Thermoelectric refrigerator again...

[mikeschn]

After our dismal failure with our thermoelectric refrigerator a couple years ago, I resigned it to the basement to keep our beer cold. It works great for that.

However, rustic camping has me thinking about it again. What would it take to make it work? So I went downstairs and threw it on the inverter with a power supply. The power supply tells me it's drawing 6 amps, 24 hours a day.

That's 144 amps per day, or for a typical weekend, 288 amps. If I don't want to draw the batteries down more than halfway, I would need 5 huge deep cycle batteries for 2 days of refrigeration.

I think I'll leave the refrigerator downstairs...



Mike...

[Miriam C.]

ARe you bored today? All that math. Sounds like I need to keep the cooler still.

[madjack]

...you CAN lead a horse to water...occaisionally, he will even take a drink ......................................

[mikeschn]

Just had to double check before I place an order for an expensive gas absorption refrigerator.

Mike...

[brian_bp]

Thermoelectric coolers truly are power hogs; I have concluded that they are useful only for use in an operating vehicle. I have three.

If the desire is to run a refrigerator on battery power, then the other option should be considered: a compressor-type refrigerator, specifically designed for efficiency and running on 12VDC. They've been discussed here a number of times.

If the desire is just to get something cheaper than an absorption cycle unit, the compressor unit isn't much of a solution, but they do use much less energy than the thermoelectric type.

[brian_bp]

...The power supply tells me it's drawing 6 amps, 24 hours a day.

That's 144 amps per day, or for a typical weekend, 288 amps. If I don't want to draw the batteries down more than halfway, I would need 5 huge deep cycle batteries for 2 days of refrigeration...

Mike, I'm not trying to be picky, but people keep getting confused about this, partially because other people are not clear in their use of units of measurement...

6 amps for 24 hours is indeed 144, but it's amp-hours. An amount of charge is not the same as a rate of current flow, and mislabeling the first as just "amps" really throws some people in these discussions.

The weekend takes 288 amp-hours, which would be over 56 amp-hours for each of 5 batteries, which I agree would be about half of the capacity (and thus a reasonable level of discharge) of relatively big (group 27) batteries with a capacity of around 100 amp-hours each.

[mikeschn]

Yes, you're right... I should have said amp-hours!

Mike...

[raprap]

You could use watts. Six amps at 12 volts is 72 watts, about the same as a fair sized incadescent bulb, or a fluuorescent fixture with two 4 foot tubes, Figuting it runs all the time that is a good bit of power, more than my 60 watts of solar collectors put out at peak.

I too bought on of those Coleman peltier coolers and besides the power problem, they have a limited cooling capacity---no more than 40 DegF difference so if it;s 90 degrees outside, they only keep your beer at 50 DegF. And if it is dooler than 60 DegF, the beer can freeze. They're great for running vehicles, but if left for more than a few hours without the engine running you better be parked on a steep hill.

As for absorption units, not too long ago I saw a Norcold 1,7 cubic foot (55 quart) three way power frig in Whitney for $550. Don't know about shipping. Me I went back to ice, but I found a place that sells blocks--they last a lot longer than crushed.

Rap

[eamarquardt]

You have made the great discovery. DC power has real limitations. I didn't learn this via RV's but via sailing on boats. There are three factors:

1) How many amp-hours do you need.

2) How much battery capacity are you going to need (you really get only about half the rated capacity out of a battery).

3) How are you going to put the amp hours back into the batteries.

All three need to be addressed before relying on DC.

I bought a Norcold three way to install when I get off my duff and build the trailer. A/C and Gas work great. Even in the manual, however, they mention that DC power is really just to keep things going, not to really cool things down much. Use the AC and Gas to cool down.

I bought one of the little DC coolers at a garage sale for a couple of buck to see how effective thay are. I plan on dropping it off at the Goodwill the next time I drive by. I think they are next to useless.

Cheers,

Gus

[starleen2]

Used to have one of those fancy Coleman thermoelectric coolers that could go both ways – either cool or heat @12 volts. It never did what I wanted it to do. So I went to the outlet store and bought a cheapie 120v electric units with the built in freezer. Too small of a freezer to do any good. Needed to be plugged in ahead of time to begin cooling. Both are now history. I finally settled on a new Frigidaire 3.1 Cu. Ft. Compact Refrigerator / freezer unit. This works for me. Yes it is 120 v, but I can start freeze anything the moment I plug in. Thermoelectric coolers are probably good for some things, but didn’t work for us.

[brian_bp]

Whether the power consumed is measured in watts, or just the current is measured in amps, the problem with the thermoelectric cooler is not really just the power they take, but the fact that they seem to need it almost continuously. The compressor-type units might take about the same current (and thus the same power) when they're running, but that produces more cooling so they don't need to run nearly all of the time... unlike the thermoelectric unit which Mike tested.

That's where the amp-hours come in... amps times hours is the battery capacity consumed, and that's the critical factor in making through the weekend. Whether it's 6 amps (72 watts) all the time, or 12 amps only on half the time (144 watts peak, 72 watts average), it's the same total charge used.

[bgordon]

Hi all,

Yep, running a fridge or freezer when camping can be quite a challenge. Last week I came across this article. It was a VERY interesting read:

"A fridge that takes only 0.1 kWh a day?"

Link:

http://www.builditsolar.com/Projects/Conservation/chest_fridge.pdf

Hope it helps, even simply to stimulate someone to find a workable answer!

[jeep_bluetj]

My thoughts:

1. Propane gas absorbtion (Standard RV fridge)
2. Engel/ARB.

Neighbor has a mid-sized Engel that draws less than 3A. That's 72AH per day if it never shuts off. He says it runs at less than 50% duty most of the time, so that'd be 36AH. Way better than a peltier based cooler. And it gets well below freezing if you set it to freeze.

Only drawback is the massive $$$$$ of these things.

[Alphacarina]

Neighbor has a mid-sized Engel that draws less than 3A. That's 72AH per day if it never shuts off. He says it runs at less than 50% duty most of the time, so that'd be 36AH. Way better than a peltier based cooler. And it gets well below freezing if you set it to freeze.

Only drawback is the massive $$$$$ of these things.

Yes, but if you're going to use it a lot, it's probably still cheaper than going through 2 or 3 el-cheapo fridges and all the associated batteries/propane etc to keep them running for 4 or 5 years

I resigned myself to the absolute necessity of purchasing an Engel long ago

Don