Peltier Rating? - Page 1
Forum section: electronics / projects

author: wilheldp
author_rank: Regular Contributor
timestamp: January 25, 2014, 01:13:22 am
content: I was at the local thrift store today hunting a cheap heating element (picked up a 1,500 watt electric kettle for $5), and spotted something interesting (also for $5). It was a USB can cooler from CoolItSystems.com. Just by checking it out, I could tell it was just a peltier with an exposed aluminum plate, heat sink on the bottom, and a tiny fan to blow across the heat sink.I get it home, plug it into my iPad charger (rated for 2A at 5V) and watch it through the E4. The cooling surface got to about 27 degF, but the exposed part of the heat sink didn't get over about 80 degF. I really think this thing is capable of more. I took the aluminum plate off the top to check for markings on the peltier, but no dice. There is thermal paste on it, but I can't see any markings. It seems to be more well bonded to the heat sink (lots more paste), so I'd prefer not to take that apart. Is there any way I can tell what the max voltage or power rating of this peltier is?

author: Psi
author_rank: Super Contributor
timestamp: January 25, 2014, 01:18:02 am
content: Afaik pelteirs are rated in max current and max delta temp between each side.I have a generic one here somewhere that's around 40x40mm, from memory it's max 8A and max 60deg delta

author: wilheldp
author_rank: Regular Contributor
timestamp: January 25, 2014, 01:47:40 am
content: All the ones I have found for sale are rated in terms of voltage and power, not current.

author: w2aew
author_rank: Super Contributor
timestamp: January 25, 2014, 03:16:09 am
content: You got over 50C delta for an inexpensive device designed for USB, probably about as good as it gets.

author: wilheldp
author_rank: Regular Contributor
timestamp: January 25, 2014, 03:40:26 am
content: Quote from: w2aew on January 25, 2014, 03:16:09 amNot to split hairs, but it was 53F (12C) delta. I'd be thrilled with 50C. It was $5, so I wouldn't be heartbroken if I couldn't get anything out of it, and I will break it trying to get more. But I just think it was being severely under driven at 5V and 1.2A (it's rated specs according to CoolIt). I'll play with it more tomorrow and see what it can do.

author: c4757p
author_rank: Super Contributor
timestamp: January 25, 2014, 03:50:56 am
content: Quote from: wilheldp on January 25, 2014, 03:40:26 amDoesn't quite work that way...27F = -2.78C80F = 26.67C50 delta F = 29.45 delta C

author: wilheldp
author_rank: Regular Contributor
timestamp: January 25, 2014, 04:04:55 am
content: Quote from: c4757p on January 25, 2014, 03:50:56 amTouche...but that's still less than 50C. Like I said, I'm just playing with this thing and wanted to know if there was a way to figure out its specs short of pumping power into it until it breaks. I have no intended purpose for it. I still think $5 was a good deal for a peltier, even if it's not a terribly good one. The cheapest module on DigiKey is $13, and it doesn't include a heat sink or tiny little fan. I will post pics of this thing tomorrow. I've never seen a fan as small as the one in this cooler.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 25, 2014, 04:59:29 am
content: Get data sheets on similar devices from the couple of major suppliers. Your's should be similar if you match the size and thickness and number of thermocouples. They are the most horrendously inefficient things imaginable, but work great for certain applications.

author: SeanB
author_rank: Super Contributor
timestamp: January 25, 2014, 05:51:17 am
content: Basically the same size cheap unit has a similar rating. Likely only going to either be able to move either 20W with zero temperature drop OR have the close to 30C at near zero power transfer. They really are best at keeping a semiconductor device cooler than ambient by a small amount. If you use a multistack array you can get down to cryogenic temperatures with a very small load like a thermal camera sensor in a very well insulated casing, not much more. As a can cooler it is not very good. Cooling water in a small water cooler is about the best, though you will be hard pressed to get more than 2 cold cups per hour.

author: Skimask
author_rank: Super Contributor
timestamp: January 25, 2014, 06:41:47 am
content: Got a 10pack of 40mm x 40mm peltier chips off ebay a few weeks ago for something like $20. As far as I can tell, most of the 40mm x 40mm types are rated for 12v @ 7amps, 84watts. I haven't pushed mine that hard yet.Put the power supply on a single chip and gingerly pushed the power to it. Got it up to 25watts (roughly 8.3v @ 3 amps). The bare cold side got down 5F, hot side with a small 40mm fan and matching heat sink only got a couple degrees above ambient.Put a heat sink on the cold side, isolated the airflow between the side, as well as around the cold side sink. Not a lot of heat (cold?) capacity of a single chip. With this setup, cold side would only get down to 40F.As stated above, terribly inefficient as far as anything goes.I plan on using all 10 chips in an MCU controlled 'thermal chamber'. Start off small-ish, and work my way up to as big of a box as the chips will keep cold and/or warm...or at least as big as whatever power supply and MOSFETs I get to run it will handle without letting out the magic smoke.

author: rexxar
author_rank: Frequent Contributor
timestamp: January 25, 2014, 06:26:35 pm
content: The temperature differential for peltier devices increases with voltage. The only question is what the maximum safe voltage for your device is. A good datasheet from a similar device will give you a graph of deltaT vs voltage. The characteristics of peltier devices of the same size are usually pretty similar, so find two or three datasheets for devices of the same size, and compare.

author: Zero999
author_rank: Super Contributor
timestamp: January 25, 2014, 06:49:18 pm
content: Quote from: SeanB on January 25, 2014, 05:51:17 amYes, thermoelectric coolers are small lightweight, have no moving parts and don't contain and gasses but are horribly inefficient which is why traditional vapour phase coolers are used in water coolers.