5th wheel power system. Decisions to make. inverter, charge controller, DC converter, etc

[fastline]

We use a 5th wheel as an office at a plant nursery but also like to use for a couple trips. I say this because we run it off of solar primarily, but not really enough power. There is no grid power.

Right now a 5th is setup with only a 1000W 12V inverter and separate charge controller with a max of 580W at 12V, but I can crank that up if we raise the battery voltage.

The issue with RV/5th is their DC systems are 12V so if I change battery voltage, I will need a DC:DC converter. Most of the DC does not need too much power though. But to complicate this, we are going to use a different 5th that has a dedicated inverter for the refrigerator that runs off of 12V. I have half a mind to delete this and run it only on AC.

What I have before me are these options.

1. Remain on 12V and buy gear only for that, realizing the limits and larger wire.
2. Buy a real solar inverter/charger, that would have an ATS, charger, and charge controller built in. And combine this with a 12:48V converter
3. Buy or use existing charge controller with 48V bank. Then buy a 48V inverter for AC power.

I am also quite open to 24V as well but I think once we walk this line, might as well move to 48V?

Obviously this is more of a "financially efficient" decision more than anything.

As far as inverter/chargers, I have been drawn to MPP gear, though no direct experience yet. I think their stuff is built decent and NOT China! I am open to other ideas here. Just trying to solve the issue. Usually the rig will be on solar panels but when leaving the property, probably run on a genny for charging mostly.

I had great interest in a "hybrid inverter" that can use both generator and solar power, but just not willing to spend the coin with the big dogs for that yet unless a cheaper unit can do it? that would obviously be most ideal!!!

 

[FilterGuy]

What size inverter do you want to put in. 12V is OK up to ~2500W. Many people do 3000W on 12V, but IMHO, that is pushing them limits.

I am also quite open to 24V as well but I think once we walk this line, might as well move to 48V?

There are more components available for 24V than 48V. In particular, be sure to look at the available buck converters (and boost converters) before you make a decision.

 

[fastline]

Probably targeting 3000W right now.

What I am most interested in beyond the voltage is an inverter that is capable of running solar combined with the generator. Usually it is one or the other, which is just not acceptable for my application.

Basically I want to run at least one of the air conditioners from solar, in which there will be days with overcast and not enough solar so I want to just use a small generator as the supplement.

Basically beyond all this, I have to think about redundancies and backup plans. If I convert everything for a 48V solar inverter, I have to think about plan B if/when that fails.

 

[HRTKD]

I use separate devices. Solar charge controller and then an inverter/charger. If I'm on shore power or the generator I can still get a charge from the solar charge controller. It all combines nicely.

I have a 12 volt system and run my rooftop air conditioner. I have 640 watts of PV on the roof and 640 watts of PV deployed on the ground. With all that I can run the air conditioner for three to four hours with some input from the 560 Ah battery bank. If I want to go longer I'll fire up the on-board generator.

 

[idreadnought]

One air conditioner on a 5th wheel takes 1800 watts when running. Do you plan to use the microwave?

I built an off grid system for my moms 5th wheel. Wow, what a learning experience. I started with a mpp solar 5048 Charge controler inverter. With that unit it would overload the inverter when the ac started unless there wasn't anything else on. I had to install a soft start on the ac to get it to work. This was because the 5048 is actually 2 120v inverters synced to create split phase 240v. But each leg of the split phase only produces 2500 watts. Since the ac is only 120v it was difficult to power it with that inverter. Microwave, same issue.

I didn't mess with the installed 12v system at all. The lights and some other stuff run off 12v. The 5th wheel has a charge controller for the 2 12v batteries and supplies 12v when connected to Grid or off grid AC power. It was a helpful backup also if there was a issue with the inverter. At least all the lights still worked when AC power went off.

Look for a AIO unit. Many have options for charging 24/48v batteries with either solar or generator. I know the mpp solar 5048 did.

