Peltier cell beer cooler

[Ledwardz]

Hey people,

so i am sick of drinking warm beer when camping.......

I plan to use 2 x 11.1 V (so probably nearer 12 V) 5500mah lipo batteries connected in parallel which if im right in thinking will give me near to 120W give or take. Am i also right in thinking if i am drawing 120 W it will last for one hour assuming it can give 5.5A consistantly for 1 hour?

The peltier cells are 12V, 25W. I plan on using 3. I am told because of the seebeck effect they cause a back voltage which i obviously dont want damaging my batteries. My first question is therefore, is it as easy as placing the correct diode in series with the battery and cells? If so, can anyone reccomend any diodes rated for the power required?

My second question is regarding the pelteir cell itself. I am aware they are rated in temperature difference. I want to connect copper pipe to the peltier cell in the hope that when the peltier cell cools down the copper pipe wrapped around the beer will too. Does anyone know what will stick copper pipe to the peltier cell so that it conducts the cold temperature well. I have never seen this done be4 - is there some reason y?
If i want to cool the copper pipe will i have to place a bigger heat sink too? will they damage if they get wet off the condensation - are they water proof? Any adivce on them is much appreciated.

if anyone has any thoughts on any of it, it would be good to hear from you,

Cheers for reading,

Lee.

 

[(*steve*)]

A typical method of using them is to get an insulated container (an esky) and make a hole in it. The peltier device sits in the hole with heatsinks connected to both sides. You can connect a small fan to either or both sides too.

When you power it up, one side gets hot, the other cold. If the inside gets cold you put beer in it. If it gets hot you put coffee in it.

The seebeck effect will not damage your batteries.

2 x 11.1V batteries rated with a capacity of 5500mAh will give you a capacity of 11 * 11.1 Wh, that's around 120Wh. So assuming you can discharge them at the rate required, you can get 120W out of them for 1 hour.

Using peltier effect devices to cool things is not very efficient. For a start, you're pumping in power (120W in this case) which you have to get rid of before anything will happen.. Then you need to get rid of the heat pumped from one side to the other. (As wikipedia says, the major drawbacks are high cost and low efficiency)

If you connect the peltier device to a thick aluminium late on the inside of your esky, you can stand the cans on this and it will keep them cold. The insulated container is a must, and I'd advise cooling them using a regular fridge first.

Have you considered ice? If you only need to keep things cool for a few days, a couple of bags of ice in a good esky should do the trick.

 

[Harald Kapp]

You're mixing up terms and units.
mAh (or Ah) is the capacity of a battery. W is power. Both are somewhat unrelated.
While P=I*U, the curent I does not depend on the capacity. You can draw e.g. 1A current from a 1Ah battery or from a 10Ah battery. Power in both cases is the same (provided the battery voltage is the same), but the 10Ah battery will last 10 times longer than the 1AH battery.

So: 2*5.5Ah batteries in parallel will give 11Ah (capacity aka stored energy). When you use 3 cells at 25W/cell you have 75W which is equivalent to I=75W/11V=6.8A. 11Ah/6.8A=1.6h. Your batteries will last approx. 1.5 hours.

You'd need a diode only if the voltage generated by the peltier cells is higher than the voltage from the batteries which is most liekly not the case. A diode will only reduce the voltage available to the cells and the energy lost in the diodes is lost for cooling. If you insist on using a diode, use one rated for 10A or more, preferably a Schottky diode to minimize losses in the diode.

Cooling a copper pipe vial peltiers is probably not done because pipes are round and peltiers are flat ( at least typically - I don't know other forms). This makes for a bad contact and veeeeery inefficient transfer of heat from the pipe to the cell.
I recommend a different approach: Insert a metal tank into a standard ice chest. cut a hole in the insulatin of the chest such that you can attach the peltier elements to a flat side of the tank (e.g. using thermally conductive glue). Attach a heat sink to the other side (outside) of the peltier elements to remove the heat. Fill the tank with cool water, put the bottles or cans into the water.
The water will very effectively transfer thermal energy from the bottles to the tank, from there it is "pumped" to the heat sink by the peltier elements. A further advantage is that he water will help the beer stay cool once the batteries are sucked empty. You can even add ice to the tank at the beginning to extend battery lifetime.

Note that you should put a protection circuit in place to avoid discharging the batteries below the recommended limit. Otherwise you risk damage to the batteries or even worse.

 

[Harald Kapp]

 

[OLIVE2222]

Cooling the beer is a VERY important matter.
We must so have the intellectual honesty to admit that electronic based solutions can not be the best ones !

http://www.wikihow.com/Cool-Beers-Without-a-Fridge

Olivier

 

[Ledwardz]

There may b better ways of doing it, i just want something to do. I am not bothered about the price of it either. I dislike warm beer and all the other methods of cooling beer seem like hard work - fetching water and socks and such.....

