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Thu Aug 24, 2023 7:36 am

One of the reasons these discussions drag on like Uncle Colm is units.

Get all your thermostat into watts. The use hours and duty cycle to determine Energy needed , in watt hours.

Now you know what you use from the battery exactly , what you need to put back in, etc.

A 5000 BTU/ hr A/C is a 1500 watt cooling capacity and will use about 500 watts of electrical power to achieve that.

The battery and solar flow from there.

Sleep 8 hours at 50% cycle…

2000 watt hours needed.

That will take 10 hours of 800 watts solar to replenish

Thu Aug 24, 2023 9:07 am

I suggest filling the roof with solar. Go with the most capacity you can for batteries vs how much space you want to consume in the cabin. Same for the portable solar panels. Forget the AC for now. Use everything else you want to. Go out and see what your consumption vs replenishment. Then decide if you can do the AC. Real world testing works much better than what the intranets tell you. I built my system for my RV over 3 years. I understand the limitations and benefits.

Thu Aug 24, 2023 4:35 pm

8h * 50% duty cycle * 500W = 2000Wh

2000Wh / 13.2V (LFP voltage) = 151 Ah consumed to run the AC for 8 hours

800W of solar is 60A theoretical input

800W / 13.2V * 10 hours = 606Ah put back into the batteries (not realistic)

however, half that time, 5 hours, at half the rated output (400W)
400W / 13.2V * 5h = 151 Ah coincidentally exactly the same as consumption

with this math, and given that full sun is typically 6 hours per day

seems feasible, even with something like a fridge going (as long as its a good one, like a BD series compressor, not some 3-way junker on 12V mode)

but, really, probably needs quite a bit more margin to be totally practical

jj is right need to get out there and start tryin' stuff

kilcash you have the right approach and right equipment in mind...your expectations are reasonable, too. you're not hoping to run the a/c 24-7 just not suffer as a sweaty mess at a camp-in festival

the wave 2 is super interesting - with its own batteries .. you can just extra capacity dedicated to the A/C .. and with enough solar could even recharge them in addition to your onboard battery ... the thing i really like about the wave 2 is that you can plumb the input and output ends of the evaporator with the included hoses .. and with that you can just try to a tailor a solution to air condition just you guys in your bed, rather than the whole bus interior .. the batteries and plumbing were the upsides to the Zero Breeze mk2 i had ... it's just the BTUs weren't enough on that one .. but the 5,100 seems serviceable on the wave2.... i've used a 6000 BTU 120VAC with success in a bus so i think it could work

give it a shot, report back :)
let us know :)

Thu Aug 24, 2023 5:21 pm

An 800 watt panel will give 200 watt average performance after dirt, shade, and cosine loss.

10 hours needed to replenish that a/c load.

800 watts rating is an awfully big panel

Thu Aug 24, 2023 11:16 pm

Abscate wrote: An 800 watt panel will give 200 watt average performance after dirt, shade, and cosine loss.

10 hours needed to replenish that a/c load.

800 watts rating is an awfully big panel
88 x 70 inch essentially 7.25 feet x 6 feet plus housing.

Fri Aug 25, 2023 5:25 am

If my bus was my everyday driver, I would put the Gilmore Enterprise air conditioner into my bus. Then I would buy a used Zero Breeze air conditioner for camping. Or you could buy a 100$ window unit with 5000 BTU's when you have an electric.

There is/was a Gilmore for sale in classified.

https://www.thesamba.com/vw/classifieds/detail.php?id=2633310

https://www.thesamba.com/vw/classifieds/detail.php?id=2334797

https://gilmore-enterprises.net/vw_bus___camper___transporter___kombi

Justin

Fri Aug 25, 2023 8:40 am

Abscate wrote: An 800 watt panel will give 200 watt average performance after dirt, shade, and cosine loss.

10 hours needed to replenish that a/c load.

800 watts rating is an awfully big panel

I have a 26ft RV and eight, 100W panels. It takes up most of the roof. One thing I did not do is take up the whole roof because I will need to service things up there and need areas to walk around.

