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OregonMan's avatar
OregonMan
Explorer
Aug 13, 2022

Powering AC unit built into travel trailer with solar?

Hi guys I am looking to get solar set up for my travel trailer. It's a 2018 model and has a fairly efficient air conditioning unit built in to the ceiling/roof. I've watched YouTube videos showing how to use solar panels and a power inverter to power a window air conditioner, but what about when the air conditioner is built into the roof of your trailer? My trailer has a "solar ready" 10amp Furrion plug but I doubt that'll be enough to power the AC unit? Is there an adapter I could use to plug the power inverter directly into the 30amp power port on the outside of the trailer that I use to plugin at campgrounds?

Thanks for any tips on powering this built-in AC unit using solar panels.

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  • valhalla360's avatar
    valhalla360
    Navigator
    Aug 14, 2022
    CA Traveler wrote:
    A air conditioner that draws 12A AC would require an inverter that draws 130A DC from the batteries and would require a large solar array, battery and inverter. Basically it's just not practical for a RV.

    Instead use a 2000W gen or larger for your 30A RV to run the A/C.


    To put this in perspective...

    12a @ 120v AC, is 1440w. Assuming a 50% duty cycle (ie: the thermostat has it running 50% of the time), you will need around 17.5 kwh of usable energy in the battery bank.
    - Lead Acid batteries can only use around 40-50% of the rated storage if you don't want to damage them.
    - Lithium can use around 80% of the rated storage.

    A 220amp-hr 6v golf cart battery is rated for around 1.3kwh...to get 17.5kwh of useable power, you will need around 26 batteries.

    You will need around 18 100amp-hr 12v lithium batteries. Still a lot of batteries to find a home for and a lot of $$$$.

    This is for modestly warm conditions. When it's hot, don't be surprised if the duty cycle is near 100%, so if you want to handle those conditions, expect to double all the numbers above.

    Of course, you need to fill those batteries if you want to use them day after day. Let's round up to 20kwh each day as you likely will run the fridge, lights and other items. A good rule of thumb is you get around 4 solar hours per day. This means for every 1 watt of rated solar cells, you will get 4 watt-hr produced. To get 20kwh, you are going to need around 5kw of solar panels. Assuming 15w/sqft, that's every square inch of roof on a 40ft RV.

    A mini-split can get some efficiency gains but if you want to just turn it on and get cool, it still needs a big battery bank.

    PS: If you get a generator, go at least 3000w, so you don't have to mess about with sometimes it works and sometimes it doesn't.
  • afidel's avatar
    afidel
    Explorer II
    Aug 14, 2022
    Maxxfan is 10 speeds.
    I've got a Nocturn computer fan that I use to cool the area under the bed, a Heng vent fan and the endless breeze. While they're not enough when it's 90 at night, for the vast majority of days in the north it's going to be enough to sleep comfortably if you don't have hookups.
  • Gdetrailer's avatar
    Gdetrailer
    Explorer III
    Aug 14, 2022
    afidel wrote:
    Gdetrailer wrote:
    spoon059 wrote:
    CA Traveler wrote:
    Not sure about a mini-split cycling down with the typical poorly insulated RV. But if a 4A 120V unit does the job then for 12V use a 11x multiplier. So 44Ah for 1 hour and 440Ah for 10 hours. For flooded batteries 880Ah with a 50% discharge would work. Thats 8 6V GC2 deep cycle batteries weighing about 500 lbs.

    Thats great - err oh wait - It's day 2 and I now have to recharge the batteries... Gens looking better...

    Ha, I get your point, but how long do you think it would take to charge that battery bank with a generator? If I'm staying in a National Park and limited to generator use during the day, it still solves my problem of having air conditioning overnight!




    120MM 12V computer case fan like above does a pretty swimmingly well job of moving air around while sipping your battery power..

    Careful selection of those fans can get you noise levels of 40 DB or less but get you 100 CFM of air movement all the while using 12W or less.. The key to quiet is to look for low RPM models under 3,000 RPM.. Of course, you will need to buy some fan grill guards for each side but those can be had for low cost also.

