Suggestions for 45' Motorhome conversion to 48V or stay 12V?

[Lt.Dan]

Also expect there are some people who are entirely electric dependent for their energy. I drive an EV, and all my appliances are electric.

It doesn't help that I mine crypto as well, but thats besides the point..

 

[Checkthisout]

I'm shocked! With my 12V coffee maker, diesel heater and desktop, I barely break 0.4kwh a night... but I guess a home does have more power-hungry appliances.

Consider converting diesel consumption to kilowatts and making that your total.

Houses etc that use: Gas/propane etc for hot water, clothes drying, heat and cooking will have myriad less electrical consumption than an all-electric house.

 

[Rocketman]

I would go 48v - for your list of equipment I would go with two Multiplus II 48/5000 in split phase.

I fulltime in a MotorHome with a Multiplus 12/3000. Too many times my wife will be running the microwave and then turn on another high amp device: toaster, kitchen aid mixer, hair dryer, instant pot, etc. and the inverter shuts down due to overload.

Unless your two phases are done so you can’t overload one with too much load, look at increasing the inverter size a bit.
It will only cost a few dollars, some extra space(?), and extra standby watts.

Good Luck

 

[chrisski]

Boondocking in perfect weather no heat or air conditioner, I’m at 1.2 kWh per day.

When it’s hot in AZ and With two ACs running at 1.7 kWh each and it’s so hot they never shut off, electric hot water at 1.4 kW, and the the 300 watt fridge on 80% of the time, that’s at least 60 kWh. Not sure the exact number since I’d be hooked up at a park.

 

[justinm001]

What genset do you have? 48v makes a ton more sense over 150a

Couple things, the Mp2 2x120 does not provide split phase power, it'll just pass through 240v when connected to shore and when inverting it's just 120v. This means you cant use your cooktop when on inverter.

Running a pair of Victron 3k inverters in split phase setup will give you 240v on inverter and shore, even allow you to use 15a 120v shore but still provide 240v (turn off switch as group).

3k Inverters on split phase setup only give 3k on each leg so if you're using over 3k on 1 it'll overload the inverter. You don't get 6k, like you would if stacked 120v parallel.

The MP only supports 50a total output on each leg. This means hooked up to 50a shore you only get the 12kw total. So washer/dryer, and cooktop and AC isn't going to work at same time.

I went with dual Quattro 5ks because they have dual inputs so aut transfer from genset to shore but they also support 100a on each input and output. This means I can pull 50a 240v (12kw). But power assist an additional 10k so 22kw total, or 11kw on each leg. Meaning I don't need to worry about balancing either leg as I can pull like 90a on one leg while that inverters assisting the other is charging the batteries.

 

[justinm001]

Average home is in the 30-50kWh a day.

My home? 80-120kWh a day.

I have 3 houses (airbnb 2 of them) and they're 66-100kWh/day. This spring's goal is to use home automation and lower these.

 

[steined]

Thanks for all the insights. I think we're going to stick with 12V if I can make it work. If I had the time I'd play with the 48v to 12v system, but it does seem like a lot of added complexity.

For the 12/3000/120 Multi Plus II in split phase, can you use an auto transformer to balance the output, or does it not work like that due to the split phase nature? Autotransformers are outside my range of understanding.

I can pretty easily replace the 3500W max 240V cooktop with an 1800W 120V unit to remove the 240V requirement, and get a 12k 120V Mini Split instead of the 18k. So I can be talked out of the split phase.

As for what I want to run all the time, this is for boondocking in a "chase the 70s" situation with occasional days of "I need some AC", not Florida Everglades in June type environments. It's also for when we're on 30A (or mooch docking on 15A) and we want to run all the AC because we're not in ideal weather but not bother people with the generator.

Calculating peak usage loads, about 5,100 W
Minisplit 1200 Watts worst case
Microwave/convection oven (1500w)
Cooktop usage (up to 1800W) OR an instant pot (800 watts).
Residential fridge doesn't use a ton of power, usually in the 400W range when running.
Residual Class A BS Loads ~200 Watts

It seems like leg imbalance could be an issue, but I could probably mitigate that in the panel to some extent. I would prefer to avoid the auto transformer if possible.

Does this sound reasonable? Most of the time it will be the 200W residual loads + 400W Fridge intermittently and then some loads of laundry and cooking periodically. I have a 12V fridge that uses around 1.5kWh a day, and the base load of lights is .4kWh a day

Someone asked what generator I have, it is an Onan 10000 Diesel with split phase output (240V). I have never run out of power while running the generator, but I know I could do it if I tried. No need though.

 

[justinm001]

Thanks for all the insights. I think we're going to stick with 12V if I can make it work. If I had the time I'd play with the 48v to 12v system, but it does seem like a lot of added complexity.

For the 12/3000/120 Multi Plus II in split phase, can you use an auto transformer to balance the output, or does it not work like that due to the split phase nature? Autotransformers are outside my range of understanding.

I can pretty easily replace the 3500W max 240V cooktop with an 1800W 120V unit to remove the 240V requirement, and get a 12k 120V Mini Split instead of the 18k. So I can be talked out of the split phase.

As for what I want to run all the time, this is for boondocking in a "chase the 70s" situation with occasional days of "I need some AC", not Florida Everglades in June type environments. It's also for when we're on 30A (or mooch docking on 15A) and we want to run all the AC because we're not in ideal weather but not bother people with the generator.