I was thinking along the lines of cooling 1 beer can at a time with the aim of having a cold beer after 10 minutes if possible then turning the system off. Incorporating a sprinkle water syste, a high power fan (im hoping this will vibrate the can just enough so that the liquid inside it moves around to help with the cooling) and 3 (or even 4 if the batteries can supply it) peltiers with copper strips wrapped tighlty around the can (as appose to pipe) (I had also considered using more peltiers and switching them on and off at different times.

see the picture - i know its pretty crappy and crude but something along those lines.

Thanks for mentioning the discharge of the batteries and providing the link, this wasnt something i even thought about. Thanks also for clearing up that the back voltage will not damage the batteries.

Regarding the esky / cool box idea, i imagine the peltier cells will hardly cool down a large volume of water at all and they would have to be left on constantly.

cheers for replies.

Lee.

 

[Harald Kapp]

Regarding the esky / cool box idea, i imagine the peltier cells will hardly cool down a large volume of water at all and they would have to be left on constantly.

They may not cool down the water, but they help keeping the water cool if you start with cool water (and some ice).

 

[donkey]

ok so having experimented with peltier I have found a few things out. now first is the voltage, while they are extremely current hungry at their peak (mine were 12volters) I found having the voltage also lowered the amps drain. off course it took longer to cool things but I still iced a few drops of water in under a minute.
a good heatsink is essential for this to work
I like using water http://www.ebay.com.au/itm/80x40x12mm-Aluminum-Water-Cooling-Block-for-CPU-Heatsink-Cooler-Peltier-Plate-/231176448411?pt=US_Water_Cooling&hash=item35d330a99b
problem is you then have to add a pump to the mix, a radiator etc.
lastly is the way the peltier works as far as my poorly educated brain figures is what ever the hot side is the cold side is "x" amount cooler. so unfortunately if you don't get the heat of the peltier the cold side will eventually go above room temp.
one day when I have 5 minutes during daylight I will build my Fridge/air con model and post pics. I know for a fact I will get some ideas on improving the design but to start I am just hoping to stop a really expensive summer time bill lol.
if you get yours going I would thoroughly enjoy seeing your progress

 

[donkey]

Ledwardz any update?

 

[Ledwardz]

Thanks very much donkey. These are something i had never considered and should reduce the size drastcally providing they work effectively. If you have used the peltier cells, what do you think about switching them on and off at different times? how long does it take to warm up to room temperature again? how long will it stay cold? how long does power have to be applied in order for it to be at its coldest. what temperatures am i likely to expect from them?

Here is a list of some of the things ive scouted on the tinternet. Haven't checked the nitty gritty details yet and i require a protection circuit for the batteries that i can get my hands on in the UK which i am currently struggling to do so.

Peltier coolers (25W) x 4
http://www.amazon.co.uk/DEOK-TEC1-1...F8&qid=1408504306&sr=8-1&keywords=25W+peltier

Peltier water cooled heatsink x 4
http://www.ebay.co.uk/itm/Water-Coo...ponents_Fans_Heatsinks_SR&hash=item43bf15c63a

12V water pump x 2 (not sure if powerful enough)
http://www.ebay.co.uk/itm/Ultra-qui...den_PondsWaterFeatures_UK&hash=item2591fc644a

water radiator heat exchange x 1 (i have spare fans)
http://www.ebay.co.uk/itm/Aluminum-...prg=20140107092241&rk=2&rkt=4&sd=121357684432

9.5mm pipe (need to double check all inlets are the same first)
http://www.ebay.co.uk/itm/PVC-Tube-...ondsWaterFeatures_UK&var=&hash=item3a8231dec0

Batteries
http://www.ebay.co.uk/itm/2x-11-1V-...sGames_RadioControlled_JN&hash=item35d4b4917d

copper strips
http://www.ebay.co.uk/itm/Venture-T...fts_Glass_Art_Supplies_CV&hash=item3f3a2d0776

cheers again,

Lee.

 

[donkey]

LAUGHING SO HARD RIGHT NOW. I HAVE NEARLY ALL OF THAT STUFF FOR MY AIR CON. AM MAKING A SWAMP COOLED/AIR CON
cos I am lazy I am not uncapping the above btw lol.
anyway the peltier itself is a tile. it takes a few minutes to get back to room temp BUT if you put something on it like a beer and the beer is, lets say, 4 degrees celcius, then think about how long it takes to warm up to room temp.
PWM the Peltier is a good idea, having a "turbo mode" button is also good. the question becomes though how do you sense the temp? you don't want your drink becoming iced and you don't want to rely on time alone. if you get really bored you can always give the peltier a running start by filling a cooler with ice packs so the Peltier works less.

 

[Maya]

"So: 2*5.5Ah batteries in parallel will give 11Ah (capacity aka stored energy). When you use 3 cells at 25W/cell you have 75W which is equivalent to I=75W/11V=6.8A. 11Ah/6.8A=1.6h. Your batteries will last approx. 1.5 hours."

Can someone explain why you used 11V? Shouldnt it have been 12V peltier? Im trying to understand basic calculations ahaha.

 

[donkey]

Maya a lot of people are using Lipo battery packs, these don't come in the 12volt variety.... oh and this thread is nearly a year old

 

[Maya]

oh ok. thanks!