5000 BTU in a Casita

[Lapine Rider]

I currently own a converted 6x10 cargo trailer with 600 watts of solar and about 1200 watt/hours of batteries. What I love most about this trailer is that, combined with a soft-start 5000 btu air conditioner and starting out fully charged, this setup effectively provides solar powered air conditioning for the first 2-3 overnights at Wal-Mart or wherever on pretty much every trip I take. This covers my travel time to and from more often than not, so I don't have to mess with a generator-- and the related noise and risk of theft-- on the road. I like being able to do this a lot, especially since I live in hot/humid Florida, but I also am developing a powerful desire for a "real" bathroom and some of the other creature comforts of the Casita. Two things are keeping me from buying one tomorrow, and the need to run a generator overnight during hot weather on the road is the more important of the two. Besides, I'm developing arthritis, and while I already own a larger generator a 25-or-so pound 700/900 watt Ryobi propane-only generator has rapidly become my go-to unit. It'll run my 5000 btu unit without breaking a sweat, but I'm painfully aware that won't be the case with the roof unit in the 17' Casita that I'm so tempted by. So... Has anyone ever successfully mounted a 5000 btu air conditioner in a 17' Casita SD? I'm considering trying to make a plywood adapter to fit an existing window with the screen removed, so that I can lift it easily into place when needed for overnight stops while traveling. What's the most wattage of solar panels anyone's ever successfully mounted on a Casita and how did they do it? I can't use panels sitting on the ground for this purpose because the system needs to recharge while driving, and I fear that to make things work the way I want them to I need at _least_ 600 watts of panels. While in theory I could mount the battery bank in my pickup bed and connect it with a long lead, is there a good place in a Casita to install about four good-sized lithium-ion batteries and a big inverter? Thanks in advance!

[Jon in AZ]

Casita 16’ers have a factory floor-mounted window AC unit, not sure the BTU rating.

You might also consider a Bigfoot 17. They have more roof space for solar panels, more storage compartments where you might locate the batteries, and better insulation. The older ones are about the same weight as a Casita 17, although they have a larger and less aerodynamic towing profile.

A 17’ trailer is quite a bit bigger than what you’ve got. I’m wondering if 5000 BTU’s will be enough in your climate? You’re definitely pushing the envelope. Off-grid A/C without a large generator is kind of a holy grail.

One point of clarification for a non-electrical person... I’m familiar with amp-hours as a measure of battery capacity, but I’ve never heard of watt-hours. What does that mean and how does it compare to conventional batteries?

[Alex Adams]

Watts are the volts times the amperage. I assume 1200 watt hours at 12 volts is 100 amp hours.

[Jon in AZ]

...which seems very little for a lithium set-up and certainly not enough to run an A/C through an inverter for 2-3 nights- so I’m still confused.

[Alex Adams]

I'm confused too Jon. Lets assume his 5000 BTU AC runs at 4 amps AC which would be about 40 amps DC. Assuming 6 hours of night with no sun (generous I know) just to cover one night, the AC could only run about 2 hours(assume the rest of the power is eaten by the inverter). That means the AC could only run 20 minutes every hour. If the nighttime temperature were low enough and the thermostat turned up, that is possible. To do this without recharging in between for 2 nights means the AC could only run 10 minutes every hour and for 3 nights it could only run 6.66 minutes every hour. Again, I have made a lot of assumptions so YMMV.

[thrifty bill]

Hot and humid Florida = not happening. Kick the solar panels up a lot, put some on the ground, some on the tow vehicle, and you might get there.

Realize panels mounted on the trailer itself are subject to the conditions where the trailer is parked. For example, I prefer the trailer be in a shaded area, and in hot humid Florida, more so! Portable panels, or panels mounted to a tow vehicle can help in that case.

I met a guy running a small mini-split on his small camper, using solar. He had about 1500 watts of panels, trailer was covered, and he had almost 600 in portable panels too! He was also running a small compressor refrigerator.

[Raspy]

Be realistic on the theoretical solar output vs load you want to run.

On a per day basis, you'll be lucky to get 50% of the rated output from collectors lying flat on the roof of the trailer. Then while charging batteries, you'll give up about 25% to inefficiencies while charging lead acid batteries. Then the inverter will waste about 10% while running a load and converting 12v to 120v.

When converting 12 volt DC to 120 volt AC, it's not a 10 to one ratio. The inverter costs easily 10%. So figure your DC amps at 11 times the 120 volt amps.

