12 volt cooler or refrigerator

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jimmy alonso
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Re: 12 volt cooler or refrigerator

Post by jimmy alonso » Sat Jan 20, 2018 12:31 pm

Used my Engel for 90 days on Solar Power and one 102AH AGM battery because of hurricanes Irma and Maria. After 12 hours overnight about 35 amp hours were used. This is including running a 12 volt fan (.5 amps) all night and a LED lamp on an inverter (1 amp) for 4 hours at least. Plus cellphones.
The Engel would be packed full and I set it on #2.

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Re: 12 volt cooler or refrigerator

Post by K9Kampers » Sat Jan 20, 2018 7:07 pm

Back when part of the conversation was about needing heat exchangers and where to put them on a Mac...

Here's something for your mind to noodle on... rudders, or centerboard! Make one of the rudders, or the cb to also function as a heat exchanger for fridges or whatever else. I know it's a wacky idea (that might actually work) and is not without several challenges to overcome, but...

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kadet
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Re: 12 volt cooler or refrigerator

Post by kadet » Sat Jan 20, 2018 8:05 pm

K9Kampers wrote:Back when part of the conversation was about needing heat exchangers and where to put them on a Mac...

Here's something for your mind to noodle on... rudders, or centerboard! Make one of the rudders, or the cb to also function as a heat exchanger for fridges or whatever else. I know it's a wacky idea (that might actually work) and is not without several challenges to overcome, but...
Embedding a heat exchanger in a rudder or centre board would require a far bit of fabrication then you would have to have a flexible connection for the refrigerant pipes. Not very practical or easy I would imagine.

The easiest way is with a keel cooler and they exist, it is a bronze thru hull that acts as the heat exchanger most efficiently and bolts straight onto the compressor :)
Image

Not cheap mind, but what is for a boat 8)

https://www.outbackmarine.com.au/ground ... thout-zinc

PS I have nothing do with outback marine they just came up in my google search for pics and info :)

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sailboatmike
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Re: 12 volt cooler or refrigerator

Post by sailboatmike » Sat Jan 20, 2018 8:52 pm

As far as I can see every other option to a proper compressor drive fridge is going to end up costing more and / or being less efficient.

You cant make a silk purse from a sows ear and thats exactly what you are trying to do with thermoelectric, Im sure if they could make them better they would of, but while they have made some genuine improvements in the technology it just makes them slightly less efficient, as I say great for cars and trucks when power isnt a real issue, becomes problematic when you have to make your own power.

Of course if you have the time and patience to mess around Im sure you will be able to come up with something, plenty of YouTube videos of "Redneck" cooling units, but I just feel in the long run it will cost you more and still be less efficient never mind the time you have invested in it

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Sumner
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Re: 12 volt cooler or refrigerator

Post by Sumner » Sat Jan 20, 2018 9:07 pm

My belief is for the majority of boaters trying to mess with water cooling is just not worth the expense and trouble of more plumbing, a pump and another thru-hull fitting that will need to be kept free. I wondered about going that route with the Endeavour that is in Florida and it seems most popular in the tropics but our experience is that it isn't needed.

We have spent months and months on the boat using the fridge with an air cooled compressor. Been in Florida into July when the outside temps were low-mid 90's and the cabin temps were 85-87 in the day and just a few degrees less at night and the air cooled compressor has worked just fine. I wouldn't want to be on the boat if it was much warmer than this with the high humidity here.

A number of the boats in the yard have changed out their water cooled units since they didn't like them on the water that much and couldn't use them in the yard up on stands.

Put your time and money into a proven method of refrigeration unless you have time and money or both to spend on experimenting. Me, I just want a fridge that works efficiently,

Sumner

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Last edited by Sumner on Sat Jan 20, 2018 9:08 pm, edited 1 time in total.

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Re: 12 volt cooler or refrigerator

Post by K9Kampers » Sat Jan 20, 2018 9:08 pm

Image

Now that thing looks much more promising for a Mac than the bigger keel coolers that I was picturing. No need for the rudder cooler idea with that.

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Neo
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Re: 12 volt cooler or refrigerator

Post by Neo » Sat Jan 20, 2018 10:15 pm

Thanks guys some great feedback here.
sailboatmike wrote:As you can see its just a vicious loop that you cant win, the body of water just isnt big enough or cold enough
I just can't see how that volume of water would be heated by a little thermoelectric unit? Also the ballast water has large surface area of thermal conductivity (the whole hull) with the water below so I really doubt it would warm up at all.

Kadet ... What a great find ... The Keel Cooler is very interesting and has some real advantages so thanks for that.
K9Kampers Using the rudders, or centerboard is an awesome "brain storming" idea! .... This is the kinda crazy stuff I love to see :D

Summer I do everything on my Mac Just For Fun! and "letting my brain go crazy" is far more fun and far more challenging than buying any off the self solution. I've had MANY failed projects in the past but I am very proud of the ones that work well .... against all the odds :)

Thanks again guys. 8)

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Re: 12 volt cooler or refrigerator

Post by sailboatmike » Sun Jan 21, 2018 2:05 am

The temperature the hot side of a thermoelectric unit runs at is phonoimal, turn one on and put your hand near the hot side, the heat is amazing.

