Ac Solar Power Question

[Holmiej7]

Hi All!
We are in the gutting/component stage of our short bus build and I'm wondering if someone could help me out with some guidance.
We have a cat and a dog so thought it was important to get a mini split ac/heater combo. Right now we just aren't sure the route we want to go/what is best so hoping someone can help with these questions
1 - Can you use the mini split while driving powering it with the alternator or does it draw too much power?
2 - Is there an alternative for an ac/heater that doesn't draw so much from solar/batteries?
We are not looking to make it an icebox, we just need it to be comfy for our pets on the really hot days.

[fo4imtippin]

1. You can charge your 12v batteries with your alternator. A minisplit might use up to 1200watt with some loss in the inverters. In order to keep up with just a minisplit, your alternator would need to put out 100a of charging. Some buses have 130a alternators, some busses have 300a. The bigger sustained load that you put on your alternator, the shorter lifespan it may have. You also have to ensure if you are running lithium to add DC-DC converters or management systems to keep your alternator and lithium safe. That said, mini splits can spin down to 300w and run. On the road, if its all you've got and you need to run it, it will likely be at full speed. My bus came with 2 80k BTU AC's as it needs much more capacity while running down the highway. A minisplit wont be great with high temps on the road.


2. A mini split or inverter wall unit is the best for efficiency while parked. An engine driven A/C compressor is best for while the engine is running. I would not suggest to idle your engine while parked to power your inverter (very expensive hours on your engine). If you don't have enough solar, batteries, shore power to run your A/C while parked, then i suggest a 2000watt inverter gas generator. They are about $400 and sip fuel.

[TheHubbardBus]

6-window short bus here, 2 adults, 3 dogs, 1 cat, same concerns.

Everyone's wants / needs differ, but we ultimately came to the conclusion that the compromises (and cost) required to make off-grid A/C 'doable' weren't worth it for us.

We would have had to use the entire roof space for panels (we wanted / needed room up there for other things), we would have had to delete/replace windows (we wanted to keep all the windows), we would have wanted to insulate even better than we did (which was quite well), we would have had to invest in a much larger battery bank, etc. And even then - if we had done it all - we wouldn't have much power for anything else when A/C was needed, and we'd always be one mechanical failure - or a couple cloudy days - away from being in a bad spot.

Ultimately, we designated our house A/C for 2 specific functions: To allow us to stay long term in a warm spot when connected to shore power, or when boondocking, to run off generator power long enough to weather short-lived unexpected / unseasonable temperature fluctuations in an otherwise-temperate locale.

Ultimately the most important part of our system is protocol... "dont ever be anywhere it's too hot (for our critters) to live without A/C". One irony in powering an A/C off roof-mounted solar is you have to park in the sun for it to work.

[HamSkoolie]

Originally Posted by TheHubbardBus

6-window short bus here, 2 adults, 3 dogs, 1 cat, same concerns.

OMG we have a 40' and two cats and aren't sure it's enough room to comfortably add a dog.

Originally Posted by TheHubbardBus

Ultimately the most important part of our system is protocol... "dont ever be anywhere it's too hot (for our critters) to live without A/C". One irony in powering an A/C off roof-mounted solar is you have to park in the sun for it to work.

We plan to follow the temperate zone but also want the capability of enduring heat or cold so we're planning TWO mini splits (front and rear).

But we're also spending a good chunk on the solar system (approx 25% of the build cost) with 10.24kWh of lithium, 2500+/- watts of solar, and almost $2,000 in charge controllers and inverter/charger/transfer switch. We also have 40' of roof for all those panels.



For the OP.

Do some research on using mini splits for heat. You may find, especially if your rig is diesel, that a diesel "parking heater" is more efficient and effective (we're installing two).
Also, you might consider a window AC unit if you have traditional square skoolie windows. They're cheap, available just about anywhere, and the right type can be installed inside the shell of the vehicle so that it can be left in place and in use while driving.
As for running from an alternator while underway, you'd want to install a secondary alternator just for the "house" so that your chassis electrical isn't compromised and ends up stranding you.
Better would be more battery and solar.
Every build is unique and a balancing act of compromises between space, budget, personal needs and limitations, and the all important design requirements.


