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WhirledTraveller
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Joined: January 09, 2008
Posts: 1399
Location: Cambridge, MA
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 Posted: Mon Aug 29, 2016 3:47 am Post subject: Re: portable ac unit |
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| Wildthings wrote: |
| WhirledTraveller wrote: |
No 480 running watts is about right for a 5000 BTU air conditioner. Expect the startup load to be significantly more.
Consider that you can buy a 15,000 BTU window unit that runs off a regular outlet. |
480 Watts is 40 amps so I doubt that a stock charging system or battery is going to sustain the load for long. |
I think we are getting the two units mixed up. The thread started with a link to the "zero breeze" which is a "portable" AC unit that runs off DC with an optional battery pack, has a maximum 1100 BTU, and draws 120-150 watts.
I responded with a link to a different unit, the "Noria" which is a compact 5000 BTU unit intended for residential use and draws 480 watts off of 110V outlet, a little more than 4 amps. This is normal for a high efficiency modern AC unit. Obviously if you ran if from in inverter then you would be pulling more than 40 amps at 12 volts DC.
My point was that whether you are running a small unit at a lower power draw, or a larger unit at a larger power draw, the amount of cooling you are going to get from a certain amount of battery capacity is basically the same. You can't run either all night or all day and if the larger unit cycles on and off with a thermostat it will emulate the performance of a smaller unit running full tilt. You basically need generator or shore power to make air conditioning realistically feasible, in which case why not go for the unit that cools rapidly and mounts discretely and has a reasonable chance of actually making it to market.
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WhirledTraveller
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Joined: January 09, 2008
Posts: 1399
Location: Cambridge, MA
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| Posted: Mon Aug 29, 2016 4:12 am Post subject: Re: portable ac unit |
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| asiab3 wrote: |
| WhirledTraveller wrote: |
Expect the startup load to be significantly more.
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I'm not sure about that. The whole draw (pardon the pun) to rotary compressor for fridges/AC units is how they start with a small stroke and gradually increase the stroke until peak efficiency is achieved. This alleviates much of the start-up draw that typical compressors face. Engle/ARB fridges work this way too.
Robbie |
I was mentioning startup load for the Noria, which is a traditional AC unit designed for residential use and AFAIK uses a "standard" compressor with the associated startup loads. You can buy expensive air conditioners with low startup load, typically mini-splits, they use inverter technology to provide the "soft start" to a variable frequency 3 phase permanent magnet motor vs just attaching an standard alternating current motor to a compressor. Fun fact of the day is that they achieve high efficiency despite converting the household AC current to high voltage DC, then inverting back to 3 phase AC.
As for rotary compressors... there are many different designs. "Rotary" is just a generic term for how it achieves compression. Some are fancier than others and a basic rotary compressor is still fixed displacement and doesn't "ramp up". There exist variable displacement rotary compressors which is what you are referring to. There are also variable displacement piston compressors which are what you commonly find on modern automobiles. They achieve variable displacement by using a swash plate to alter the piston stroke.
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Abscate
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Joined: October 05, 2014
Posts: 22633
Location: NYC/Upstate/ROW
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| Posted: Mon Aug 29, 2016 9:23 am Post subject: Re: portable ac unit |
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If you are looking for AC (not 'breezes', and 'cool air' )which will work off either solar or batteries - you won't find it. Period.
It's simple thermodynamics.
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curtp07
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frankenwabbit
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Joined: January 04, 2007
Posts: 97
Location: california
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| Posted: Mon Aug 29, 2016 2:02 pm Post subject: Re: portable ac unit |
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I've made one of those when I took my bus from CA to TX during the summer. 45 minutes...tops. That's how long one of those lasted (the ones where you loaded ice into a cooler and had a fan blow).
I even had a setup with a water pump to a heat exchanger loaded with ice and water.....45 minutes...done...after that didn't really do squat.
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-frankenwabbit
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PopTopDreamer
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Joined: October 20, 2016
Posts: 107
Location: Canada
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| Posted: Sun Apr 02, 2017 5:05 pm Post subject: Re: portable ac unit |
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| I would buy the zero breeze if it worked and wasn't a fortune... |
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VW.parrothead
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Joined: January 16, 2016
Posts: 27
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| Posted: Sun Apr 02, 2017 5:25 pm Post subject: Re: portable ac unit |
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| frankenwabbit wrote: |
I've made one of those when I took my bus from CA to TX during the summer. 45 minutes...tops. That's how long one of those lasted (the ones where you loaded ice into a cooler and had a fan blow).
I even had a setup with a water pump to a heat exchanger loaded with ice and water.....45 minutes...done...after that didn't really do squat. |
Like this?
http://www.lifehack.org/articles/lifestyle/beat-the-heat-with-this-20-diy-air-conditioner.html
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mainstreetprod
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Joined: March 09, 2017
Posts: 313
Location: Tennessee
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| Posted: Sun Apr 02, 2017 6:14 pm Post subject: Re: portable ac unit |
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| I suspect this does not have enough capacity to cool anything during the day, with the sun beating down on your van. At night, it can probably make your camping experience a bit more pleasant. |
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kenfolk
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Joined: August 16, 2011
Posts: 34
Location: Arden, NC
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| Posted: Mon Jan 20, 2020 2:28 pm Post subject: Re: portable ac unit |
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Looks like these have been available for a while.
The zero breeze that is.
Anybody have any experience with one?
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon Jan 20, 2020 3:12 pm Post subject: Re: portable ac unit |
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120 - 150 watts is about 10 to 12 amps at 12V DC. Your battery won't last long at that rate. You'd be better off putting a trailer hitch on the bus, and a utility rack to mount a generator you can run going down the highway, and move away from the vehicle at night so you don't die of CO poisoning.
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