gadgeteer123

so i got a 177watt Qmax peltier, 15.5volts max, i am putting 13.4 volts at 25 amps into it. i was trying to cool it with a 145watt rated heatsink, with higher rpm fan on it, and it worked for 10 seconds then the cold side started to get warm, i don't have any money to buy watercooling or get a monster sized heatsink, plus i plan on using it to cool drinks anyway's so i would like to know how i am suppose to cool the hot side well enough to make it work effectivley? i have blower fans and i have power supplies to overvolt fans and everything i dont mind if its a ghetto setup or not, but i would like it to not take up any more room than a cubic foot. so any ideas??

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DuckieHo

Are sure your putting 13.4V@25A? That's 335w..... you'll need watercooling or a very large heatsink to handle that (which you can't afford).


Stick your current heatsink under running cold water....

Undervolt the TEC more..

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gadgeteer123

well the tec is rated at qmax177w at 15.5volts at 26amps max, it was a cheap peltier, and i dont have anything lower than 13.4 volts that has enough amp output, i have a 1 amp that is variable but i know that wont be enough, i do have a 5 volts output at 20 amps from a pc power supply would that work??

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zipdogso

gadgeteer123...can you supply me with a link to the TEC you bought off EBAY because things really don't add up.

A 177ww TEC will not generally draw a max of 26amps it is usually about 20amps.
I'll hanker you may be supplying 25amps but it wont draw it if it doesn't need it and you wont know without having an ammeter attached.

At anything greater than about 50% input power will require you to watercool the hotside and that's the only way it will work. The heat coming of the hotside is roughly double the cooling power so if you were running this at 12v for a cooling power somewhere in the region of 130-140w you would have up to 280w in heat coming off the hotside.

EDIT - My rapid maths was not very accurate you will need to power it 40% or less to cool it with a heatsink/fan combo.

The problem with doing this is of course it will only give in the region of 70w cooling quite possibly less and the usefullness of this TEC is fast dissappearing when it wasn't great in the first place. also it will hurt your Dt badly which means unless you do keep the hotside nice and cool it won't actually chill much. The bonus will be good efficiency but I don't really think this will make any great impact on your electricity bill.

Your PC supply wont work unless you are prepared never to use it in a PC again and are prepared to cut it up a bit and do a bit of soldering on it.


JEEZ....I am sorry mate I keep on urinating on your ideas....I don't mean to mate, honest it 's just that this is the bare facts with TEC...it really isn't the easy pop-in device too many people think it is.

flak-spammer

Hey...what heatsink are you trying to use? Make and model if you could tell us we may be able to help.

zipdogso

He is not here so I'll tell you it is a 145w rated heatsink it is the one he already has and he doesn't have any money to buy another, he has already realized it is not big enough unless he undervolts by a heap - he has already felt it get a bit warm.

flak-spammer

Yeah my curiosity was as to who it was made by. If he had a PC PSU he could probably run it on a 5v (it wouldn't work that well but better than 12v I imagine).

gadgeteer123

well i have tried a pc power supply at 5v it does get nice and cold now, but its not good enough, then for testing reason, i put it in cold water and the cold side froze water. would one of those cheap 80 dollar watercooling kits work?

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zipdogso

LOL....yes it gets nice and cold at 5v BUT you have very little Dt, putting it in cold water achieved nothing really. In the cold water the hotside was within a few degreees of the cold side so with a low DT the coldside was able to go below freezing. once you put this in to a PC equation with just a 5v power the hotside will be very much warmer and the low Dt means the coldside will only be a few degrees cooler - certainly no where near freezing.
This is why I keep trying to tell you it wont work - it is all down to you not understanding how TEC's work.

If you can be bothered to read it, I will try and explain......

Dt is the difference in temp between the hotside and the coldside. To get the coldside temp i.e. how low a temp the coldside will reach, you take the Dt from the hotside temp so if your Dt is 20 and your hotside is 32 the coldside temp will be 12.
Dt is very important in TEC. Initially it has a max of about 68-70ºC this is at max power. As you decrease the power the Dt initially drops very fast then slows down as you continue to decrease the power. It is not linear i.e. if you decrease power by a third the Dt will drop by more than a third.
At 5v roughly 30% power you have a small Dt, It is difficult to determine the Dt because it is affected by a number of factors not just input power, the only way to tell for sure is to run it.
When you put the TEC in cold water the large body of cold water kept the hotside cool so when you subtracted the Dt the coldside was below freezing and froze the water.
Once you put the TEC into a PC equation at only 5v power the hotside will almost certainly be a higher temp if you think about it the hotside will be at least equal to your ambient temp and quite easily 10 degrees higher than it, once you subtract the Dt the coldside will be no where near cold, I guarantee it wont be freezing....you see the problem ?
If you think about it the coolant in your loop will not be anywhere near as cold as that cold tap water you put the TEC in....will it ? honestly....
Also at 5v your 177w will only have a cooling power of about 50w.

gadgeteer123

well idn what to do now, i guess i'm gonna have to buy a bigger heatsink like a thors hammer or something like that for this, do you guys have any suggestions to the cheapest heatsink i can get that will be able to dissipate the heat output if i put 13.4 volts into this??

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