I also recommend going bigger than a 3000 watt inverter. For everything but ac and microwave it would work perfect. But both those items have a huge startup current. Also consider a low frequency inverter. Some of those have a 3 times surge rating (6kw inverter 18kw surge).

My goal with my moms off grid system was for her to use it like a connected to grid home. I didn't want her to have to budget electricity. And she has 2 of those uber low effeciency rooftop air conditioners.

First system. 3600w solar panels, Mpp solar 5048 inverter, and 8 Kw of batteries. Nope, not enough of anything.

Second system Added 2000w solar panels (5600w), added 12kw of batteries, (20kw) and changed the inverter to a 12kw low frequency.

Now it works almost flawlessly. Those air conditioners are the most ineffecient on the planet. Because it is a recreational vehicle, it doesn't have regulations that enforce effeciency. My mini split in my home is 18 seer, her air conditioners are around 7-8 seer. Window AC start around 10 seer for reference. Ugh I hate those AC units.

Hope this gives you some ideas. Good luck with your project

 

[RoadTurtle]

I have a decent system that works well
.
Multiplus II 12v 2x 120v - should have gone with 24v
6 12v 100ah battleborn batteries - should have gone with 24v batteries, but started with 12v and locked myself in with 12v
2 100/50 SCC one for drivers side, one for pass side. Should have gone to 150v unit
6 24v 200w panels.... this is where I have an issue. I'd like to add two more panels, and 2s2p make sense... but I have a temp issue with SCC
smart shunt
Cerbo GX

Modified aircon with microair EasyStart

 

[justinm001]

I'd suggest going 48V as it'll be easier and cheaper then using some charger for the 12V. I'm working on my 12V to 48V conversion (batteries were JUST dropped off) and one thing I'm wondering is if it makes sense to use a 12V battery with the DC to DC charger. This would allow me to use more 12V power than the charger is capable of and sorta allow my 12V to work as a battery backup type system if my 48V dies. For me I have lights, water pump and router/pc/wifi as well as the CerboGX that all run 12V so it'll be nice to get an alert that my 48V has low voltage before it turns off.


Also instead of DC to DC charger they make things like this that'll work. I've used a 12V to 12V one on FLA to reduce LED flicker and use a 12V to 48V for starlink, haven't done the 48v to 12V though.

https://www.amazon.com/Converter-Voltage-Regulator-Transformer-Waterproof/dp/B09G2WCHG6/ref=sr_1_1_sspa?keywords=48+to+12v+voltage+reducer&qid=1685979309&sprefix=48+to+12v%2Caps%2C109&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExSFc4Tk5BUFlWR1FWJmVuY3J5cHRlZElkPUEwMzk0NzM2MzYwSUdPRTRLMkoxSyZlbmNyeXB0ZWRBZElkPUEwNjgxODQ4NkZETkFZUE41WUZJJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[fastline]

I think one direction I am looking at is keeping the small 12V battery bank and the OEM 12V battery charger that runs off the AC, then use the 48V bank only for AC power and keep that as a discrete system. This would hold the 12V voltage up where it should be and if I lose AC I still have 12V functionality.

My concern with a DC/DC converter is what voltage they will actually be at. I do believe having at least a small 12V battery would be smart. I would probably just keep a pair of GC2s for the 12V config.

As for what I can run with the AC inverter system, I am not too worried about 'running everything' like full shore power. I will only be able to run one AC and fine with kicking it off to run the micro for a couple minutes.

One of the factors I have to deal with is the new rig has a residential fridge, which I did not want. I like being able to run one on LP. Right now I have no idea what sort of duty cycle it will run at and all that heat is just pumped right back into the space.

 

[justinm001]

I think one direction I am looking at is keeping the small 12V battery bank and the OEM 12V battery charger that runs off the AC, then use the 48V bank only for AC power and keep that as a discrete system. This would hold the 12V voltage up where it should be and if I lose AC I still have 12V functionality.

