Ebay Products usefull or rubbish? - Page 1
Forum section: electronics / projects

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 14, 2018, 11:07:00 pm
content: sry I dont know if it show up in english or german:https://www.ebay.de/itm/Solarmodul-Solar-Solarzelle-Photovoltaik-Ladegeraet-Panels-Controller-Regulator-/14245135328030A Controller + 10W Panel EUR 29,99 good price or ripp off?or some "Peltier Refrigeration"https://www.ebay.de/itm/Thermoelectric-Peltier-Refrigeration-Halbleiter-Kuehlsystem-Kuehler-Cooler-Fan-Kit-/142637213364for EUR 12,99.One of the problem will be the both side must be separate to cool something and the other side is the hot.The requiere: 12V DC 6AA good Voltage for Solar Panel stuff. 6A are not that low power.OMG the have some with a CPU Stile cooler on top (or bottom):https://www.ebay.de/itm/12V-DIY-Semiconductor-Thermoelektrische-Peltier-Kuhlsystem-Ventilator-Kuhler-Kit-/142461536313

author: Raj
author_rank: Frequent Contributor
timestamp: July 15, 2018, 08:06:17 am
content: Ripoff i'd say.Making one by sourcing individual components from the same guys is way cheaper.Specially the peltier ones.Depending on the application,it may be cheaper to transfer the heat into a water cooling block instead of a big expensive air based heat sync

author: Siwastaja
author_rank: Super Contributor
timestamp: July 15, 2018, 10:51:23 am
content: That particular Peltier module doesn't look completely useless, but it has far too small heatsink on the hot side to be really useful. I'd expect you could run it at about half the rated power (i.e., at 9V, 4.5A), and get about 10-15W of actual cooling power out of it when cooling to about 10-15 degC below ambient. I'd guess it can't go much more than 20 deg below the ambient, no matter how carefully you insulate your things being cooled. And cooling anything down will be super slow.Really meaningful cooling is quite difficult to achieve with Peltiers. The COP is around 100% in optimal case (dT=0), which is already unremarkable compared to compressor systems achieving over 500% in similar conditions, and worse, the available cooling power diminishes linearly with the temperature difference between the sides, and is already zero at around 50-60 degC difference. This means, to get even half of the rated cooling power, temperature difference between the sides needs to be about 30 degC. Now, if you want to cool things down 20 degreesbelow the ambient, this only leaves you 10 degree difference between the ambient and the hot side - necessitating huge, well designed heatsinks. Look at a combination ofthickheatsink base which spreads the heat on a large number of fins,combinedwith a large number of fins.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 15, 2018, 12:21:47 pm
content: We have an small walk way on the roof for maintenance the could be a good spot for some Solar Panels to put there during Spring and Summer.The point is the Peltier module are 100% save and there is quite no way to explode or put out some Toxic stuff out.I found that on ebay:https://www.ebay.de/itm/Halbleiter-Kuhlluftkuhler-wassergekuhlter-Kuhler-150-60-90mm/292613979802?hash=item442126fe9a%3Ag%3Ar9EAAOSwKwBbBmAi&_sacat=0&_nkw=Peltier+pump&_from=R40&rt=nc&_trksid=m570.l1313a little bit expensive but the result look good on the picture.https://www.ebay.de/itm/12V-Thermoelektrische-Peltier-Kuhlung-DIY-Wasser-Kuhlsystem-Kuhler-Gerat-Lufter/163035917160?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D52957%26meid%3Db98b0283f5ce43a3b46affb906493a5b%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D163035917160%26itm%3D163035917160&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A094b76c3-8828-11e8-a0e8-74dbd1808ec1%7Cparentrq%3A9dd93c3d1640aa46906756e9fffbf4bb%7Ciid%3A1https://www.ebay.de/itm/120W-Thermoelektrische-Kuhler-Peltierkuhler-Halbleiter-Kuhlwasser-Kuhlsystem-/163020557497It look the Chineese hack everything together what the could find in the left over box.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 15, 2018, 12:56:08 pm
content: Quote from: Lord of nothing on July 15, 2018, 12:21:47 pmThis is absolutely stupid. They stopped using toxic, dangerous refrigerants (such as ammonia) in compressor systems about 100 years ago, and they do not just explode randomly either.The Peltier's power supply or wiring can as well catch fire, and the PVC insulation will put out very toxic smoke.Refrigeration technology is about as safe as anything can be.Note that it's often completely impractical to provide enough cooling with Peltiers for preserving foods, or keep drinks cool. Even if that is possible, the energy consumption is so high that it's an environmental disaster. When done absolutely right, it's about 10-20 times less efficient than just the normal refrigerator, but it can be much worse than that, and often is.Re: the latter Peltier module: I wouldn't use heatpipes on the Peltier's hot side. Heat pipes can transfer great amounts of heat, but the rated degC/W is not a constant but only applies at a certain high dT, since there is an evaporative action going on. While this works great when you cool things that can work at higher temperature differences (such as semiconductors, CPUs...), remember, the Peltier's hot side needs to be cooled really close to the ambient to be of any use. For example, a CPU can work fine at 80 degC, but the Peltier hot side needs to be at 30degC! Hence, I have always used either active (pumped) water cooling, or very large, thick aluminium heatsinks - copper would be even better.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 15, 2018, 01:36:47 pm
content: My Dad have an Pool who want to be hot and cosy.The Problem is onboard a Train a Compressor Style System is prohibited to use for the Chemical who get use in the cooling System.

