diy solar

diy solar

Solar power mini split vs regular 120v AC

C

Cardude

New Member
Joined
Jun 25, 2023
Messages
92
Location
Texas
Son is wanting to rig up an old Snap On step van for a “moto camper” to live in at his job site and store his motorcycle.

He has a question about running a solar hybrid mini split with dedicated panels vs just building out a solar system with batteries and running a 12k btu 120v mini split off the inverter.

To me, since he’s starting from scratch it seems like the battery and inverter system makes more sense, but I don’t know how big of an inverter he needs and how much battery AH needs to run the mini split a few hours each night.

Also, should he get a DC fridge or just run a cheaper AC fridge off the inverter as well?

Thanks for any help and ideas. I have a solar-hybrid AC mini split I installed in my garage, so that’s why he was thinking about one of those.
 
Personally, I’d just go the AC/battery route as if one wants to run overnight in either situation they need some battery available.
But I also dont have first hand experience with a DC powered unit.
My fridge is DC/propane and it works fine but they are typically pricier
 
Fridge depends on how much storage he needs.
12V fries are available in the 150 to 700 range in various sizes.
The ac type, obviously are basic sizes...
Id choose ac unless I needed small.
In my van I use a DC fridge for daily driving.
In my suburban, I run an inverter and use a dorm fridge on trips.

Solar minisplit seems silly if ya need night time cooling or heating...
 
Battery and inverter setup for sure. The regular 120v mini split is much cheaper and he's going to need a battery and inverter anyway.
 
Supervstech said:
Fridge depends on how much storage he needs.
12V fries are available in the 150 to 700 range in various sizes.
The ac type, obviously are basic sizes...
Id choose ac unless I needed small.
In my van I use a DC fridge for daily driving.
In my suburban, I run an inverter and use a dorm fridge on trips.

Solar minisplit seems silly if ya need night time cooling or heating...
Click to expand...
He likes to cook and would like to have close to a house size if possible, but if that would draw to much on the batteries he can go to the smaller Chinese Danfoss type compressor fridges I suppose. I have one of those in a little trailer and it works well and seems to be pretty efficient, just pretty small.

What’s the best inverter/charger setup, and what batteries are the best to use these days without breaking the bank? I’ve only used lead acid/AGM batteries so not knowledgeable on the latest batteries that would be needed to power a mini split.
 
I like the simplicity and efficiency of a DC mini split hooked directly to solar panels. But the lowest cost option seems to be a small U-shape window A/C with an inverter or all-in-one and a small battery. You can use the inverter for other things, e.g. a microwave or some random power tool you borrow in a pinch or whatever. And if you have a compressor fridge you pretty much need a battery anyway. You can also upsize the battery and run the A/C at night if needed. The inverter/battery approach is just more flexible overall.

Even with an inverter you might consider a DC fridge. This lets you keep the inverter turned off most of the time and avoid idle consumption drain. But large-ish (e.g. 10 cu ft) DC compressor fridges seem to be $1000 and up. You can buy the same size 120V "apartment fridge" for around $300 or pick up a good used one for even less.

If he's going to have propane onboard he could consider an RV-style absorption fridge. Most will run off 12V as well, if you have sunlight to burn, but they consume 3-5x as much electricity as compressor fridges so you wouldn't want to do that 24x7.
 
Doggydogworld said:
I like the simplicity and efficiency of a DC mini split hooked directly to solar panels. But the lowest cost option seems to be a small U-shape window A/C with an inverter or all-in-one and a small battery. You can use the inverter for other things, e.g. a microwave or some random power tool you borrow in a pinch or whatever. And if you have a compressor fridge you pretty much need a battery anyway. You can also upsize the battery and run the A/C at night if needed. The inverter/battery approach is just more flexible overall.

Even with an inverter you might consider a DC fridge. This lets you keep the inverter turned off most of the time and avoid idle consumption drain. But large-ish (e.g. 10 cu ft) DC compressor fridges seem to be $1000 and up. You can buy the same size 120V "apartment fridge" for around $300 or pick up a good used one for even less.

If he's going to have propane onboard he could consider an RV-style absorption fridge. Most will run off 12V as well, if you have sunlight to burn, but they consume 3-5x as much electricity as compressor fridges so you wouldn't want to do that 24x7.
Click to expand...
I had not thought of an inverter U shaped window AC. Is it about as efficient as a mini split?
 