My concern with a DC/DC converter is what voltage they will actually be at. I do believe having at least a small 12V battery would be smart. I would probably just keep a pair of GC2s for the 12V config.

As for what I can run with the AC inverter system, I am not too worried about 'running everything' like full shore power. I will only be able to run one AC and fine with kicking it off to run the micro for a couple minutes.

One of the factors I have to deal with is the new rig has a residential fridge, which I did not want. I like being able to run one on LP. Right now I have no idea what sort of duty cycle it will run at and all that heat is just pumped right back into the space.

This is how my coach came with a 12V system connected to an ac to DC 12V charger as it was a commercial coach that just ran off the genny. The 12V batteries were dead likely for years.

I added a residential fridge from my old coach and it's amazing and uses a ton less power than absorption fridges like ones that run on LP. I keep it on 24/7 and never see my total coach wattage above like 100w and I'm sure most of that is other devices. Absorption fridges are a lot more, waste a bunch of space behind and can't keep stable temps (fluctuate based on outside temps).

 

[fastline]

This is how my coach came with a 12V system connected to an ac to DC 12V charger as it was a commercial coach that just ran off the genny. The 12V batteries were dead likely for years.

I added a residential fridge from my old coach and it's amazing and uses a ton less power than absorption fridges like ones that run on LP. I keep it on 24/7 and never see my total coach wattage above like 100w and I'm sure most of that is other devices. Absorption fridges are a lot more, waste a bunch of space behind and can't keep stable temps (fluctuate based on outside temps).

Not sure if your compressor fridge is 12V. Many are, which basically run a lower power compressor system. I've tested other fridges at around 300W when running but have not tested this one just yet.

I think a lot of people have fought with absorption fridges but mine has done well for me. I have found that most never clean the stack and it made a HUGE difference in mine! It was staying lit non stop. Now it cycles and my drinks usually have ice in them after a few hrs. BUT, they are small!

I am stuck with the AC compressor fridge so I will make it work. I will get a test on it soon. It has a dedicated 12V, 1000W AC inverter that I will probably disable since I should have 24/7 AC power. But if I get in a pinch, I can use it. It has an internal ATS so it passes AC through when available, and switches to inverter mode when AC is lost. I am hoping to just remove the 12V source to it so it stays in pass through mode. That will make it easier to enable it if ever needed.

 

[idreadnought]

In my moms 5th wheel it came with a 120v ac fridge that had a dedicated circuit to the supplied 1000w 12v to 120v ac inverter. Other items like lights, awnings, leveling, and radio, came from 12v direct from converter or 2 12v batteries.

Also, consider a soft start for the ac you plan to run. The startup would trip her inverter 25% of the time, even with small loads running. TV or if the fridge was on.

 

[fastline]

In my moms 5th wheel it came with a 120v ac fridge that had a dedicated circuit to the supplied 1000w 12v to 120v ac inverter. Other items like lights, awnings, leveling, and radio, came from 12v direct from converter or 2 12v batteries.

Also, consider a soft start for the ac you plan to run. The startup would trip her inverter 25% of the time, even with small loads running. TV or if the fridge was on.

Yeah, it is a certainty that digital soft starts will be used. No way around that. Actually, I may also supplement the bedroom area with a mini split heat pump so the big power hogs don't always have to be running and I can grab some heat as well. Actually just not having to listen to those big noisemakers would be a plus.....

 

[idreadnought]

Yeah, it is a certainty that digital soft starts will be used. No way around that. Actually, I may also supplement the bedroom area with a mini split heat pump so the big power hogs don't always have to be running and I can grab some heat as well. Actually just not having to listen to those big noisemakers would be a plus.....

I wish I had just bought a mini split and didn't rely on the rooftops. You could purchase a 24,000 btu mini split and replace the cooling of the unit. Honestly long term it would be cheaper compared to soft starts and equipment to power the rooftops. I paid 300ish for a soft start. 2x would be 600ish. MIni split maybe $1,600