[Lapine Rider]

Okay... My setup _does_ work. I use it several times a year. But I'm not actually doing what you guys apparently think I'm doing. First, when using this setup I'm not boondocking in the traditional sense. I'm traveling, which means my power usage during the daytime while I drive is zip, zero, nada. So every single collected watt of solar power goes towards charging my battery bank. Second, I cannot and did not claim to be able to do this indefinitely. If I start with a full battery bank, I don't have quite a full charge when beginning the second night and begin with an even lesser one the third, even in sunny weather. In my case, however, so far I've always arrived wherever I want to go by that third day and from then on use shore power. In two days or so, I'm then back to a full charge for the drive home. So effectively this setup does everything _I personally_ need for it to do. I'm also willing-- though so far in the real world this has only happened once-- to drain my bank over 50% in order to get a good night's sleep on the road. Third, the math does actually work because an air conditioner's compressor doesn't run continuously. Under most circumstances, in my tiny, extremely well-insulated trailer at night, with no sun-heating, my compressor runs maybe 10-15 minutes an hour once the temperature has stabilized. (I've never actually timed this-- it's a guesstimate.) I use a Frigidaire unit with a soft-start that, according to the product's website, pulls 450 watts (I've measured 435) with the compressor running. It's been a long time since I actually worked all of this out and I'm not certain that I recall this figure correctly, but I think the unit only pulls about 250 with the compressor off, which (at night) is most of the time. (I tend to figure everything in watts, because that's the easiest math in my own head given all the continual voltage conversions and the fact that panels, inverters and generators typically have their capacities stated in watts.) Even allowing for inverter-consumption, my battery bank is and has many times proven itself adequate to support this load overnight in real-world conditions, even when not quite fully charged. (I'll note in passing here that I received similar comments on another forum warning me it can't be done when I mentioned buying a 700/900 watt Ryobi propane generator to power this same air conditioner. Well, maybe it can't power that specific commenter's air conditioner, but... It works perfectly well for me, when it's cloudy or I want to conserve my batteries.) The biggest problem with planning a solar setup, in my still very limited experience (I've done two-- 1250 watts worth of panels mounted on my sun-porch roof are currently powering my computer, cable modem box, and 65-inch TV as I type this solar-powered reply, as they do every day all day and all night except during extraordinarily bad weather), is that every single individual uses every single appliance in a very different way, under widely variable solar conditions. Again in my very limited personal experience, you have to guesstimate your usage in a very inexact way and then trust to luck. The setup on my house was initially too small to do what I wanted and I had to add more. I'd guess that the current 1250 watt setup wouldn't be nearly enough for the ways some other folks use their TV's and computers. Or maybe some people have thirstier cable boxes than I do. (Though I doubt that-- mine is _voracious_.) If I get a Casita-- or Bigfoot (and thanks for the suggestion!)-- I'm well aware that the interior volume requiring cooling will be larger, and I suspect that my current trailer's insulation is better than a Casita's. But I'm also aware of at least one 2019 Casita 17' model that is apparently being adequately cooled (in the shade) by a 5000 btu air conditioner in 90-95 temperatures in Central Texas. My guess (and it's only a guess, though based on some limited experience) is that I'd get at least two nights out of my current-sized battery bank with a 5000 btu unit and 600 watts of panels in a Casita, and that if I went to lithium-ions (which charge more efficiently than my current lead-acids) and enlarged the battery bank a little (it will always start a trip fully charged, no matter how large it is) or added more panels I could perhaps travel in a Casita for three cool, comfortable generator-free nights. (Or maybe I could hang a heavy curtain to divide off the bedroom area and get as many as four. Who knows, until you actually perform the experiment?) So, here's my actual question again. Can anyone show me how someone's mounted at least 600 watts of panels on a Casita SD 17'? Or even more would be better. And, is there a good place to install an unusually large battery bank and inverter? My _only_ goal is not to have to deal with a noisy generator or expose it to theft while doing quick overnights at Wal-Mart or other similar places, and ground panels won't work because when the sun's up I'm mostly driving. Thanks! I do appreciate all the replies!

[Lapine Rider]

(Please forgive the solid wall of text in the posting above. For some reason this forum won't allow me to put in paragraph breaks, even via editing after posting. It's a technical glitch or software incompatiability of some kind. Sorry!)

[Glenn Baglo]

Originally Posted by Lapine Rider

(Please forgive the solid "wall of text" in the posting above. For some reason, this forum won't allow me to put in paragraph breaks, even via editing after posting. It's a technical glitch or software incompatiability of some kind. Sorry!)

Hit return key.
And, under the text block is "Edit" that can be used for a certain amount of time. You can enter returns that way after posting.

[Lapine Rider]

Originally Posted by Glenn Baglo

Hit return key.
And, under the text block is "Edit" that can be used for a certain amount of time. You can enter returns that way after posting.