The Midea can use as much power as a standard window shaker when on high, but with the variable speed compressor it can slow down a lot to maintain temperature. I wish it was a real heat pump with a heat mode. Our 12k Midea is running off of our inverter as I type this and cycling between 150-250 watts to maintain 72°.
 
Simplicity of a Midea is going to win hands down even if it’s 10-20% less efficient compared to the most efficient mini split (seer2 >25)
 
Last edited:
StuBoston said:
Battery and inverter setup for sure. The regular 120v mini split is much cheaper and he's going to need a battery and inverter anyway.
Click to expand...

Yeah totally, and the problem with those solar powered mini-splits is they have to 'own' all their solar panels they're connected to, so that whatever percentage of precious roof real estate is owned by the one load only, and then how to charge your main batteries? I would rather keep the power harvest, storage, and transfer generic, so it can be centrally stored, then allocated anywhere to any load as the user chooses.


The captain's like, 'Scotty, I need more power to the engines, and I need it now!', and Scotty says, 'I'm sorry captain, but I can't divert any power from the HVAC to the warp systems, just can't do it'...
 
Last edited:
Yeah, only thing is you have to cut a Midea-sized hole somewhere to slide it through, because unfortunately there are no fittings in the refrigerant lines between the two sides so it can't be separated into two separate sections without custom work and at that point you're time/money ahead to buy a bare-bones mini split for $450-600 anyway. So yeah they're great for the money and simplicity but you do need to put a big hole in the van somewhere.

I have both 8k and 12k versions of the U-shaped unit. They're great for what they are. But at 300-400$ you're only about $200 more bucks away from the mounting flexibility and 'no giant hole in my vehicle' of a real mini split, PLUS the real mini split will do heat. So the Midea is not necessarily a slam dunk unless you're A: putting it in an existing hole (aka window), or B. you dont mind cutting and then partially refilling a hole big enough to slide it through as a 'wall' installation.

On the bigger topic, i would 100% do battery and inverter to power the air conditioner and fridge and whatever else. Even a full size house fridge does not take much battery to run from sundown to sunup, especially in a mild ambient temp environment and with less than a full family of people opening and closing it all the time. It's almost a non-issue. A 12v 100ah battery will cover it overnight with tons to spare, and i dont think anyone is really doing a vehicle system smaller than 100ah anyway.
 
The van is a bread/food truck style right? Mostly flat sides right?

A little fabrication should be the easiest thing.
 
Well, the big problem is that if the entire rear wall is either a rollup or fold-down door, you're not going to be sticking a window unit through that, and you can't stick it out the sides either. You'd HAVE to run it backwards out the front of the box over the cab, and at that point the condenser fan would be fighting the ambient airflow when you drove down the road.

Although, i do suspect that the midea PWMs its fans based on refrigerant temp or pressure, so if you were driving down the road and the condenser was adequately cooled it may not even try to run the condenser fan, in which case mounting it 'backwards' might be completely fine!! Or, you just might never have it on while driving either. But in my ~23' rv i do find the cab ac can't keep the whole box cool while driving in hot climates, so i do run the 5000btu window unit i stuck in the back wall while driving. I run it off my 12v inverter, so basically off the alternator, while driving. My alternator and wiring to the inverter are not really sufficient to run the ~1300w rooftop unit while driving without simultaneously draining down the batteries (~460ah lifepo4, maybe ~150ah usable from FLA), but it can be done for a while.
 
Doggydogworld said:
I don't know exactly. Midea is inverter-based and claims to be the first window A/C to win the Energy Star most efficient rating. This article discusses some of the pros and cons.
Click to expand...
It’s an interesting idea, but will be harder to find a place to mount I think since it’s not split. I can get a cheap 12k mini split for around $700,
Vigo said:
Yeah, only thing is you have to cut a Midea-sized hole somewhere to slide it through, because unfortunately there are no fittings in the refrigerant lines between the two sides so it can't be separated into two separate sections without custom work and at that point you're time/money ahead to buy a bare-bones mini split for $450-600 anyway. So yeah they're great for the money and simplicity but you do need to put a big hole in the van somewhere.