As for having to park in the sun to use solar, we plan to bring our own shade with us..... our solar and decking to keep the bus roof shaded, the walls will be well insulated, the windows covered with solar reflective tint film, and lightweight shade awnings as needed.

[TheHubbardBus]

Originally Posted by HamSkoolie

OMG we have a 40' and two cats and aren't sure it's enough room to comfortably add a dog.

Our original reasoning for an RV / mobile home / van conversion was so we could get out with our critters. We've always had so many it was essentially a work-from-home job just caring for them. And since we couldn't roll with that many at any one time that meant we never went anywhere. This is the lowest point numbers-wise we've been at in quite some time, unfortunately. We've lost 2 over the past 2 years, hoping to get the bus done before they passed. But yeah, it will still be crowded. Our goal is to spend as much time outside the bus as possible. We have lots of 'crowded vehicle with animals' stories from times past. They're always great memories once the initial trauma begins to fade

You can add a dog no problem. The cats you just arrange vertically

[DeMac]

The following info has been posted to protect your glass, not your pets.

https://www.animallaw.info/topic/tab...#google-search

31 states have laws that either prohibit leaving an animal confined in a vehicle under dangerous conditions or provide civil immunity (protection from being sued) for a person who rescues a distressed animal from a vehicle.

Recently, about 14 states have enacted laws that allow any person to rescue a distressed animal (AZ, CA, CO, CT, FL, IN, KS, LA, MA, OH, OR, TN, VT, and WI). These laws functions to limit the civil or criminal liability of the person for damages resulting from the forcible entry of the vehicle. Indiana is the first and only state to require the person, who forcibly enters a vehicle to rescue an animal, to pay half the damages.

It's just fun to break school bus windows and every karen wants to be a hero. We say ha, because animal lovers are funny, but they don't always laugh it off. The pet also provides potential thieves an actual legal defense, while we get zero restitution for the "Breaking" part of the B&E.

[TheHubbardBus]

Good info (as always) & food for thought, DeMac.

I'm torn on this issue. Would I break someone's windows out if I was certain it was necessary to save an animal? Absolutely. It's the knowing that can be tricky.
Some situations are obvious. Most are not.

I'd think that a reasonable person would look at an RV / mobile home with curtains & obvious provisions for air conditioning quite a bit differently than a passenger car with nothing inside but someone's pet gasping for breath in 140-degree air. I know I sure would. But I realize not everyone thinks the same.

Best bet IMO is to make common-sense choices that preclude your animals ever actually being in danger. Like maybe not leaving them alone at any time when an air conditioner or heater (which could fail out of the blue for any number of reasons) is required to keep them alive. Personally, we don't plan on ever leaving our pets alone at any time regardless of the environment. Our entire Raison de Etra is to share adventures with them. If our pets can't go where we're going we don't want to be there.

FWIW, and to get back a little closer to the OP's original concerns, in any environment where A/C might be necessary at some point in time, I wouldn't feel comfortable with only a house A/C. 2 is one, 1 is none, but if you had to roll with only 1, I'd think an engine-driven A/C system would be the best bet.

[HamSkoolie]

Originally Posted by DeMac

The following info has been posted to protect your glass, not your pets.

https://www.animallaw.info/topic/tab...#google-search

31 states have laws that either prohibit leaving an animal confined in a vehicle under dangerous conditions or provide civil immunity (protection from being sued) for a person who rescues a distressed animal from a vehicle.

Recently, about 14 states have enacted laws that allow any person to rescue a distressed animal (AZ, CA, CO, CT, FL, IN, KS, LA, MA, OH, OR, TN, VT, and WI). These laws functions to limit the civil or criminal liability of the person for damages resulting from the forcible entry of the vehicle. Indiana is the first and only state to require the person, who forcibly enters a vehicle to rescue an animal, to pay half the damages.

It's just fun to break school bus windows and every karen wants to be a hero. We say ha, because animal lovers are funny, but they don't always laugh it off. The pet also provides potential thieves an actual legal defense, while we get zero restitution for the "Breaking" part of the B&E.

