Maximizing Solar and Inverter Setup for High-Power RV Needs

[Primerump]

I’ve considered redundancy, but isn’t that essentially the only real advantage?

Correct me if I’m wrong, but with two 48-volt batteries I would have approximately 9,600 watt-hours while only adding about 150 pounds and taking up very little space. To achieve the same watt-hours at 24 volts, everything would effectively double—size, weight, and battery count—unless I were to spend significantly more on a couple of 230 Ah batteries.

the power density of 48@100Ah or 24@200Ah is the same. the batteries will consume the same physical volume. what is different of course is the layout and packaging. the reason for my suggestion is just simplicity, it's the least complicated setup and satisfies your requirement, and works off 240 or 120V or a generator.

My rv has a single multiplus 2 fed from 24V, configured as a UPS. I have 19,200 Wh capacity in the form of four 12V 400Ah batteries in a 2S2P configuration. they take up very little extra space vs a 48V equivalent pack.
In fact, because they are thinner and longer than a 48V pack, I am able to fit them in a space that I could not utilize with a rack style 48V unit.!

yes, you are correct, 2x48V 100Ah batteries are indeed 9600Wh. a 24V 400Ah pack would be the same.
best option is to size batteries to fit available space rather than just saying "i'm going to use xxx or yyy" just because..

if you intend to run two inverter units I would suggest a minimum of 24V 400Ah.
commodity grade of that capacity is around $1200. not expensive at all.
if you ran just one unit, you could upgrade later by fittng a second unit in parallel ( having first configured them for parallel operation ).

 

[Wmlunt-WO]

WOW thanks for all the info. I have made a few adjustments, well just one! I am moving to one 48V 100AH LiFePo4 and I have room for one more if needed. I also have the 50 amp ATS on the way as well. I am looking at the victron 48V 5000 240V MultiPlus-II. This is a 50-amp RV with inverter prep, but the inverter prep wiring is only 10-gauge. I have one inverter-prep breaker on each leg of the main breaker panel.
My understanding is that the Victron 240-volt, 5kW MultiPlus-II provides split-phase output to the panel, feeding each leg of the breaker panel. I also assume the total output is 5kW, split between the two legs rather than 5kW per leg.

Is this split-phase output the primary difference between the 240-volt and 120-volt MultiPlus-II models?

Since I do not currently have any 240-volt loads in the RV, I am trying to understand whether there is a real advantage to using the 240-volt unit versus the 120-volt version. Are there any additional benefits or drawbacks I should consider when choosing between the two?

I also have some confusion regarding the transfer switch, since my generator is only 120 volts.

On the generator side of the automatic transfer switch, do I bond L1 and L2 together, since the generator only provides a single hot conductor, neutral, and ground? In contrast, the shore power feed has two hot conductors, a neutral, and a ground, and the wiring going from the transfer switch to the inverter and main breaker panel is also two hots, a neutral, and a ground.

. . and yes I am working on solar pannels on a slide, so I can slide out over the bump outs, and I did find 450 watt pannels so that should help.

Thank you for your guidance—I appreciate any clarification you can provide.

Never bond L1 and L2 together!!! Bad idea!

 

[Primerump]

Never bond L1 and L2 together!!! Bad idea!

A 50A to 30A dogbone does just that. it connects both L1 and L2 of the RV side to the L1 of the 30A supply. standard practice, no issues. if you connect L1 and L2 on a 50A ( 240V supply ) then yes, you are in for a surprise...

 

[Primerump]

"On the generator side of the automatic transfer switch, do I bond L1 and L2 together, since the generator only provides a single hot conductor, neutral, and ground? In contrast, the shore power feed has two hot conductors, a neutral, and a ground, and the wiring going from the transfer switch to the inverter and main breaker panel is also two hots, a neutral, and a ground."


for dual voltage use such as 240 shore power and 30A single phase generator you would connect the ATS like this:

240V 50A = Hot L1 ( typically RED ) to L1 input on SHORE side of the ATS
Hot L2 ( typically black ) to L2 input on SHORE side of the ATS.
Neutral ( typically white ) to the N input on the SHORE side of the ATS

on the 120V 30A generator side.
Hot L1 from genny to L1 + L2 ( a bridge ) on the INPUT side of the ATS
DO NOT SHORT the output side. - very important...

Connect the Neutral to the N input.

when on shore 50A the ATS will pass through two hots and a neutral.
When shore is disconnected and generator is started
the ATS will switch the Single hot of the genny to both L1 and L2
it will function as if it was connected to a 30 to 50A dogbone adapter.
if you connect a 30 to 50A dogbone adapter to the 50A shore input, the ATS will
sense this and function normally.

 

[Wmlunt-WO]

A 50A to 30A dogbone does just that. it connects both L1 and L2 of the RV side to the L1 of the 30A supply. standard practice, no issues. if you connect L1 and L2 on a 50A ( 240V supply ) then yes, you are in for a surprise...

I would never tell the average Joe to connect L1 and L2 together. Adapter cords use plugs to attempt cross wiring protection. The use of a 50/30 adapter is a much safer prospect than instructing them to connect 2 hot wires on a system, RV, home, work, etc.
In this litigious society they now know who to sue for damages…

 

[Primerump]

I would never tell the average Joe to connect L1 and L2 together. Adapter cords use plugs to attempt cross wiring protection. The use of a 50/30 adapter is a much safer prospect than instructing them to connect 2 hot wires on a system, RV, home, work, etc.
In this litigious society they now know who to sue for damages…

I'm quite sure you do not understand what the application is else you would know exactly what's happening here.

