TEC's And Undervolting/Underamping/Lowering Wattage

[THE JEW (RaVeN)]

I was going to ask this in the new Swiftech TEC thread, but figured I might as well ask here.

Everybody seems to realize that the optimum way to run TEC's (in regards to efficiency) is to undervolt them (ie. 80% or less). Aside from hugely expensive, adjustable power supplies (the scientific ones with ranges from 12-24v are almost always at least $250), is there a way to get volts in the range of 17-19volts? I ask as I'm mainly interested in the 437watt TEC. I guess 9v would also be a consideration for people running the 226/320 watt.

For example, I have two Meanwell 12volt power supplies (adjustable +/-10% as per almost all of them). I'm wondering if there's anyway I can rig them to around 18v. I've looked at the wiring guide, but even at 10v a piece I'm still up at 20v. With ATX psu's, one can put 12v to the positive and 5v to the negative to get 7v. Anything like that possible with TECs? I've also been looking at puttting a couple of TEC's in series to drop their amp draw. Resistors are out as the amps needed are way too high and limiting that many amps would almost need its own cooling source.

Basically, I'm looking for ideas on how to increase efficiency on TEC's. Everbody talks about undervolting, but never really their methods on how to do so. Anybody have any examples of how they've done it? Or theories on how to?


ps. As an aside, which chart do people feel is closer to the actual performance of the 437watt TEC's? The first or second? Users of said TEC's input is greatly appreciated.

[n00b 0f l337]

People generally buy the meanwells, when those arent ajustable (and they normally get the s600-24), they might get a 600-18, or something like that.
I think the 2nd's the more accurate one as it matched much closer to my dominator 437.

[THE JEW (RaVeN)]

So, basically, you're saying that unless I buy an 18v psu I'm stuck at about 20v-21v.

Boo-urns :(


Any other ideas on the matter? Crazy or not, I'd be interested in hearing them.

[n00b 0f l337]

Huge rheostats to burn off the excess power? Not a good idea.

[THE JEW (RaVeN)]

Agreed. They'd need a massive amperage and you'd probably need to cooling some for of heatsink attached to the rheostats/resistors.

I was thinking along the lines of attaching a 6v high amp psu to the negative with the 24v going to the positive, but having the 2 psu's going would be a "bit" of a power hog.

[Orangeblast]

why would you want to undervolt a TEC? I thought that the more voltage you gave to a TEC (without blowing it) usually gives colder results on the cold side.

[m0da]

true, but the more voltage you give it, the less marginal benefit you receive. this is what they mean by being being less efficient at a higher voltage. Like this:
V Wdissipated
5 20
6 30
7 32
(not real specs)

basically from 5 to 6 volts, it will dissipate 10w more, but from 6-7 it will dissipate only 2w more. So, using less electricity, but still getting good enough performance is what they want to do.

bad explanation huh? \=

[n00b 0f l337]

More like, at a lower voltage it will move the heat more efficienctly.

[L33T]

That's a damn good explanation.

Are you an econ major by any chance?

^__^



true, but the more voltage you give it, the less marginal benefit you receive. this is what they mean by being being less efficient at a higher voltage. Like this:
V Wdissipated
5 20
6 30
7 32
(not real specs)

basically from 5 to 6 volts, it will dissipate 10w more, but from 6-7 it will dissipate only 2w more. So, using less electricity, but still getting good enough performance is what they want to do.

bad explanation huh? \=

[ColonelCain]

noob of 1337, do you know of anywhere that you can buy the Dominator 437?

[L33T]

noob of 1337, do you know of anywhere that you can buy the Dominator 437?

Anywhere other than what place?

[ColonelCain]

I didn't mention anywhere. I'd like to find out, thats all.

[n00b 0f l337]

Wintsch Labs went out of business. But i think they'll make them on demand.

[ColonelCain]

Hmmm... interesting. Just pulled this from their website:

Jan 15, 2007 - Arctic Web added to product line-up. The beast is back!
I'd loooovvveee to get this for my next rig, but this is the only problem. $50 Apogee block that'll might be able to get me to 4ghz on a Yorksfield QC, or $200 that'll definatley get me there.:(

[m0da]

Wintsch is having CNC/milling issues. they'll put you on some sort of "waiting list"...

@L33T: no, not an economics major... I'm just taking it now though. diminishing marginal utility ha.. think of it as eating the first slice of pizza vs. the 50th slice of pizza... that's what my prof says at least. i think it works:)

[L33T]

I didn't mention anywhere. I'd like to find out, thats all.

Ic. Well, you can get them from frozencpu.

http://www.frozencpu.com/exp-04.html#blank

[Duh]

Ic. Well, you can get them from frozencpu.

http://www.frozencpu.com/exp-04.html#blank
thats the tec only...:slap:

[THE JEW (RaVeN)]

Sorry to bump an old thread, but since it's mine and my next question is related..........