    While not as nice and comfy as A/C, it is an improvement over hot muggy nights with no natural air movement and no generator or additional batteries required..


    Maxxfan will move 486CFM at .48A and 36dB, much more efficient than a computer fan. If you want horizontal movement you can get a Fantastic fan in a housing called the endless breeze, not quite as efficient as the maxxfan but it will move 900cfm at 3A so still pretty power efficient. We used that while dry camping at the north rim without any solar.


    :R

    Apples and oranges..

    Computer fan = $10 or less

    Place it anywhere, no installation needed, when it breaks, buy another cheap one. They also can be easily adjusted for speed by lower the voltage or you can also buy them with a manual speed control if you like.

    Max fan = $100

    Have to remove and replace your roof vent, can't move around, when it breaks spend loads of money on new unit. Has what, two or three fixed speeds.

    Computer case fans come in a variety of versions, some draw more power some draw less per CFM. I gave a general statement on what you generally will find on computer fans and one does have to check the specs.. I do have some that draw less than .5A and have more than 150 CFM but those are high speed (6,000 RPM) fans and are around 70 DB noise level..

    The beauty of the computer case fans are they are inexpensive, meaning you can buy a bunch cheap, place them anywhere you need a breeze and run only the ones you want or need at any time.
  • Gdetrailer's avatar
    Gdetrailer
    Explorer III
    Aug 14, 2022
    pianotuna wrote:
    Gdetrailer wrote:

    A generator is still far less expensive over the long run when you factor in the cost of 2,500W worth of solar, battery capacity to handle the load and the cost of that 48V A/C unit..

    I suspect you would be in it for north of $10K US just to get 24 hr operation and that would just be for the A/C only.. Add in other normal items you want to power in your RV and I suspect you might be over $15K US.

    Makes a $1K US for a generator look better and better even if you factor in cost of oil changes and fuel for the gen.


    Gdetrailer,

    I track my expense careful Since 2009, I've spent 12,000.00 on generators and related expenses. One generator was a piece of junk that did not have rust proof screws. It did not last 3 months. One Yamaha equipped with remote electric start was stolen. The rack for that was about $200.00. I had a cage purpose built for a replacement Yamaha again with remote electric start. The cage is wonderful, but PRICEY.

    So I wish I had invested in solar. One thing that stopped me was I had not discovered my favorite battery type yet.

    On the other side of the equation, the Harbor Freight 3500 generator is more capable than the Yamaha, and costs 1/3 the price.


    Can't help with the bad choices in gens, comes with the "territory", sometimes the expensive brand names don't pan out as well as some folks think they should..

    Myself, still have the first gen I ever bought back around 2001 or 2002, 4Kw Buffalo Tools open frame Chinese Honda clone. Cost me $250 on sale at a local Mom and Pop hardware chain. Only major issues with it was the tank valve broke off while gen was in the truck bed.. Dumped about 1 gallon of gas.. Have had to clean the carb just a couple of times over the yrs and recently had to replace the starter cord..

    Spent less than $20 on the gen for repairs not including fuel and oil changes.

    Uses about .5 gallon of fuel per hr and full tank can get me 10-11 hrs of run time..

    More recently bought a 8500W HF Predator gen specifically for the house on sale for $500. Needed a gen with 240/120V to run my water well and I wanted a gen with electric start for winter time as pull starting in the winter can be a buzz kill.. So far, the HF gen has been flawless and runs everything I have thrown at it.

    Picked up a used 2KW Buffalo Tools brand open frame gen that is at least 30+ yrs old (painted red version) from a neighbor for $10.. It sat with water in the fuel tank for yrs. Removed the tank, dumped the rusty water and rust scale, pressure washed the tank, removed the carb to clean it well.. Reassembled, added some fuel and started the second pull.. Didn't need the 2KW gen but for $10 figured I have wasted a lot more on other things over the yrs.

    Folks on this forum tend to over think, over complicate and over spend.

