries so I'm going to stick with 24v and sleep in the bed I've made myself already. If that means bigger wires, then so be it, but my wire runs should be short so I'm not too concerned.

See if you can put the two 24v batteries in series to make 48v.

 

[littleharbor2]

Air conditioning is a huge load, much more than refrigeration. I figured I could easily run my 12,000 btu. mini split off my 2100 watt array. What I didn't figure was the fact that I still have all my other loads running and battery charging to contend with.

Normally I get up in the morning to 70 - 72 % battery bank. After running my ac. about 4 hours in the afternoon I was waking up to 40% soc batteries. Pretty easy to tell I wouldn't be able to maintain this scenario for long. My solution, which isn't practical in your case was to add a separate dedicated 2200 watt array and inverter, for the ac. BTW, there are many 12,000 btu 120 vac Mini Split units to choose from.

 

[Dragoth]

See if you can put the two 24v batteries in series to make 48v.

I contacted Signature Solar support to ask this question and this was their response:

"Yes, you can however it's not recommended and you will notice issues with your system long term if you do this. Battery banks are best run in Parallel with one another at 48vs each. Putting Batteries in series removes any ability to put them in closed loop communication and will cause greater drifting between batteries charging because the inverter thinks two 24v batteries are the same battery but they are not functioning like a single battery it's going to have issues with properly reading voltage while those batteries struggle to distribute power equally."

 

[DIYrich]

I contacted Signature Solar support to ask this question and this was their response:

"Yes, you can however it's not recommended and you will notice issues with your system long term if you do this. Battery banks are best run in Parallel with one another at 48vs each. Putting Batteries in series removes any ability to put them in closed loop communication and will cause greater drifting between batteries charging because the inverter thinks two 24v batteries are the same battery but they are not functioning like a single battery it's going to have issues with properly reading voltage while those batteries struggle to distribute power equally."

Problems with keeping 24v batteries balanced, or 24v issues.... I choose 48v.

 

[Dragoth]

Air conditioning is a huge load, much more than refrigeration. I figured I could easily run my 12,000 btu. mini split off my 2100 watt array. What I didn't figure was the fact that I still have all my other loads running and battery charging to contend with.

Normally I get up in the morning to 70 - 72 % battery bank. After running my ac. about 4 hours in the afternoon I was waking up to 40% soc batteries. Pretty easy to tell I wouldn't be able to maintain this scenario for long. My solution, which isn't practical in your case was to add a separate dedicated 2200 watt array and inverter, for the ac. BTW, there are many 12,000 btu 120 vac Mini Split units to choose from.

Just curious, what voltage is your DC system and how big is your battery bank?

 

[Dragoth]

Problems with keeping 24v batteries balanced, or 24v issues.... I choose 48v.

Sorry for my ignorance, what issues do 24v systems have over 48v besides wire size/ amperage?

 

[littleharbor2]

Just curious, what voltage is your DC system and how big is your battery bank?

My main system is 24 volt. My battery bank is 11.5 kwh LiFePo4 prismatic cells DIYbank.