ice box conversion to 12V cooler

[SteveK]

I have a built in ice box and would like to convert it to operate as a mini fridge to eliminate 'ice block' used for items that just need to be kept cool.
There are coolers that run off battery cig lighter which inspired the idea.
Thermoelectric 12V coolers are available to add on.
Anyone done this? Pros/Cons

 

[Comodave]

I suspect it will not cool enough to make it a fridge. If a $40 system would work then the traditional refers would be out of business. How does it transfer the heat out of the cooler since it is self contained? Am I missing something about how it moves the heat out of the cooler? And the unit must create some heat when it is running, where does that heat go if the unit is inside the cooler? I don’t want to rain on your parade but I am skeptical about a $40 unit. Although I admit that I am certainly no expert on refers.

 

[DavidM]

My experience with Peltier effect dehumidifiers tells me that they are horribly inefficient, which is what you don't want on a boat with limited DC capability even if it did cool your icebox satisfactorily, which I doubt.

But in my sailing days I had several boats with DC refrigeration added to their iceboxes. It is reasonably easy to install and they all work with efficient Danfoss DC inverter compressors. Alder Barbour, Nova Cool, Frigoboat and Engle are the names that come to mind.

These units use 50 to 100 amp hours daily.

David

 

[SteveK]

I suspect it will not cool enough to make it a fridge. If a $40 system would work then the traditional refers would be out of business. How does it transfer the heat out of the cooler since it is self contained? Am I missing something about how it moves the heat out of the cooler? And the unit must create some heat when it is running, where does that heat go if the unit is inside the cooler? I don’t want to rain on your parade but I am skeptical about a $40 unit. Although I admit that I am certainly no expert on refers.

Dave, think cooler, not fridge. I have a fridge. For lettuce and fruit, a cooler. An ice block works but takes space. I have portable cooler with one of those 12V devices on the side that chills beer cold. Does not freeze of course.

 

[SteveK]

My experience with Peltier effect dehumidifiers tells me that they are horribly inefficient, which is what you don't want on a boat with limited DC capability even if it did cool your icebox satisfactorily, which I doubt.

But in my sailing days I had several boats with DC refrigeration added to their iceboxes. It is reasonably easy to install and they all work with efficient Danfoss DC inverter compressors. Alder Barbour, Nova Cool, Frigoboat and Engle are the names that come to mind.

These units use 50 to 100 amp hours daily.

David

Thanks, I will research those add ons too. Again, not looking for another fridge, just a cooler.

 

[psneeld]

This is what I used....but it was a lot cheaper on sale at Defender a few years back. Easy install though.


https://www.westmarine.com/buy/dome...GR6nqFyLfpXzxsvPVREaAn13EALw_wcB&gclsrc=aw.ds

 

[SteveK]

This is what I used....but it was a lot cheaper on sale at Defender a few years back. Easy install though.


https://www.westmarine.com/buy/dome...GR6nqFyLfpXzxsvPVREaAn13EALw_wcB&gclsrc=aw.ds

excellent device for a boat built in fridge/freezer. But overkill for cooling I have in mind, 40-50*.
Had a small bar fridge with the device I linked but that was off 110V, worked great in garage for beverages. As it was 110 to 12v, gave me the idea here.
The Portable cooler does the job but takes up space, uses extra power stored in the sun.

 

[RT Firefly]

Greetings,
Mr. SV. It's been mentioned but power draw is noted as 6 amps. That's 144 amps/day (doesn't cycle). VERY power hungry.
We have one of those cigarette lighter coolers we had used on our small boat. Could only stay off shore power for 1 day due to limited house bank. Last year, changed our on board ice box to a Dometic AC/DC unit (draws 4 amps ONLY when compressor is running), added 100W solar panel and we're good for weeks off grid.

 

[DavidM]

Ok, I get that you are just cooling and not refrigerating down to 35-40 degrees. How big is the ice box you are wanting to cool. A smallish one would be about 4 cu ft, so call it 1'x1'x4' just for the following wild ass calculations.

A moderately insulated ice box probably has an R of 10 or so. Let's assume that the outside air temp is 75 and you want to cool the inside to 45, a differential of 30 degrees. That 1x1x4' space has an external area of 18 square feet. So the hourly heat load is 30*18/10 = 54 btu per hour.

