RV schematic w/240v subpanel - is this close?

[John Frum]

First of all—thank you!!! This was incredibly helpful for me ?
Did not know what a breakaway system was but I noticed a set of wires coming from the brake lines and wondered if there was some sort of similar mechanism! Clever… although it wasn’t hooked up ? I’ll change that in the future.

Suggest you test it with the lead acid battery as a baseline.

This makes sense now, so I’d be running a new set of wires from truck to trailer. Would there be a plug on each side, just like the 7-pin setup?

Yes.
Something like this.

https://powerwerx.com/anderson-36034p1bk-sb120-environmental-boot-source

I have a 1993 Ford F-250 diesel with 2 batteries. I’ll take a look out there later. Question though: is this something I could add in later? Or maybe plumb the wires only for now?

This can be done later but you need to have enough battery capacity to run your fridge and whatever else will be left on plus cover the breakaway system.

I am a fan of simplicity and eliminating weight. Ok, so what would testing that look like? Could I just use a voltmeter to make sure it’s getting the proper load, or is that not sufficient?

More testing than that will be required.
I would not trust this until I functionally tested all modes.
Of the cuff I would say you should trigger the breakaway system and see how it operates with the lead acid battery.
Try dragging the trailer to get a sense of the resistance maybe.
Anybody else got a good idea for a functional test that doesn't involve detaching the trailer and seeing if it sails off a cliff?

 

[DerpsyDoodler]

That’s an interesting idea—I have recently looked into a 24v -120/240v invertor, but the only one I can find is Magnum MS4024PAE, but they apparently aren’t in production right now. I’ve spent weeks sourcing components for various options….Sometimes I just wish I could order custom build electrical parts

I've read this thread through, so I apologize if I missed or forgot it, but what's the reason you're dead set on a horizontal cassette 240v 9k btu A/C unit?

 

[missadventure]

I've read this thread through, so I apologize if I missed or forgot it, but what's the reason you're dead set on a horizontal cassette 240v 9k btu A/C unit?

Because it's what I want That's it. That's the only reason. It's a choice based on space and aesthetics and preference, not functionality or simplicity or cost.

 

[DerpsyDoodler]

Because it's what I want That's it. That's the only reason. It's a choice based on space and aesthetics and preference, not functionality or simplicity or cost.

Dometic makes roof mount inverter-driven DC units. A google search turned up some roof-mount units by mitsubishi.

I personally installed a DIY 12k btu 120v minisplit and man it rocks. It consumes ~1.2kw max. I get the desire for aesthetics, but you seem to be sacrificing a lot to achieve it. Is there no way to work aesthetics in with a vertical mount mini-split? That being said, (and I couldnt find it now) but I am sure I saw a thread on this forum related to many different form-factor mini-splits (both vertical and horizontal mount cassettes). I am not sure if you've seen it (does it ring a bell?), but if not I would spend a little time going through threads on this forum related to minisplits. Not saying read-them all, but maybe scan through for some links or business plugs.

It almost looks like the only reason you're considering 240v is for the A/C you're hooked on, and it really seems to me you're sacrificing more for that specific A/C than its worth. Just my 2-cents.

 

[Seven30]

That’s an interesting idea—I have recently looked into a 24v -120/240v invertor, but the only one I can find is Magnum MS4024PAE, but they apparently aren’t in production right now. I’ve spent weeks sourcing components for various options….Sometimes I just wish I could order custom build electrical parts

I havent used this one but it seems like it might do. You may still want an autotransformer for the 120v expresso machine (I sympathize! ) ​

Growatt 3000W Off-Grid Solar Inverter 110V-120V/220-230V Split Phase Built-in 80A MPPT Solar Charge Controller, Pure Sine Wave Hybrid Inverter Work with 24V Battery Off Grid Solar Home Use ​

4.1 out of 5 stars 36

 

[missadventure]

It almost looks like the only reason you're considering 240v is for the A/C you're hooked on, and it really seems to me you're sacrificing more for that specific A/C than its worth. Just my 2-cents.

I very much appreciate the ideas. I’ve been pretty thorough with my investigation, and have concluded that every option has a trade-off: it may be noise, upfront cost, space, energy usage, etc. At this point, I think the 240v ceiling cassette mini split is the best mix of pros & cons for me. I know it’s not for everyone! Who can say if I’ll change my mind before it’s all said and done or if I’ll have regrets later. We will see.

 

[missadventure]

I havent used this one but it seems like it might do. You may still want an autotransformer for the 120v expresso machine (I sympathize! ) ​

Haha, that espresso machine must

Thanks for this! This is one of the options I originally looked at… the Growatt 24v 300K is actually 120v but is programmed to allow 120/240v split phase for parallel units (so you need 2 of them). I’ve been advised against this route due to: energy usage on the all-in-one’s, cost/space, and apparently some kind of iffy neutral (confession: I don’t understand that last reason). It turns out that a transformer is cheaper, uses less energy, and smaller, so while i haven’t ruled out the AIOs completely, a transformer is higher on my list of options at the moment.

Still—thank you for the suggestion!

 

[Rednecktek]

Anybody else got a good idea for a functional test that doesn't involve detaching the trailer and seeing if it sails off a cliff?

Yup, done this trick before on my dad's trailer:

Plug trailer into truck
Jack up 1 side of trailer, start spinning the tires by hand as fast as you can. They should free-spin if the truck is on/running.
Walk to truck and pull trailer plug.
If the brake system is working properly, the free spinning tires should come to a quick stop and you shouldn't be able to spin them by hand.
Plug truck back in and verify wheels free-spin again.

Repeat for other side of the trailer.

 

[missadventure]

Yup, done this trick before on my dad's trailer:

Plug trailer into truck
Jack up 1 side of trailer, start spinning the tires by hand as fast as you can. They should free-spin if the truck is on/running.
Walk to truck and pull trailer plug.
If the brake system is working properly, the free spinning tires should come to a quick stop and you shouldn't be able to spin them by hand.
Plug truck back in and verify wheels free-spin again.

Repeat for other side of the trailer.

This sounds fun… thanks!

 

[John Frum]

This sounds fun… thanks!

I'm imagining a hamster with a crash helmet.

 

[DerpsyDoodler]

With these electronic brakes, isn't there usually a controller unit in the cab that the driver can use to adjust or even apply the trailer brakes when they're not pressing the vehicle's brake pedal?

When doing this emergency breakaway check, may also be worth checking that the electric brakes are working, too. Even if that just means connecting the tow plug and pressing the brake pedal.

Aren't the tow plug and breakaway cable separate and distinct on these rigs?

 

[John Frum]

@missadventure how is your build progressing?

 

[HRTKD]

Aren't the tow plug and breakaway cable separate and distinct on these rigs?

Yes, they are separate systems. The breakaway system, when activated, is 100% braking. The tow vehicle varies the amount of braking action through it's connection.