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### How Do I Use Battery Power to Electrically Cool an Ice Pack Gel?

05/12/2012 5:35 PM

Hello all,

I just had a quick question. I am trying to create a prototype for a new invention that involves electrically cooling an ice pack or a substance similar to that affect, utilizing battery power. First, is this possible? I am in no way technically saavy in this regard and all my searches on the internet were not helpful. I wanted to use 4 AA batteries to create a circuit, and contained gel (like that of an ice pack or a mixture of water and rubbing alcohol) and create a cooling effect, ultimately strong enough to be equivalent to that of an ice pack. Please, if anyone has any idea or can lead me in the right direction I would greatly appreciate it.

-Johnny Bananas

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#1

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 5:42 PM

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#2

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 5:50 PM

After you discover the efficiency of the afore mentioned cooling plates, you'll need to think about how much energy is needed to remove heat from water or gel. Hint: 1 BTU will cool 1 pound of water 1°F. 4 AA batteries won't go very far.

BTU to kWh conversion calculator

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#3

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 6:17 PM

Solid state cooling is not going to be efficient enough to be practical in this application...What is your target heat load?

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#4

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 6:18 PM

You really should know more about thermodynamics and enthalpy to see if your idea is even possible. There is a finite number of Joules of energy in one AA battery. You need to know also how much mass you will be trying to cool to a certain temperature and from what initial temperature. If this mass will not be going through a change in phase state then the total energy required to be removed will be less. As Tcmtech highlighted, peltier devices will likely be your best bet.

The devilish details in this problem are just a few critical items:

• Thermally isolating what you wish to chill from the rest of the world but recognize that heat (power, joules per second) will still be coming in from the outside to heat what you want chilled.
• Identify all of the mass that will be chilled, not just the desired object.
• Removing the waste heat from your heat pump (peltier) without letting it to easily return back to the cooled item.
• Avoid any phase change in matter as possible. Condensing moisture out of the air and freezing water to ice will take a large amount of total energy.
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#5

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 8:44 PM

The amount of liquid/gel I will be using is around 2-3 cups (not sure of weight). The peltier cooling device (from what I can see) seems to be the kind of device I could use but I dont really understand how to utilize it in my prototype. What would be an optimal electrical source if batteries are not an option? And thank you for the help btw. Again, greatly appreciated.

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#10

### Re: How do I use battery power to electrically cool an ice pack gel?

05/13/2012 10:24 AM

Is this for transporting an unstable compound? What is the intended use?

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#6

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 10:19 PM

As previous posters have pointed out, using electricity to cool something is more complicated than using it to heat something. The electrical part is relatively easy, a properly sized power source, some wire, a switch and the thermoelectric cooler are all that are required from the electric side; however there are a lot of thermodynamic and mechanical engineering considerations that are more complex and involved. As you dig deeper you may find that the chemical solution to your problem is much simpler...

...and a whole lot cheaper.

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#7

### Re: How do I use battery power to electrically cool an ice pack gel?

05/12/2012 11:54 PM

This kind of device comes in versions that plug into a car cigarette lighter; i.e., 12 volts. You would need more energy than 4 AAs can provide, but you could consider 12v gel-cell batteries, which come in a range of sizes.

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#11

### Re: How do I use battery power to electrically cool an ice pack gel?

05/13/2012 9:09 PM

it's my understanding that thermo-electric coolers are only capable of lower the temperature only 40 degrees below ambient temperature.

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#12

### Re: How do I use battery power to electrically cool an ice pack gel?

05/13/2012 9:41 PM

In single stages, that or a similar limitation applies; it can be overcome with multiple stages (with poor efficiency, though).

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#8

### Re: How do I use battery power to electrically cool an ice pack gel?

05/13/2012 1:39 AM

JB -

You could find some really great ideas for your project if you do some research on the millions, if not billions, of \$\$\$ spent on this technology for several industries - Space (NASA), Fire and Rescue, Military, Medicine, and Sports and Recreation.

Big Players on the NASA Constellation extravehicular environmental systems (all new temperature regulating undergarments for space suits) included Dow, Gore, 3M, DuPont, Oceaneering, JPL, Boeing, and many more. Genius people with essentially unlimited funding. They have a system that works pretty good if you have a few million for the suit, and the vacuum of space to dump the heat into, and the weightless environment to help lug around the 215 pound device, plus the insulated suit.

What you want to do with your cooling pack is physically possible. Financially? Practically? Safely? Maybe not so much...

As others have said, a few of your problems are going to be the need for a huge power supply if you want this to work for more than a few seconds at best, how to get rid of the heat generated by the power supply as it creates the power you need for the cooling cycle, along with the heat your device sucks out of the gel/pack, and the overall mass/bulk of the system.

Please continue to work on it. Imagine the rush of figuring this out and being the guy who can say - "I just looked at it from different angles and kept going till I found something that worked."

Meanwhile, ice is pretty safe and cheap.

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#9

### Re: How Do I Use Battery Power to Electrically Cool an Ice Pack Gel?

05/13/2012 8:05 AM

It sounds as though a motor driving a Stirling Engine is what you want, Boss.

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#13

### Re: How Do I Use Battery Power to Electrically Cool an Ice Pack Gel?

05/13/2012 10:55 PM

Are you locked in to electrical cooling? If not, check out Vortex Tube cooling.

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