Sadly, neither worked. But I'm using an unusual web-browser setup and that's probably the root of the problem. In the future, I'll know to use something else. Thanks!

[Joe MacDonald]

does your tow vehicle not charge the battery bank while driving?
that should boost your batteries quite a bit, and the remainder should be topped off by solar
Joe

[Lapine Rider]

Originally Posted by Joe MacDonald

does your tow vehicle not charge the battery bank while driving?
that should boost your batteries quite a bit, and the remainder should be topped off by solar
Joe

Mine doesn't, no. I currently have a small converted cargo trailer with a four-wire "flat" connection, and no electric brakes. Does the Casita do that? Yes, it'd surely help!

[Joe MacDonald]

you can do the same thing with your cargo trailer, run a charge line from the Battery in your tow vehicle to the rear, put on a 7 pin plug, and install a 7 pin plug on your cargo trailer, add a fuse at each pos. battery end, and voila..... a working charge system with what you have

[Lapine Rider]

Thank you! I never heard about this one.

[flowman]

Originally Posted by Lapine Rider

...
So, here's my actual question again. Can anyone show me how someone's mounted at least 600 watts of panels on a Casita SD 17'? Or even more would be better. And, is there a good place to install an unusually large battery bank and inverter? My _only_ goal is not to have to deal with a noisy generator or expose it to theft while doing quick overnights at Wal-Mart or other similar places, and ground panels won't work because when the sun's up I'm mostly driving. Thanks! I do appreciate all the replies!

You might have more luck asking on the Casita forum, but this is the best I remember seeing there, and he covered almost every available inch.


https://www.casitaforum.com/invboard...n-17ft-casita/


We're finding that we probably don't need much solar capacity for our usual camping (not planning to run A/C), but I've always thought the best way to get high capacity would be to cover the tow vehicle w/ panels (a pickup with a camper shell would provide a lot of room) and have a battery bank in the tow that would supplement the 12v in the trailer. That way we can park the trailer in the shade and charge up our batteries while we're driving around sightseeing. Good luck!

[Lapine Rider]

Originally Posted by flowman

You might have more luck asking on the Casita forum, but this is the best I remember seeing there, and he covered almost every available inch.


https://www.casitaforum.com/invboard...n-17ft-casita/


We're finding that we probably don't need much solar capacity for our usual camping (not planning to run A/C), but I've always thought the best way to get high capacity would be to cover the tow vehicle w/ panels (a pickup with a camper shell would provide a lot of room) and have a battery bank in the tow that would supplement the 12v in the trailer. That way we can park the trailer in the shade and charge up our batteries while we're driving around sightseeing. Good luck!

Thank you as well! I've considered putting at least some panels on my pickup and the battery bank and inverter in the bed, but my other non-camping uses for the truck make that problematical at best. Currently I've found an older used cargo trailer (easy to mount numerous panels on) with fairly comfortable-looking factory-installed living quarters to look at. If that doesn't work out, I'll be back to trying to figure out how to make a fiberglass unit work. Thanks to everyone for the support!

[ldsharp]

Hi Phil,
Not directly toward your posting about solar panel and battery space in/on a Casita, I offer a couple of suggestions to further your research.


1. Do some research on adding a 2nd alternator to your tow vehicle specifically for charging your battery bank while driving. In your scenario, this could replace the need for lots of solar for your driving days. From my reading, alternators will get too hot when the vehicle is idling but work just fine when driving for this purpose. This is something now being utilized in some class b units that rely heavily on their 12 systems.


2. Take a look at the higher efficiency (high SEER) AC/heat pump units that produce a lot more cooling / input power. Here's a good link for someone who has run one for over a year prior to his video/review.

https://www.youtube.com/watch?v=rjVIxqTHahY

From my experience... I owned a 17' Casita Standard for a year or so. It had a 6000 BTU heat pump installed by Casita under the front couch (about where you would stand in the shower of a deluxe). It cooled the 17' Casita just fine in 100 degree heat.


As for adding lots of batteries to a Casita - there is not much hidden floor space for batteries. The single standard group 27 fits is a little isolated compartment near the rear drivers side. You could probably add a couple just inside the rear wall and couple more in the closet but at some point the weight (even if equalized over the axle) would be a problem. Lithium based batteries would help greatly at 1/2 the weight and 2 times the draw-down but at $1k per 100 amps pretty pricey!

[Glenn Baglo]

What does adding a second alternator do to mileage?

[gordon2]

Originally Posted by Glenn Baglo

What does adding a second alternator do to mileage?

Next to nothing.

Now ask what it does to the vehicle warranty..