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[SOLVED] Power RV mini-split solar during day/grid (optional) at night/cloudy? Not grid-tie but grid-backup

cdevidal

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Sep 12, 2021
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What's a good mid-priced decent-quality solar inverter/charger for this application, such as a Growatt or MPP? What size? What's the minimum amount of battery and array size that I need? I want to run on solar as long as sun is shining, grid as a backup when not. If grid is down and sun is up, it powers it. Roof-mounting the panels is not required.

I have a 34' class A motorhome with two 13,500 BTU roof ACs. Would like to convert to a single mini-split, probably 18k BTU dual zone such as this Bosch. The brochure (page 21, BMS500-AAM018-1CSXRA / 8733942703) claims 1,547 watts, requires a 220V single phase 60Hz, min circuit ampacity 18A, breaker 25A. Big air conditioner, but we're in Florida full-time with four people inside, kitchen, thin insulation, etc.

My best guess as to what I need:
Goals:
  • Run RV air conditioner on solar while the sun shines
  • Switch to grid when it does not
  • NOT grid-tie. Allow for boondocking with partial air conditioner usage during the hottest part of the day--so no grid tie.
  • Running boondocking after solar hours is not required, to keep down the battery investment
  • Roof-mounting panels or batteries not required
  • Switch the inverter from the air conditioner to power other loads if needed--so a dedicated solar mini-split such as this isn't an option. Grid-down option to power other equipment.
 
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It looks like you’re on a right track. Just remember 220/230v single phase is different than split phase 240v. I’m thinking this euro model growatt would do it: Check this out.

I was running a 48v 12k btu mini split (no other loads) on 8 srm-24 interstate batteries (4s2p) (day use only) with four 250w obviously used, cracked vinyl panels. Both the “cheap” batteries and four panels were not recommended. But I still had like 5.5 hours of battery only operation in 95f 15% humidity if I recall correctly. The max draw never exceed 960w (EER).

My battery bank has since been updated to 300ah @ 16s/48v LFP. I can run the heat wide open all night @ 1300w (EER) with no worries on a full charge.

I realize I’m not representing all of the math required but it worked fine.

Also make sure the “cheap” flooded lead acid you get can be equalized with a grow watt. The growatt will equalize (refresh) up to 58.4v. (48v version) Some flooded lead acid require an equalization voltage as high as 16.3v per 12v battery. 60+v x 4.

After about three months of use, my srm-24 battery bank had dropped to something like 37ah usable. After equalizing to 60v with a separate charger (1.6v higher than the growatt can do) per battery manufacturer, it jumped to like 80ah. Proper battery maintenance is critical when using flooded lead acid.

This one is kind of a no brainer, but your power bill will get up and walk out the door too.
 
Going with a Growatt 5000ES European 220V (93% efficient), wiring it for the mini-split legs (no neutral needed), locked rotor on the mini-split is 16A @ 230V. For the battery bank, using 13s4p lithium-ion SPIM08HP 8Ah cells rated 200A continuous, each series has a 13s 100A BMS. Each cell is expected to see no more than 21A surge current while the motor starts and about 7.8A while running so I'm very comfortable that will be within spec. I don't need a lot of battery runtime, just enough for the surge and MPPT ramp-up. Run-time would be a few hours when I need mere seconds, so I should have plenty. And if not I can just add more SPIM08HPs.
 
Going with a Growatt 5000ES European 220V (93% efficient), wiring it for the mini-split legs (no neutral needed), locked rotor on the mini-split is 16A @ 230V. For the battery bank, using 13s4p lithium-ion SPIM08HP 8Ah cells rated 200A continuous, each series has a 13s 100A BMS. Each cell is expected to see no more than 21A surge current while the motor starts and about 7.8A while running so I'm very comfortable that will be within spec. I don't need a lot of battery runtime, just enough for the surge and MPPT ramp-up. Run-time would be a few hours when I need mere seconds, so I should have plenty. And if not I can just add more SPIM08HPs.
I'm trying to do a 220v mini split system also (220 split phase)

Did you use the Growatt 5000ES or the two SPF 3000 ?

Would you please update because I can't find a better solution either and after watching this video I don't want to use the 5000 ES

.

Did anyone have a better solution for running a 220 mini split??
 
Did anyone have a better solution for running a 220 mini split??
I’m interested in this also. 220 seems the only practical way to install an ac to replace a 15 k btu unit.

I have given up on the idea for a mini split in my 35’ fifth wheel Rv to replace a 15k BTU factory unit. To stay 110 volts, I could go with two 8 k btu units, which installing two units to replace one is not practical. If i did install those mini-splits, I think these would run at 1000 watts for both.

Right now I cam run my 15 k btu AC on solar, and when i do, it draws 1700 watts from the battery to do it. That would be a lot of work to save 700 watts. I’d still have to put my ground panels out to run the mini-spit.