    For the money you will spend messing with large solar arrays then buying enough exotic Lith technology batteries and all the misc stuff needed, you could buy 40 cheap open frame 4KW gens. Yes, those gens are not as quiet as a $1,500 Honda or $10,000 worth of solar but they are cheap to get into, cheap and easy to repair and cheap to replace if some one steals it.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Aug 14, 2022
    spoon059 wrote:
    Huntindog wrote:
    Don't forget that it is not feasable to charge LA batteries with a generator beyond 80% in a camping situation.

    Can't forget what I never knew...:W

    That's something else I'd have to educate myself on!


    Hi spoon,

    He means it is costly to do so. Too many hours of run time on the generator. So the cost of fuel becomes onerous.

    Of course, solar is a one time cost, so it can be used to top off batteries.

    nickthehunter

    So far there has only been one report of a failed solar panel, and it had nothing to do with a tree branch falling. I suspect if something hits hard enough to fracture a panel, that there will be other problems, such as a caved in roof.

    Theft does factor in because if I had gone solar there would have been no generator to steal. And BTW the generator was secured by a hardened steel device. But a cut off wheel makes short work of that.

    Li batteries are a good choice so long as they are not allowed to get too cold. For me they would be useless, so when my next bank is created, I'll use SiO2.
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Aug 14, 2022
    The devil is in the details and many of those haven't surfaced yet. Are 8 GC2s adeguate or practical? Lithium batteries can be fully charged to 100% and discharged to 90% and are much lighter, but still the power withdrawn has to be replaced. Is a 4A (aveage) mini split draw adequate during the summer? Other house loads, etc?
  • nickthehunter's avatar
    nickthehunter
    Nomad III
    Aug 14, 2022
    pianotuna wrote:
    Gdetrailer wrote:

    A generator is still far less expensive over the long run when you factor in the cost of 2,500W worth of solar, battery capacity to handle the load and the cost of that 48V A/C unit..

    I suspect you would be in it for north of $10K US just to get 24 hr operation and that would just be for the A/C only.. Add in other normal items you want to power in your RV and I suspect you might be over $15K US.

    Makes a $1K US for a generator look better and better even if you factor in cost of oil changes and fuel for the gen.


    Gdetrailer,

    I track my expense careful Since 2009, I've spent 12,000.00 on generators and related expenses. One generator was a piece of junk that did not have rust proof screws. It did not last 3 months. One Yamaha equipped with remote electric start was stolen. The rack for that was about $200.00. I had a cage purpose built for a replacement Yamaha again with remote electric start. The cage is wonderful, but PRICEY.

    So I wish I had invested in solar. One thing that stopped me was I had not discovered my favorite battery type yet.

    On the other side of the equation, the Harbor Freight 3500 generator is more capable than the Yamaha, and costs 1/3 the price.
    what happens if a tree branch falls on your panels and damages them? Theft / tree branch / hail / water damage (broken seal) / whatever - that’s what insurance is for. In either event, You either pay a premium every month or you self insure - I fail to see how a stolen generator factors into a cost benefit ratio vs. solar.
  • spoon059's avatar
    spoon059
    Explorer II
    Aug 14, 2022
    Huntindog wrote:
    Don't forget that it is not feasable to charge LA batteries with a generator beyond 80% in a camping situation.

    Can't forget what I never knew...:W

    That's something else I'd have to educate myself on!
  • Huntindog's avatar
    Huntindog
    Explorer
    Aug 14, 2022
    spoon059 wrote:
    CA Traveler wrote:
    Not sure about a mini-split cycling down with the typical poorly insulated RV. But if a 4A 120V unit does the job then for 12V use a 11x multiplier. So 44Ah for 1 hour and 440Ah for 10 hours. For flooded batteries 880Ah with a 50% discharge would work. Thats 8 6V GC2 deep cycle batteries weighing about 500 lbs.

    Thats great - err oh wait - It's day 2 and I now have to recharge the batteries... Gens looking better...

    Ha, I get your point, but how long do you think it would take to charge that battery bank with a generator? If I'm staying in a National Park and limited to generator use during the day, it still solves my problem of having air conditioning overnight!
    Don't forget that it is not feasable to charge LA batteries with a generator beyond 80% in a camping situation.

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