Also, the rule of thumb is the pitch of the roof needs to be the same as the latitude. Then pointing south. When I was in college I took a solar energy course. Thus I learned the basics and still have the textbook.

Along with that, I have tested out my RV fridge running only on DC. Thus it draws right around 20A. I have a unit that can calculate the overall consumption. With my solar and batteries along with the three days of overcast and rain, I'm down a pretty good amount. It's supposed to be this way for the next few days. The solar panels help but my battery tank is on a loss. This is just running that fridge. Nothing else.

For a pop top, you better make sure the rear of the bus is pointed south. If pointed north, then you will be out of luck. There's a reason why ski slopes are on the north face of the mountain.

In the world of engineering, we have what they call, the factor of safety. Thus just don't look at the ideal numbers and use that as what you need for a project.

Fri Aug 25, 2023 9:49 am

jjvincent wrote: Abscate wrote: An 800 watt panel will give 200 watt average performance after dirt, shade, and cosine loss.

10 hours needed to replenish that a/c load.

800 watts rating is an awfully big panel

I have a 26ft RV and eight, 100W panels. It takes up most of the roof. One thing I did not do is take up the whole roof because I will need to service things up there and need areas to walk around.

Also, the rule of thumb is the pitch of the roof needs to be the same as the latitude. Then pointing south. When I was in college I took a solar energy course. Thus I learned the basics and still have the textbook.

Along with that, I have tested out my RV fridge running only on DC. Thus it draws right around 20A. I have a unit that can calculate the overall consumption. With my solar and batteries along with the three days of overcast and rain, I'm down a pretty good amount. It's supposed to be this way for the next few days. The solar panels help but my battery tank is on a loss. This is just running that fridge. Nothing else.

For a pop top, you better make sure the rear of the bus is pointed south. If pointed north, then you will be out of luck. There's a reason why ski slopes are on the north face of the mountain.

In the world of engineering, we have what they call, the factor of safety. Thus just don't look at the ideal numbers and use that as what you need for a project.

:thumbsup:

Wed Sep 13, 2023 12:17 pm

i dont think comparing the stated scenario against a RV with a 3-way fridge and 120V A/C is a fair comparison to draw conclusive answers from

those fridges have a massive constant current draw (20A in your example),
whereas a Danfoss-Secop (like the Truckfridge beloved by Vanagon people) pulls ~4A "ocassionally" when it cycles ..

the Vitrifrigo in my Riviera Bus lasted ~10 days sitting idle (with 200Ah electronically limited to about 180Ah) when i last tested it. that was with ice cream in the freezer, too.
it would have lasted 9 hours with that RV fridge.

the A/C units in question are tiny and efficient .... very analogous to the fridge example

and the solar panels i've used camping always put out more than 1/4 rated power

all that said, OP's idea is challenging but feasible - i would not be dismissive

Specifically speaking about that Ecoflow wave 2 - with external Ecoflow battery pack(s) coupled to vehicle battery bank and DC-DC recharging from solar -
seems like a very workable solution for night time use over the period of a music festival weekend
does not seem like a stretch at all

Wed Sep 13, 2023 12:54 pm

Words like “efficient “ are meaningless.

To get 3000 watts cooling capacity, How much power does the Eco flow consume , in watts?

On Edit...fixed cofefe

Fri Sep 15, 2023 5:56 pm

Lots of math and nobody mentions that when you add more solar to the roof, you get an entire shade structure that follows you everywhere you go. :)

Subtract 1mpg for the drag over 40mph, 2mpg over 60, and work out how much that cabin cooling feature saves you on AC in the long run.

Type 4 alternators aren’t good enough these days for me to recommend charging depleted leisure battery systems frequently.

Tue Jan 14, 2025 6:21 pm

.

Any updates on those who have tried solar with AC's?
Find this to be interesting..

