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Old 16-10-2014, 08:07   #46
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Re: Air Conditioning on Batteries Only

One other option; for years I've been installing a small, 4.2Kbtu, 120v unit. A 3.5 amp unit at 120, it runs fine on an 800watt sine wave inverter and draws, with a 12v pump, about 35amps at 12v. Given a 60% duty cycle it will use about 150amps on an average evening dropping the temp in ONE CABIN to something easy to sleep in in even the most humid area.

The limitations are clear, one cabin and you'll need 150 a/h more or less, something a large house bank can supply.

We've put them in small cuddy fishing boats with outboards to run when they're underway and in large cruising sailboats to supplement an existing system without running the genset. There are lots of ways to do this if you only want to cool the sleeping cabin...
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Old 16-10-2014, 08:40   #47
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Re: Air Conditioning on Batteries Only

There are many chemistries for Li batteries. The ones based on iron (Fe) are very safe. LiFePo and some variations Fe, are perfect for house banks.
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Old 16-10-2014, 08:43   #48
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Re: Air Conditioning on Batteries Only

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Originally Posted by valhalla360 View Post
The only thing to ponder is a 60 degree radiator isn't as cold as a typical AC so how much cooling will it generate and is there a way to improve the thermal efficency enough that it is effective.
To a certain extent you could overcome this with a much larger surface area, say try a automobile condenser out of a junkyard and a 12V water pump for an almost no cost attempt, that with a 20" box fan, but you have to be somewhere cold water is accessible. If you could drop a large amount of air CFM to and have an air exchange every couple of minutes, then I bet it would work

Ground water temp is South Ga. is 68 deg. yr round, I've often contemplated using it as a source of cooling, have to have a huge radiator to completely cool your house, but what about just absorbing some of the heat, then pass the air onto the regular airconditioning? May cut the bill some?
I'll never do it, too lazy and want to move onto the boat anyway.
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Old 16-10-2014, 09:53   #49
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Re: Air Conditioning on Batteries Only

With a household system, you could simply stack a dozen old car radiators in front of a box fan fed into the cooling ducts and it should do the trick. If it doesn't add more radiators or a higher volume pump and eventually it will work (if it will be more efficent than a compressor based system is another question). But space becomes the bigger issue on a boat.

You would need a radiator with a higher surface area density (ie: more fins per square foot of radiator) to get the size down to something reasonable.

As you said, you need cold water to make it work but the Great Lakes and the Northeast, Baltic over in Europe should have cold water in abundance.
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Old 16-10-2014, 16:52   #50
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Air Conditioning on Batteries Only

On the house thing I was thinking if you could take incoming air at say 83 deg, knock 1 or 2 degrees off of that and then the AC take it and drop it another 1 or 2 degrees down to 79 or so.
I think that's achievable and should knock off a significant portion of the electric bill.
On a boat though. Surely if the water is like 50 degrees even a one pass condensor from an auto over a box fan would be significantly better than the fan alone? Not as good as a real vapor cycle cooling system of course, but until it's tried who knows?
Me water less than 80 degrees is too cold, not much cooling there
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Old 16-10-2014, 16:54   #51
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Re: Air Conditioning on Batteries Only

Isn't the breeze off of water that cold, plenty cool enough?
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