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Neo
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Re: 12 volt cooler or refrigerator

Post by Neo » Sun Jan 21, 2018 5:42 am

Hmmm ... Maybe I could fix the hot side to the underside of a glass jug (kettle) .... That way I could boil water (for my tea) and cool a beer can at the same time :D

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Re: 12 volt cooler or refrigerator

Post by Tomfoolery » Sun Jan 21, 2018 7:03 am

Just remember that the only heat the refrigeration will make is what it pumps out of the fridge or ice box, plus the extra due to efficiency losses of the refrigeration unit. Insulate the fridge/ice box well, and heat won't leak in very fast, so it won't have to be pumped back out. Unless you load it with warm stuff, of course (see BOAT's comments on prechilling beer in the ocean :wink: ).

I like my thermoelectric cooler, but I leave it running 24/7 on shore power, and mainly day sail. I don't care what the efficiency is, nor how much heat it generates (it's really not much, on the scale of the internal volume of the boat and how well it's vented). But for living on battery power, I don't see how you can get any better than some of the high-end compressor driven coolers. Put a thermal blanket over it to help insulate it (while keeping the vents clear). Or stick it into an insulated box, also while keeping the vents clear to the outside (boat interior).

And the warmer you set it, the less it will run - the driver of heat transfer is temperature difference, so the warmer you keep it, the slower heat leaks into the interior, and the less it will run. Same reason you use a set-back thermostat in your house, assuming you use one.

I used to put a couple of bags of ice in the ice box of my last boat at the start of a trip, to take some of the load off the refrigeration system. Doesn't matter how long the ice lasted (usually a few days at least), as any heat absorbed by the ice as it melted was just that much less that the cold plate system had to pump out. If and when it was practical to reload the ice, I would. Draining was automatic through a thru-hull. I don't know if that would be practical (or even necessary, really) with a small powered cooler and solar panels.

Just some more random thoughts. :wink:

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Sumner
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Re: 12 volt cooler or refrigerator

Post by Sumner » Sun Jan 21, 2018 8:41 am

Neo wrote:...Summer I do everything on my Mac Just For Fun! and "letting my brain go crazy" is far more fun and far more challenging than buying any off the self solution. I've had MANY failed projects in the past but I am very proud of the ones that work well .... against all the odds :)

Thanks again guys. 8)
My last post was not really directed at you but thoughts in general aimed more at someone contemplating adding refrigeration :wink: . I have lots of projects also that either didn't do the job or did, but aren't needed and are laying around the house :)

A big one for the boat was trying to use a trolling motor for more than getting to and from a dock. The verdict is still out on that one, but the solar I added to try it sure has been a big plus and glad that it is there,

Sumner

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Sumner
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Re: 12 volt cooler or refrigerator

Post by Sumner » Sun Jan 21, 2018 8:57 am

Tomfoolery wrote:....And the warmer you set it, the less it will run - the driver of heat transfer is temperature difference, so the warmer you keep it, the slower heat leaks into the interior, and the less it will run. Same reason you use a set-back thermostat in your house, assuming you use one.....
....and the opposite of that can work also if you have excess solar that is going to waste. If the batteries are topped off turn the fridge colder during the day and then at night back up as you suggested. It will take time to climb back up to the higher temperature and during that time you won't be using electricity. I've done this over the years and now they have a product that does just that automatically and works with a lot of the danfoss compressor units......

https://www.westmarine.com/buy/isotherm ... oC3Zjw_wcB

A good short youtube ...

https://www.youtube.com/watch?v=F2hAWqFVkUI

This product won't work on our portables, but you manually can do the same thing by watching your volt meter and solar charge controller to see when the charger goes out of bulk charging or do it when you are running the outboard if it is capable of higher amperage output.

I considered getting one for the fridge on the Endeavour but we run it all the time anyway just over 32 to keep the freezer compartment as cold as possible, which still isn't that much below freezing (high 20's),

Sumner

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Re: 12 volt cooler or refrigerator

Post by Tomfoolery » Sun Jan 21, 2018 10:13 am

An excellent suggest (as usual). I had forgotten that I had actually done that on one long trip when my keel boat was plugged into shore power, and turned it warmer when under way. No solar. Kept a couple of bags of ice in there when possible.

I had no idea such energy conservation systems were available for boat fridge systems. I'll keep that in mind if I get another large boat (a trawler or tug, if anything), which I'd like to do at some point. :wink:

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Re: 12 volt cooler or refrigerator

Post by RussMT » Sun Jan 21, 2018 12:38 pm

Sumner wrote: and now they have a product that does just that automatically and works with a lot of the danfoss compressor units......

https://www.westmarine.com/buy/isotherm ... oC3Zjw_wcB

A good short youtube ...

https://www.youtube.com/watch?v=F2hAWqFVkUI
That is a cool device. Should be standard on fridges.

BTW...we also bring a bag of ice and stick it in the fridge. It helps cool it down so the compressor doesn't have to work so hard and I believe acts as a "plate" to provide cold mass to keep things cold. Generally, the bag of ice is still frozen after 2 days.


--Russ

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Neo
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Re: 12 volt cooler or refrigerator

Post by Neo » Mon Jan 22, 2018 5:30 am

RussMT wrote:Generally, the bag of ice is still frozen after 2 days.
Hmmm .... you see it's things like this that makes me wonder why I'm bothering with a fridge :?
And the best way to conserve energy is to "keep the lid closed!".... or get-in-and-out as fast as you can! :D :P

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