YEP, the perils of "democracy" when one considers that half the population is of below average intelligence and is allowed to vote.
The key words and phrases here are "dangerous conditions" and "distressed animal". Most of these laws also have exceptions (unfortunately lazy legislators sometimes only refer to another section, often one that provides for K9 police car requirements) and specific requirements before Karen or Ken can lawfully break your property.
Thankfully, our bus windows are high enough and dark enough that most will never know. Just be sure to put up a barrier to prevent your critters being seen from the door and front windows.

If the AC is on with the pets inside, anyone breaking my glass will be sued in civil or small claims court. This is why our 360 degree "dash" cam system will be powered on the house side of things. It will ALWAYS be on to show what happened.

[Holmiej7]

Originally Posted by TheHubbardBus

6-window short bus here, 2 adults, 3 dogs, 1 cat, same concerns.

Everyone's wants / needs differ, but we ultimately came to the conclusion that the compromises (and cost) required to make off-grid A/C 'doable' weren't worth it for us.

We would have had to use the entire roof space for panels (we wanted / needed room up there for other things), we would have had to delete/replace windows (we wanted to keep all the windows), we would have wanted to insulate even better than we did (which was quite well), we would have had to invest in a much larger battery bank, etc. And even then - if we had done it all - we wouldn't have much power for anything else when A/C was needed, and we'd always be one mechanical failure - or a couple cloudy days - away from being in a bad spot.

Ultimately, we designated our house A/C for 2 specific functions: To allow us to stay long term in a warm spot when connected to shore power, or when boondocking, to run off generator power long enough to weather short-lived unexpected / unseasonable temperature fluctuations in an otherwise-temperate locale.

Ultimately the most important part of our system is protocol... "dont ever be anywhere it's too hot (for our critters) to live without A/C". One irony in powering an A/C off roof-mounted solar is you have to park in the sun for it to work.

Thanks so much for the info. I really appreciate it. What kind of ac unit did you decide to go with? The window ac or the mini split?
I believe we have settled on some solar and then the ac will be used only when plugged in to a shore hook up. Then we will get some fans and small cool water "animal ac" units that don't draw much.
Cheers
jamie

[TheHubbardBus]

Originally Posted by Holmiej7

Thanks so much for the info. I really appreciate it. What kind of ac unit did you decide to go with? The window ac or the mini split?
I believe we have settled on some solar and then the ac will be used only when plugged in to a shore hook up. Then we will get some fans and small cool water "animal ac" units that don't draw much.
Cheers
jamie

Jamie,

Once we decided it wasn't practical (for us) to build a system capable of powering A/C off-grid + long-term, it opened up less-efficient options. We went with a rooftop A/C (coleman mach 8 roughneck 15K btu), in part because aside from framing the penetration it didn't require anything to mount the external bits to / on. We also figured (unproven) that RV A/Cs, as well as the specific A/C we chose, would have a better chance of standing up to travel/vibrations than something meant to be installed in residential settings. Overall we're pleased so far based on just running it during construction, though it is a little loud (especially on high cool), it is significantly less efficient compared to a mini-split, and dealing with the roof curvature was a bit problematic. FWIW I wouldn't go lower than 15K btus in a bus our size set up similarly (OEM windows but good insulation). Real rough guestimate, but I'd say we're probably good for a 30-degree delta or so. Once it gets past 100 outside, it's running constantly. Big part of our future plans is removable windows insulation, and that will help when needed. But still I wouldn't want to go smaller.

We didn't want a window unit primarily due to aesthetics, though honestly it's probably one of the few ways we could have cooled at least a portion of our bus with a reasonable solar system considering how small you can go with them in terms of power consumption. A small unit probably wouldn't cool the whole bus, but if you could partition off 1/2 to 1/3, I think that would be a doable 'hot weather hole up' solution.

You say 'cool water' animal A/C... do you mean an evaporative cooler? If so you may wish to consider the impact pumping humidity into your bus may have. Still way better than dead animals but it could potentiate mold issues. We considered an evap ourselves (instead of the A/C), but ended up abandoning the idea for this reason.

[Holmiej7]

Ahhh thank you so much. There are sooooo many options. Sometimes it makes my head spin. I appreciate you taking the time so much

[HamSkoolie]

Evaporative coolers do indeed put moisture into the air but if operated properly it's not an issue.