The Meanwell's have an adjustable pot on the back (ie. my 12v one adjusts from around 10-14v). Is there anyway one could do a simple mod to that pot? For example, change its resistance value so that you could decrease your volts down to about 8 or 9 volts?

Thanks.

[littleowl]

I am no electronic engineer but I don't see why not. If you changed out the pot to a different one you should be able to adjust better IMO.

[THE JEW (RaVeN)]

Yeah, I'm leaning that way too, but I just need a bit more confirmation before I bork my Meanwell. I ask because of this article:

http://www.tweaktown.com/articles/1200/4

quote:

"The peltier and the CPU fan are powered by a Meanwell 320 watt power supply designed for this type of work. By adjusting the voltage to the peltier to 9.5 volts and the CPU fan to 7 volts we can simulate an idle load."

He's building a cpu test bench and his Meanwell goes all the way down to 9.5 while mine makes 10.7 or so. Mine's roughtly within the specs that Meanwell publish (+/- 10% or 1.2 volts variability):

http://www.meanwell.com/search/S-320/default.htm

He says that he has two Meanwell's that go 9.5v or lower. Checking some of the older threads around here, it seems lots of people can get below 10v. I was just wondering if there was a cheap and simple way (ie. putting in a different pot) to make all the Meanwell's do lower than 10.5 v.

[littleowl]

hum I will have to hook mine up and see how low it goes! mine is a 320w 12v meanwell. I have not used it for several months though! :( (no time to play)

I will have to read them articles, looks very interesting!!

[pH(x)]

You could just try buying a Peltier with a higher VMax.

http://www.ferrotec.com/products/thermal/modules/

[THE JEW (RaVeN)]

You could just try buying a Peltier with a higher VMax.

http://www.ferrotec.com/products/thermal/modules/

Yeah, I've thought about that, but their pelts aren't much different than what we're working with now:

Model Number I Max V Max ΔT Max Qc Max W1 Dim L1 Dim L2 Dim Height
9501/242/160 B 16.00 33.30 72.00 289.00 55.00 55.00 58.00 3.45

That's their highest wattage tec and it's 33v. That would be an almost perfect TEC if it had a higher wattage but, alas, it is not to be.

Basically, I just want the greater range so I can mess with the efficiency of the pelts without having to sell my current psu's and buy a test bench psu. There's a guide here in the forum to string 2 320's together to get 24v. With a range down to, say 8v, one could range their TEC from 16v to 24v. Which, for the 437w one, would be pretty sweet.

Though, this may all be for naught as it seems frozencpu is out of stock and nobody else seems to carry the 437w TEC :ROTF:



:(

[littleowl]

hey raven did you check on ebay?

[THE JEW (RaVeN)]

Yeah, even ebay seems short on 'em. Plenty of the 350's, but I think those are rated for electrical input and not cooling capacity.

[littleowl]

get on ebay and send thermalenterprises a message! They are the ones I delt with when I got my 320w and they were really friendly.

[THE JEW (RaVeN)]

Yeah but the largest TEC I've found them to offer is their 350 watt one. Since that's the rating at 50 degrees, that's not much better than the standard DD one. I've sent them an email asking what their largest wattage pelt is so I'll get back to you on that.

This one *may* show promise for undervolting (but not large wattage):

http://www.supercool.se/default.asp?viewset=1&on='Products'&id=&initid=118&heading=Products&mainpage=templates/07.asp?sida=82

340 watts at 36volts with a rating at 25 degrees. Probably not, but unless frozencpu stocks up again, it's about the biggest one out there that I know of.

[littleowl]

ouch that 340 will not be worth a darn after you take the Voltage down!

I know when I got mine off of them, they had a 437w tec. but if you did the math it was more like a 320w I think.

[initialised]

I am no electronic engineer but I don't see why not. If you changed out the pot to a different one you should be able to adjust better IMO.I am an electronic engineer and I'll tell you why not:
The Pot on the PSU offers fine control around the standard voltage to control for local variation in supply since a 230VAC supply might be as low as 220V or as high as 240V. For example my 13.8V 500W PSU goes from a minimum 12.66 to a maxinum of 14.8. If you have 24V, 30A (720W) and you drop it to 18V using a pot then that's 6V through the resistor at 30A or 180W of heating. How about putting TECs in series?

In high power applications like this you really need to control the transformer output voltage not the SMPS output voltage. Fine control over 1-2V is OK.

KitsNParts (http://search.stores.ebay.co.uk/KitsNParts_350W_W0QQfciZQ2d1QQfclZ3QQfsnZKitsNPart sQQfsooZ1QQfsopZ1QQfsubZ3100402QQsaselZ133907672QQ sofpZ0) offer a range of DC PSUs with suitable voltage and power outputs for TEC cooling and I think they can do them to order.