I’m a bit reluctant to be the first on my block to have 220 volt installed in an RV. I’m confident I could install the solar components and circuit box correctly, but its more of when I’m not making my own power, do i trust the RV park I’m at to have the 50 amp split phase wired correctly so it does make 220 volts when hooked up. I’m confident each leg of the 50 amp makes 110 volts, but when they are connected together, not some of the older parks would take that.
 
Never trust the RV park, no matter how nice or new, to have a competent electrician on staff.
I've had more issues in "new" parks than I have in old ones, like RV's the old ones usually have the major issues corrected over time.

Buy the best ATS you can, and monitor it when you plug in and on very hot days, to make sure the voltage is right.
I've had too many instances where the power was low on one leg, mis wired or serious voltage drop when it was hot and everyone turned up their AC in the afternoon.

Our is set to just drop the park connection anytime the power is out of spec, go to battery and crank the genset when the batteries are low.

When you run multiple heads off of a single minisplit compressor, you loose efficiency. So you need to take that into account when you are planning it out.

Personally, I'm looking at the Houghton type 120v units to replace 2 of the dometics on ours. That might be an option for you.
 
I'm trying to do a 220v mini split system also (220 split phase)

Did you use the Growatt 5000ES or the two SPF 3000 ?

Would you please update because I can't find a better solution either and after watching this video I don't want to use the 5000 ES

.

Did anyone have a better solution for running a 220 mini split??
Sorry, I bought all the equipment including the 5000 ES but haven't had the time yet to connect it.

Looking at the video, I think he's right. The air con should be just fine on the Euro inverter; But I also had hoped to connect other loads as well, and so I bought an autotransformer.

And a fully-isolated transformer is outrageously expensive.

He mentions some workarounds, I'll try that or perhaps buy a different inverter.

Edit: As I think about this more, I may? be okay because none of my 110V loads are bonded to ground. I'm just running extension cords off the autotransformer, which is a portable device and would only be connected to the inverter. However I don't know if that is a shock hazard. I need to think much more at length about this and perhaps speak with the seller of the 5000 ES.

Edit again: Ah. The guy in that video (Ian) is who I bought it from in the first place. LOL. He had no such warnings on his website when I first bought it. Bummer.
 
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I’m a bit reluctant to be the first on my block to have 220 volt installed in an RV. I’m confident I could install the solar components and circuit box correctly, but its more of when I’m not making my own power, do i trust the RV park I’m at to have the 50 amp split phase wired correctly so it does make 220 volts when hooked up. I’m confident each leg of the 50 amp makes 110 volts, but when they are connected together, not some of the older parks would take that.
If it's a 50A RV it's running on 220V, that's the only way it would work. The 220 gets divided inside the RV to run each air con. If you can run both classic air cons at your RV park, it's going to be 220.
 
I’m interested in this also. 220 seems the only practical way to install an ac to replace a 15 k btu unit.

I have given up on the idea for a mini split in my 35’ fifth wheel Rv to replace a 15k BTU factory unit. To stay 110 volts, I could go with two 8 k btu units, which installing two units to replace one is not practical. If i did install those mini-splits, I think these would run at 1000 watts for both.

Right now I cam run my 15 k btu AC on solar, and when i do, it draws 1700 watts from the battery to do it. That would be a lot of work to save 700 watts. I’d still have to put my ground panels out to run the mini-spit.

I’m a bit reluctant to be the first on my block to have 220 volt installed in an RV. I’m confident I could install the solar components and circuit box correctly, but its more of when I’m not making my own power, do i trust the RV park I’m at to have the 50 amp split phase wired correctly so it does make 220 volts when hooked up. I’m confident each leg of the 50 amp makes 110 volts, but when they are connected together, not some of the older parks would take that.
Is there any reason you are not considering one of the many 12k btu 120v units that are available? I run two of the pioneer 12k units in my cabin and they work incredibly well- especially to cool.

That 1000w figure you are using will rarely be what the unit is actually running at. The only time mine runs at 1000w is when the room is hot and i am trying to cool it off quickly. I usually see a load of 400 to 600w under most conditions and it actually runs on as little as 250w while still putting out cold air once the set temp is achieved.

These min splits are the shiznit and i can't imagine trying to stay cool here in east Texas with a traditional ac system while living off-grid.
 
Both Will and Signature Solar have responded to the controversy of using the 5000 ES in the United States. I just found these videos and have yet to digest them.


 
And a few nice long threads :)



 
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The only issue when using the Euro 230 volt setup and I am not going to watch 3 videos to see if its been covered. The only issue is Some US appliances cheated and got 120 volts off the 230 volt power supply to like Stoves and Dryers by going one leg of the 230 to Equipment Ground to get the Neutral do that with the Euro and its fry time. Yes they needed 120 for the lights, clock and timers but its not right. My Mitsubishi Mini Split is 230 volts but I know you can buy Minis in 115 volts.
 
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