When I wasa a young buck I rented a couse in the country for $200/mo. It had a wood stove (no problem, I worked at a lumber mill) and a swamp cooler. Nothing else.
I put a portable radiant heater in the bathroom and brought waste wood home from the mill whenever the chipper clogged. This was my sole source of wood and I'll tell you what, kiln dried pine lights easily, burns hot, and keeps you warm running out to bring in more to feed the fire. LOL
In the summer I had an evaporative cooler and the 1970's shag carpet was constantly damp feeling and the house was muggy. That's because I ran it improperly and didn't know any better.
Today, I have electric wall heaters, a wood insert, and a swamp cooler.
Electric heat is used to warm up the bathroom. Wood is burned when up to keep the house warm. And an electric blanket is used when asleep.
And the swamp cooler?
There's nothing damp or muggy about my house. While not '70's shag, we do have carpet and it's not damp feeling. BECAUSE THERE IS A PROPER WAY to run an evaporative cooler.


1) get the pads wet and the blower sending cool air into the house.
2) grab a single sheet of toilet paper
3) open a window in the furthest room from the cooler that you want to cool
4) place the sheet of TP on the window screen
a) if the TP falls off close down some window opening
b) if the TP plasters itself to the screen, open the window more
1) if the window is fully open, open a window in another room you wish cooled
5) Repeat all steps in 4 until the TP just barely stays on the screen and is in danger of falling.... it should "flutter" a bit".


You now have sufficient ventilation for the swamp cooler to provide the maximum benefit. If winds come up and blow into a window, close it down a bit or completely depending on how severe the wind is.
We LOVE evap cooling but it requires a lot of water and so we ruled it out.

[Holmiej7]

Amazing. Wow thanks for all of the input and direction
Cheers!!!

[flattracker]

if you can add a second alternator to the engine on you bus, 250 amps - 300 amps, then you could run your mini-split going down the road. I recently learned that alternators on newer vehicles have output voltage controlled by one of the computers in the vehicle. I haven't yet learned if there is a common protocol to make this work, but in the future I may use a modern second alternator that has computer controlled output voltage. Having this capability would potentially make using lithium iron batteries work for my design.
Has anybody on the forum looked into this?

[fo4imtippin]

Originally Posted by flattracker

if you can add a second alternator to the engine on you bus, 250 amps - 300 amps, then you could run your mini-split going down the road. I recently learned that alternators on newer vehicles have output voltage controlled by one of the computers in the vehicle. I haven't yet learned if there is a common protocol to make this work, but in the future I may use a modern second alternator that has computer controlled output voltage. Having this capability would potentially make using lithium iron batteries work for my design.
Has anybody on the forum looked into this?

I'm planning on using one for my 48v alternator. Balmar makes one for 12v as well.


https://balmar.net/multi-stage-regulators/

[Veloc]

Originally Posted by flattracker

if you can add a second alternator to the engine on you bus, 250 amps - 300 amps, then you could run your mini-split going down the road. I recently learned that alternators on newer vehicles have output voltage controlled by one of the computers in the vehicle. I haven't yet learned if there is a common protocol to make this work, but in the future I may use a modern second alternator that has computer controlled output voltage. Having this capability would potentially make using lithium iron batteries work for my design.
Has anybody on the forum looked into this?

It's not as high tech as all that. In the olden days the regulator was built into the alternator, or was a separate piece, and the regulator automatically controlled alternator output according to the vehicle's electrical needs. Modern ECM controlled alternators just moved the regulator control to the ECM, the intent being to only run the alternator when slowing down and use the battery to provide electrical power. Their thinking is to save fuel by only running the alternator when the battery is low, and by trying to do all charging under low/no load conditions when engine power isn't being used to move the car like when slowing down or going down a hill. All that complexity and it maybe saves a tenth of a gallon at the expense of batteries being deep cycled more, which causes them to fail sooner.

But for your use, a DC/DC charge controller that can accept power from an alternator and feed lithium should be able to manage. Renogy apparently has this ability.

[flattracker]

Thankyou fo4imtippin for the info. I will be looking into their alternators. The 9 series model looks like what I could use. The 310 amp model looks like the Leece Neville alternators Crown used.
The fact that they support LiFeP04 batteries is important.