L1 and L2 are joined at the ATS for single phase 30A supply JUST AS IF IT WAS A 30 to 50A DOGBONE ADAPTER. there is no difference. it is standard practice.

you can by one of those adapters and disect it if you so desire, all you will find is the L1 bonded to the L2.

the ATS is a double pole relay that by design isolates the two inputs, so it's not possible under normal operating conditions to short one input to another as you seem to imply.

what you are mistaking here, or assuming is bonding the 50A pedestal L1 and L2 together.. that is not what is happening here and if you did you would trip the pedestal breaker instantly.

just to be quite explicit clear here, I am not suggesting or instruction anyone to connect a 50A L1 and L2 supply together that would be very stupid. the instructions here are to connect the L1 and L2 of the ATS input together on the generator side when supplying power from a 120V generator. that is all.

and yes, i know about today's litigious stupid society. as a former and now retired professional engineer i have had to carry $10M in insurance coverage for certain contracts in the past.

i wonder if all those diy youtubers have coverage too ?

 

[Wmlunt-WO]

As a retired engineer with 45 years machine design experience I know exactly what you are discussing. Sadly not every average joe knows one voltage from the next, and I stand by my statement that it makes no sense to tell people to short wires together. Those that know electrical circuits know what to do, those that don’t shouldn’t just tag 2 hot wires together cuz they read it on the internet.
This is a dangerous suggestion!

 

[FiveOclcok]

Thank again for the help, I think I have found the answer for the inverter. I really like the Quattro 48/5000/70/100/100 and would be sold on it if it were available in the Quattro II version. I did find an MP2 48/5000/70/100-120, although it is currently on backorder, and I believe this may be the better option for my application.

While I like the dual-input capability of the Quattro, I am not a fan of the 35-watt idle consumption. The MP2, by comparison, only draws about 15 watts at idle. I realize I may be putting too much emphasis on what is ultimately a small difference, but the lower idle draw is appealing. Additionally, the MP2 is less expensive overall.

Although the MP2 would require adding an external ATS upstream, those are relatively inexpensive these days—only a few hundred dollars—so that does not significantly affect the decision. Am I putting to much emphasis on the idle wattage? The dual inputs would be nice!

 

[Primerump]

Thank again for the help, I think I have found the answer for the inverter. I really like the Quattro 48/5000/70/100/100 and would be sold on it if it were available in the Quattro II version. I did find an MP2 48/5000/70/100-120, although it is currently on backorder, and I believe this may be the better option for my application.

While I like the dual-input capability of the Quattro, I am not a fan of the 35-watt idle consumption. The MP2, by comparison, only draws about 15 watts at idle. I realize I may be putting too much emphasis on what is ultimately a small difference, but the lower idle draw is appealing. Additionally, the MP2 is less expensive overall.

Although the MP2 would require adding an external ATS upstream, those are relatively inexpensive these days—only a few hundred dollars—so that does not significantly affect the decision. Am I putting to much emphasis on the idle wattage? The dual inputs would be nice!

if you are determined to use 48V then the Quattro will do the job, if fact for 5000VA you will be much better off using 48V. the Quattro is basically the big brother of the multiplus.

for the ATS, you will feed L1,L2 and N into the shore side. L1 and N on the generator side.
here are the power flows for both split and single phase inputs

 

[Primerump]

just looking at this again and I would favor the dual MP2 2x120 units. just based on all round simplicity .

 

[FiveOclcok]

Ok so I have thought about this long enough,(not really).
Thanks for the good information. After researching the transformer option further, I’ve decided that installing two inverters makes the most sense for my setup. Going that route allows me to step down to two 3000-watt units, and I just can’t justify spending roughly $500 on a transformer when that money could instead go toward another inverter.

At this point, I’m comparing the MultiPlus II 3000 versus the Quattro 3000. Below are the differences that I think may matter, and I’d appreciate feedback from anyone who has already gone down this road.

• Peak power:
  The MultiPlus II is rated at 5,500 W peak, while the Quattro is 6,000 W peak. I don’t expect either unit to ever run at peak output, and even if it did, I’m not sure the extra 500 W would make a real-world difference.
• Zero-load consumption:
  The MultiPlus II draws about 13 W, compared to 25 W for the Quattro. This isn’t a deal breaker, but since the system will likely be sitting at little to no load when we’re not in the rig, lower idle consumption is a plus.
• Starting battery charging:
  It appears the Quattro may be able to charge the starting battery. Am I reading that correctly? If so, that would be a definite advantage if it can also support the 12-volt system.
• Automatic transfer switch (ATS):
  The Quattro includes a built-in ATS. That’s convenient, but not a major factor for me since external ATS units are relatively inexpensive, especially considering the cost savings of the MultiPlus II.
• Size and weight:
  Both units weigh about the same. The MultiPlus II is slightly larger, but space is not an issue in my installation.

The biggest factor for me is cost. Two MultiPlus II 3000 units come out to $2,337.50, while two Quattro 3000 units total $3,052.00. That’s a savings of about $715, which is hard to ignore.

Given all of that, I’d really value input from anyone who has practical experience with either setup and can comment on what differences truly matter in real-world use.