Calculating peak usage loads, about 5,100 W
Minisplit 1200 Watts worst case
Microwave/convection oven (1500w)
Cooktop usage (up to 1800W) OR an instant pot (800 watts).
Residential fridge doesn't use a ton of power, usually in the 400W range when running.
Residual Class A BS Loads ~200 Watts

It seems like leg imbalance could be an issue, but I could probably mitigate that in the panel to some extent. I would prefer to avoid the auto transformer if possible.

Does this sound reasonable? Most of the time it will be the 200W residual loads + 400W Fridge intermittently and then some loads of laundry and cooking periodically. I have a 12V fridge that uses around 1.5kWh a day, and the base load of lights is .4kWh a day

Someone asked what generator I have, it is an Onan 10000 Diesel with split phase output (240V). I have never run out of power while running the generator, but I know I could do it if I tried. No need though.

There's a huge difference between a 1800w cooktop and a 3500w. 1800w you're only getting 1 burner on high and if 2 they're barely getting to medium. I'm bout to replace mine with 240v because it's a pain to cook with.

I doubt a single 12k mini split will cool your coach.

They dont make a MP split phase but they make a MP2 2x120 which has split phase coming in and will allow split phase out when connected, but invert on both lines 120v when on 120v or just inverter.

I'd really suggest getting 2 separate MP 3000w inverters and program them as split phase. This way you can have 120 or 240v coming in and 240v out and have 3000w on each leg when inverting. Can run all your loads and easily get a 18k mini split.

48v isn't more complexity you just get 48v battery's, 48v inverter and a 48/12 DC DC converter for your 12v loads as well as a 12/48 converter for your alternator. If going 12v you still need a 12/12 DC converter for the alternator so the only difference is the 48/12 converter to power your 12v loads like lights. Which BTW is better because all your 12v loads get a solid voltage so no flickering or anything.

But for only 3000w it's fine either way and same cost as the wire savings for 48v is offset by the converter cost. It's just easier to manage since smaller wires everywhere. It's 5000w where you really want 48v.

 

[Rocketman]

One question is where in the rig you will put everything… make sure you have this all mapped out.

In my MotorHome I have Victron equipment in four different areas - all spread out. I reused the OEM wiring which because of very long lengths has created some voltage drop issues.

Good Luck

 

[Checkthisout]

I reused the OEM wiring which because of very long lengths has created some voltage drop issues.

A good reason to go with 48 Volt over chassis voltage.

 

[steined]

I'd really suggest getting 2 separate MP 3000w inverters and program them as split phase. This way you can have 120 or 240v coming in and 240v out and have 3000w on each leg when inverting. Can run all your loads and easily get a 18k mini split.

Justin, thanks, would you suggest 2 x MP 2 12/3000/120 2X120's or 2 of the "regular" MP 2 12/3000/120's?

I'm leaning towards this and potentially even an autotransformer on the output so I can use more than 3000 watts on either leg if needed. In this configuration would it be using the autotransformer on paralleled MP 2's and getting the split phase out of it as well?

 

[justinm001]

Justin, thanks, would you suggest 2 x MP 2 12/3000/120 2X120's or 2 of the "regular" MP 2 12/3000/120's?

I'm leaning towards this and potentially even an autotransformer on the output so I can use more than 3000 watts on either leg if needed. In this configuration would it be using the autotransformer on paralleled MP 2's and getting the split phase out of it as well?

The 2x120 is an odd device so idk if they work in split phase. It would be best to get 2 of the regular MP or MP2 and setup in split phase so you get 240v and 3000w on each leg. You could also setup as parallel where they're stacked and you only get 120v but 6000w, although the 2x120's would be better as you'd get 240v input.

I'm not too sure the differences between the Multiplus and Multiplus2 other than different sizes. The Quattro has dual inputs so works as an auto transfer switch for my genset and it handles 100a on every in/out which I have a 20kw 240v genset so needed the extra power. Works nice and logs how much I use each source. In 2024 I've only used 4.8kWh on genset and plan on never really using it at all.

If you properly balance the devices on the legs it doesn't really matter. Put the AC above the kitchen on one then the back AC with the cooktop. This way you can run both ACs or 1 AC and the cooktop, plus plenty of room for smaller random loads. Same with microwave and cooktop being on separate legs.

Whats nice with Victron is when you get the CerboGX you can see both legs and both inverters. Here's mine and I just turned it from inverter to shore and its maxing out my 27A/240v limit using 2968w on one in leg and 2660w on other coming in but 306w/490w output. I have Quattro 5000w inverters so rarely get to my 5kw limit on each leg unless I'm trying ( I have 6 ACs).


I don't see the point in an autotransformer. I believe they're only 32A continuous. The only time I've seen these uses is for a specific appliance like a washer/dryer where that circuit they'll convert the 120V to 240V. Although I have a 120v combo washer/dryer and it seems to work, I saw new 120v heatpump ones at hd/lowes and they seem even more efficient. Running a 240v electric dryer off an inverter is just a bad idea, it'll drain batteries like crazy. the 120v ones need to be efficient and even though they take 4 hours they spin the clothes and drain with a bit of heat instead of 10kw of heat for an hour