Battery Powered Peltier (Electrothermal) Cooler?

Yes, you just hook it up to your battery. Some of them plug right in to a car cigarette lighter socket.

i dont want to plug it into a car though, i need it to be completely portable, but icant have the battery be 20 lbs like a car battery

There cannot be a light weight portable source delivering continuously 6A at 12V. No miracles.

then how does this exist..?

http://www.youtube.com/watch?v=9mo-Vcvo3II

Okay, just buy one.

Peltier devices have a very low performance factor. There are a number of these small units made for vaccines etc.

They use vacuum superinsulation (10-50 times less heat transfer than foam) and a very small cascaded set of peltier devices to offset inwards heat leakage.

They also often have a phase change solid to assist in temperature control. (solid CO2 or other higher temp material) They are costly, but when the vaccines get hot, they can lose efficacy.

When used

Such device only uses Power (W):5.9 Wats , about 13 times less than yours , so the battery could be 13 times smaller.

Expensive but works flawlessly. http://aspensystems.com/products/personal-cooling/driver-cooler/

Peltier blocks are abysmally inefficient. Also, their temperature differential is quite limited. If you try to squeeze more out of them, efficiency drops further. better insulation is worth its weight in gold. So is better design, that reduces heat produced to be removed. After these generalities, some more concrete comments.

I have yet to meet a proiect, where many Watts have to be removed on a continual basis with Peltier. What happens, when the battery run dry? The equipment melts down?

There are well working stacked Peltier coolers keeping the optical chip at 0deg.C in an astronomical instrument. It is removing a few 10 milliwatt heat from the chip, for a constant temperature, constant picture quality. Its total power consumption is 1 - a few Watts, depending on ambient temperature. You can buy it from amateur astronomy magazines. I prefer buying to reinventing the wheel.

Then there is more ways to skin a cat. A gas in compressed liquid form released in a thin capillary tube turns into gas at constant temperature. CO2, propane, various freons etc. provide you with diverse temperatures. This one can handle significant powers. I think, I did read about it on a NASA tech transfer site.

As far as energy densities and prices concerns, I rather lug around a few bottles of commercial compressed liquid, than an auto battery.

You can buy one at any truck stop with a truckers' supplies store for less than $100. They will cool the interior 40 degrees below ambient. Reverse the leads and they will heat your lunch. It was my experience back when I drove a truck, that if I made a little ductwork to blow output air from the air conditioner through the coolmate air intake, I could keep ice cream hard for several days.

Those truckstop coolers will flatten a car battery in 3-4 hours.

He needs a low wattage peltier cascade, which is 2 in series, inside a super-insulated box, or the battery weight kills it. They can also run solar, these super-insulated boxes.

I speak of the multi-layer mylar reflective super insulation in a vacuum with cabo-sil separator granules

I should mention this is NOT to cool a CPU, its cooling water that is heated to around 100F to about 40-50F.

does that make it easier?

At what flow ? Or if in steday system , how much water and in how much time you need to drop the temperature?

My comments are to a generic cooler, to offset inwards heat leakage to a superinsulated box holding biologicals of some sort (insulin in this case). I made no mention of cooling a CPU.

vaccine cooler

It is a common problem for which solutions have evolved for maintaining various biologicals for a time period in third world areas. the use is for insulin or vaccines.

The more they cost, the longer they last/less they weight.

some are battery, some solar and some run on burning wicks or propane

flow is around 2 gallons/min i need to drop the temp down in about 15-20 min, the demands for my system are much less than that for comp cooling, im making a system to cool myself off :P a human cooler.

also i cant find any equations for change in temp with resistance time V and A. any out there?

PS i can easily increase the flow rate if i need to,i just wanted to make sure the coolant absorbed the heat

With 77 W , it only will "cool" you when sleeping.

Ahh! That explains it all. Good luck.

Pour water over your feverish head. It is called evaporative cooler, about 5000% better than peltier. Calculate the efficiency, and don't call us in the morning. Better yet is vodka. Alcohol cools better and faster. I am not quite sure, how to do it with dry ice. I actually produced frostbite on my finger with liquid freon, accidentally spraying on it. That is a thought to contemplate.

I bought a Swedish unit a few years ago to establish a "cool box" in the boat.

Worked a treat, but the blurb which came with it said that it's only good for ambient minus 22degC.

Our summertime median ambient is circa 29 C.

It was only to extend the life of produce a little rather than be a refrigerator.

I'm going to build one into the kitchen cabinetry in the house, for exactly the same reasons.

Example: one doesn't have to buy crap 'spreadable' butter. Use the real thing, in the pat, and just cool enough to make it not spoil for the week that it takes to use it. 12deg is fine.

There's lots of food that doesn't need to be at -4 C. 6-12 is just fine.

If you want really "cold" it is possible to "cascade" the effect of Peltier units to achieve this, but it's more cost, and current, effective to use single a compressor unit. Using the Peltier units the cabinet will need air circulation fans ( tiny computer fans) as well. Not a large draw, but has to be factored in.

To refrigerate a 120L cabinet effectively will average about 1.75 - 2.00 amps/hr, assuming that it's a decently insulated cabinet.

Just a few thoughts,

Stu.

I doubt that Peltier coolers are really suitable at all for this purpose; you'll need too many (or too large) modules/batteries.

It has been my experience that these devices are current hungry. Portable, well that depends on what your definition is. I have had the best results by a water cooling system on the hot side.