Tue Jan 14, 2025 11:08 pm

It usually comes back in a new thread in the Spring with neither the math nor the discussion changing. It does not work

Tue Jan 14, 2025 11:56 pm

I think one thing that gets overlooked on the Ecoflow is that it is heat pump technology. It is more efficient than standard compressor based A/C. I have about 5kw solar at my home with 20kwh storage and last summer during a power outage with an overcast day I ran a 8000 btu window A/C and my standard home fridge full time during the day and was still making more power than I was using. If I would have had a mini-split ( heat pump)my current draw for the same cooling would have been hugely lower. On a bus, my plan is 400w portable solar set out in the sun at proper tilt/azimuth with the bus parked in the shade with Wave 2 running as needed from 2kwh storage. I plan to insulate the crap out of the bus. I will add more solar and or storage as needed. I say just start somewhere and adjust along the way. Make your best educated guess and then just go for it.

Wed Jan 15, 2025 7:38 am

Move to northern WI. We don’t need no stinking AC!

Sun Jan 19, 2025 4:48 pm

.

1500 watt tent airconditioner would work

https://www.amazon.com/DENBIG-Portable-Conditioner...3&th=1

This is a 2 amp draw at 120V, even looking at a very bad power factor of 0.5

https://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.html

"Compact and Portable: With dimensions of 20x10x10 inches and a single-hand handle, our outdoor air conditioner is tailor-made for outdoor activities like camping and fishing.

Versatile Power Options: Our AC unit can be powered by household outlets or portable power stations, offering flexibility for various locations, including tents, RVs, vans, trucks, trailers, and boats. (Ensure that the interface is compatible with your battery.)

Energy-Efficient and Quiet: Operating at a noise level about52dB(A)"

Tue May 20, 2025 9:06 pm

We’re about to find out if this can be done. I was not in the position to drop $1500 on the Ecoflow Wave 2 but now that the wave 3 is out, a refurb wave 2 is on eBay for $429 with a 30 day return policy. It doesn’t come with a battery and that kind of kills the efficiency because it will run thru my ac inverter while I’m not on shore power but, I’m willing to try it since I already have so much invested in batteries. I can buy the newer wave 3 battery if this all blows up and doesn’t work. Also if this does work I recommend just getting the Ecoflow full system and don’t hack it together like I did. They have it all as a kit now and it will work much better.

My solar panels are the thin flexible kind and are taped down to the roof with this gnarly strong RV tape. Been there for 2 years with no issues. I did forget to disconnect them over the winter and cooked my solar controller but that was just a slightly expensive mistake on my part. Again, if I was starting over I would like them to be mobile. The problem with them permanently attached to the roof is I can’t park in the shade to stay cool.

Anyway, here goes nothing. My hope is this isn’t as disappointing as the icybreeze cooler…

Tue May 20, 2025 9:54 pm

Hell yeah, good luck! I saw your post in the vanagon forum but didn't have anything to add.

How did you cook your solar controller? The basic models have pretty clear bold print: "Do not connect to panels until connected to battery." I can't imagine Victron hasn't solved that problem by now…

There isn't a ton of boondock camping anywhere near Chicago, are you going to stay in campgrounds with hookups? Battery life is a non-issue then…

Robbie

Tue May 20, 2025 10:34 pm

will give you brief moments of cooling and many moments of grief because the math does not work out. Like Robbie says, stay where there is AC power available at night. 400 watts of solar does not run a 580 watt unit without draining the battery. And after the sun gets lower in late afternoon when it is hot and humid outside, 580 watts at 12V is close to a 50 amp draw. That is why you hear generators running in RV parks at night where there is no shore power available.

Tue May 20, 2025 10:46 pm

The people with working electric AC in their buses are too busy enjoying themselves to post here. So what if the batteries drain? That’s their job, followed shortly by a recharge cycle.

It works better in northern areas with longer summer daylight hours for solar, and in the Midwest/northeast where campgrounds with shore power are plentiful. Removing humidity is a primary function of AC, and there is no metric unit for how a human body feels that relief.

There is no free lunch, but a little snack is better than fasting.
Robbie