I have both 8k and 12k versions of the U-shaped unit. They're great for what they are. But at 300-400$ you're only about $200 more bucks away from the mounting flexibility and 'no giant hole in my vehicle' of a real mini split, PLUS the real mini split will do heat. So the Midea is not necessarily a slam dunk unless you're A: putting it in an existing hole (aka window), or B. you dont mind cutting and then partially refilling a hole big enough to slide it through as a 'wall' installation.

On the bigger topic, i would 100% do battery and inverter to power the air conditioner and fridge and whatever else. Even a full size house fridge does not take much battery to run from sundown to sunup, especially in a mild ambient temp environment and with less than a full family of people opening and closing it all the time. It's almost a non-issue. A 12v 100ah battery will cover it overnight with tons to spare, and i dont think anyone is really doing a vehicle system smaller than 100ah anyway.
Click to expand...
I agree on going with the mini split. I’ve installed a few and have the tools, so that’s kind of a no brainer except for where to locate the compressor unit on this step van. Might try to mount it inside in the rear corner of the van in it’s on sealed off from the living area box with big vents for the intake and exhaust.

Think a simple 5kw system like this would be enough for his van, to run the fridge all night and the mini split a few hours at night? I sure like the simplicity and how clean it looks. He would also want to run the mini split during the day in hot months because of a pet however, so he might need more battery. The Pioneer 12k btu 120v mini split I’ve installed before pulls max 10amps and usually lower, like around 7 I think.
 
So, my context is this: I can air condition a ~150 sqft bedroom, or a similar size RV, on ~2kwh a night. It's highly variable with conditions, but in general YES a 5kwh battery will let you cool a small space overnight plus run a few odds and ends. In the hottest ambient conditions it will probably be borderline and force you to raise your temp setpoint to avoid killing the system overnight. I see your location is Texas so not sure where this van is sleeping but in San Antonio it can stay well above 80f all night in the summer, but most other places in USA are nothing like that.. lol
 
Yes we are in Texas, and my son works in Louisiana at times so it’s really hot and muggy in the summers obviously.

I’m really unfamiliar with all the new fangled batteries and AIO thing like Will has on his video. I think he said another rack battery could be added if needed?
 
To power a full size fridge, and a minisplit in TEXAS... you are going to need 10kWh battery minimum. I RECOMMEND YOU GUT THE TRUCK AND HEAVILY INSULATE THE CABIN.
You will also need a generator to charge the batteries.
Not enough space on a van roof to recharge with solar.
Figure average 600W minisplit, and 120W fridge... figure 33%duty cycle and you get 6kWh some days the mini is going to be 100% duty cycle for parts of the day.
12K could be too large, if you get the insulation well, and the panels on the roof do a good job of shading the van.
 
Supervstech said:
To power a full size fridge, and a minisplit in TEXAS... you are going to need 10kWh battery minimum. I RECOMMEND YOU GUT THE TRUCK AND HEAVILY INSULATE THE CABIN.
You will also need a generator to charge the batteries.
Not enough space on a van roof to recharge with solar.
Figure average 600W minisplit, and 120W fridge... figure 33%duty cycle and you get 6kWh some days the mini is going to be 100% duty cycle for parts of the day.
12K could be too large, if you get the insulation well, and the panels on the roof do a good job of shading the van.
Click to expand...
Thanks for the info. This is a box type delivery truck with an 18’ box, so room for like 2500w of solar up there I think. So if he just has the fridge running during the day when he’s at work and that much solar, think it would be enough to run the mini split for maybe 5-6 hours after work with no generator? If it’s a sunny day obviously.

I’m starting to see why a 10kw battery is needed.
 
If for portable use, 12V DC output type of refrigerator is more than suitable, just look at the ingredients he needs to cook these whether he needs a lot of space to stock up, now the winter is coming, even if you have 2500W of solar energy, it does not guarantee that there is a good conversion of sunlight
 
You must log in or register to reply here.

Similar threads

HighCountry
EG4 Hybrid Mini Split 12k/24k - Wiring Question
2
Replies
23
Views
1K
timselectric
T
J
Questions on solar system build
Replies
15
Views
402
Justlivin
J
I_can_solar_it
Shopping for Eg4 Mini split through google shopping option. Free shipping.
Replies
10
Views
827
42OhmsPA
4
G
24K BTU EG4 solar mini-split sizing questions
2
Replies
26
Views
2K
Danke
Danke
B
Mini split
Replies
3
Views
279
timselectric
T
Back
Top