A small Danfoss compressor refrigerator can handle 200 btu/hr. Danfoss compressor systems are about twice as efficient as Energy Star fridges and Peltier effect coolers are at least 3 times worse than Energy Star fridges, so a factor of 6 between the Peltier and Danfoss coolers. A Danfoss based system makes 200 btu/hr from 4 amps xv12V = watts per hour or about 4 btu/watt.

That Peltier effect module you referenced requires 65 watts. So it would make 4*65/6= 43 btu/hr, the six being the efficiency ratio between the Danfoss and the Peltier.

So the Peltier effect module is a little small for my theoretical 4 cu ft fridge. It might work if you are willing to spend $40 and cut a hole in your ice box. Also that module looks like it might be a little more efficient than the ones in the tiny dehumidifier that I am basing my numbers on. And taken together I could easily be off by half or double.

David

 

[SteveK]

DavidM, you got what I have in mind. Yes to 4 cube feet ice box. Just want to keep the summer heat off food stuff that does not require a Fridge between store and table, but will wilt in the heat on the counter.

Looking for a Danfoss add on, or a Dometic add on. If it was not for the power drain of the original idea, I would be done doing the install.
Looking for reasonable options to that.

I had a 110V bar fridge that used 60 watts that I ran off the inverter. It cycled so batteries lasted.
I have the built in box. Need to cool it

 

[PM]

Those little cigarette lighter run coolers will keep drinks drinkable cool for overnight, if they were cool when they went into the cooler. They will kill a car battery overnight. Plus there isn't much room in them.

pete

 

[syjos]

DavidM, you got what I have in mind. Yes to 4 cube feet ice box. Just want to keep the summer heat off food stuff that does not require a Fridge between store and table, but will wilt in the heat on the counter.

Looking for a Danfoss add on, or a Dometic add on. If it was not for the power drain of the original idea, I would be done doing the install.
Looking for reasonable options to that.

I had a 110V bar fridge that used 60 watts that I ran off the inverter. It cycled so batteries lasted.
I have the built in box. Need to cool it

Contact Dave at Seafreeze, Bellingham. He will recommend or build you a custom efficient compressor/condenser/evaporator unit. He is the marine refrigeration guru on Puget Sound.

I have several Seafreeze products and they are high quality dependable units. And Dave provides excellent pre and post purchase support. They are a small company.

 

[GoneFarrell]

+1 for sea freeze.

I keep some eggs, lettuce under fwd berth, below waterline.
Nice and cool, lasts long time.

 

[C lectric]

I played with one of those cooler chests , Koolatron, about 5-8 yrs ago.
It never made it to the boat. It sat in my garage of course in the summer but there was NO direct sun on it. I gave up. It could not cool the interior of the chest adequately. Like you I was simply trying to keep things cool, not cold.

I rigged it with an electronic thermostat , $9.00 ea, from China and those worked well. The temperature differential between run/stop could be adjusted so it should cycle.

Still have them but the cooler was totally inadequate. I never even got as far as trying to work out the power draw as it couldn't cut it.

Unfortunately I do not remember the specific model. I seem to remember it was about 30 L or just under 8 USG / 6.6 ImpG.

I finally gave up and bought a Danfoss BD35 compressor equipped freezer/cooler from Dometic. It works and in our case the set temp. can be adjusted to use as a fridge/cooler, not a freezer.

I like the idea of the Peltier effect units but they are not practical, IMO, aboard a boat for longer term use unless it is day use only or when the boat engine is running the bulk of the time.


JMO.

 

[SteveK]

This is what I used....but it was a lot cheaper on sale at Defender a few years back. Easy install though.


https://www.westmarine.com/buy/dome...GR6nqFyLfpXzxsvPVREaAn13EALw_wcB&gclsrc=aw.ds

So far I have been comparing to this one. But not yet looking for a 2nd fridge. Also noted this would serve twice the capacity of the cooler I have.

Will also look at a passive cooling near a hull location below water line.
Pretty much ruled out the original thought.

Thanks all, pretty much sums it up.

 

[BruceK]

If you use something like the westmarine unit you won`t be using anything like it`s cooling capacity, power draw should be commensurately lower than quoted.

 

[FF]

The simple test is to put a hunk of ice in and close the box for a day or so.

Then weigh the ice and return it to the box .

A 24 hour melt of under 5lbs means the box will work as a fridge on most house batt setups.

This will require 50-100AH of 12v DC per day to be made up somehow.

 

[SteveK]

last summer a block of ice lasted 2 days without scientific measurements. stuff remained cool for 2 days.
chest style sitting over the engine, so I think it is well insulated.