author: Raj
author_rank: Frequent Contributor
timestamp: July 15, 2018, 02:10:10 pm
content: Peltier is for small area cooling.eg if you're cooling a small laser diode or some low tdp component.

author: towlerg
author_rank: Contributor
timestamp: July 15, 2018, 02:35:52 pm
content: In general terms, the cheap stuff you buy on eBay (typically from the far east) scams excepted, is exactly the same as the stuff you buy retail. The down side is you have to wait 4 to 6 weeks.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 15, 2018, 02:47:51 pm
content: I often buy stuff from China the are a lot cheaper.That stuff from china <1€.Local Shop:https://www.conrad.at/de/sma-adapter-sma-buchse-sma-buchse-tru-components-1-st-1579290.htmlQuotedoes the sound based cooling stuff is still to the market?

author: Raj
author_rank: Frequent Contributor
timestamp: July 15, 2018, 02:58:42 pm
content: Oh,buying assembled stuff from china is affordable but buying components from them to make the same stuff is cheaper.I've never herd of any commercial accoustic referigration.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 15, 2018, 03:22:27 pm
content: The big pro with Ebay is I can order many think from arround the World who are here not available.Like Stuff for Police and Military. I got an Door Breaking Tool from US who here are just sold directly to Law enforcement Units.Shipping and Import was just some € for.Which option do I have for cooling an small IT Compartment with Solar?

author: Raj
author_rank: Frequent Contributor
timestamp: July 15, 2018, 04:00:01 pm
content: So you want to cool electronics for solar, like charge controller ,right?How about you contact a machine shop to make you a better beefier enclosure with better airflow ? or just put a water block,connect just one pipe to it and block the outlet port and to the other end of pipe,put a resevoir. If that isn't enough,connect 2 pipes and let the convection do the job.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 15, 2018, 05:54:19 pm
content: ...I have to cool an Enclosure who its get very hot during the Day at the moment.There is no way to get cool Air there without cutting a hole in the Roof.The best way is Solar Cells (my Dad kill me if he know I would power some AC over the Main Powerline) and something who never could burn, explode,....

author: towlerg
author_rank: Contributor
timestamp: July 16, 2018, 11:29:55 am
content: I have to know why you wanted a door breaker?

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 16, 2018, 02:26:45 pm
content: Because it get nectary to have one?

author: Raj
author_rank: Frequent Contributor
timestamp: July 16, 2018, 03:21:12 pm
content: Oh I said,you should employ motorless water evaporation cooling.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 16, 2018, 03:45:23 pm
content: ... Again. Its a Server rack who is under the Roof(top). There is burning Hot.So where should the Water evaporate? And the chilling effect is not that much to get it from 45C to 30C.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 16, 2018, 04:12:03 pm
content: No, you can't cool a server rack with peltiers.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 04:13:07 pm
content: A server rack is likely going to dissipate a few hundred Watts, that is orders of magnitude more than you can reasonably hope to carry away with a Peltier.

author: Raj
author_rank: Frequent Contributor
timestamp: July 16, 2018, 04:30:39 pm
content: What temperature is it at,right now? What temperature do you need?Most electronics can take upto 80 degrees concidering that they have crappy capacitors, Silicon can take even higher temperatures.If it's so hot,Then add a pump and a radiator to the loop

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 16, 2018, 10:14:48 pm
content: QuoteI dont know I put there just the Server Rack. I wait for a replay from a Company if there product can do that I want to do.If the work I put just an Converter there who transfer the USB Data to my Server.I need an normal Temperature the best think is when the is stable. Thats ~25C in Summer.Sure this Summer is Temp is very low so an Active Cooling is not necarcary yet.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 16, 2018, 10:54:16 pm
content: Lord, numbers are your friends. Look at your own first post. They are selling a 30 A controller and a 10W panel. Ten watts at 30 amps is 0.33 V. This company didn't match their components, they just had a mix of surplus parts that they are throwing together.If you understand the limitations and capabilities this could be a good value, but you will have to supply other things to make use of it. Your questions don't give confidence that you can achieve this.Numbers help also in evaluating your problem. You should know how much power your server rack is consuming. You can estimate the thermal resistance (measured in deg C per Watt) from the server to the environment in a number of ways. The easiest is just to measure the temperature outside and at your server location on a cloudy day and use the power number you already know. This will let you predict the temperature on hotter days (although this assumes the server heat load dominates, not usually the case if the sun hits the roof at all). But You can compensate for this by measuring actual temperature on sunny day and using that to estimate the solar heat load. This is all grossly simplified, but will get you in the ball park.Now you know the cooling power required. Your proposed Peltier device consumes 6 A at 12 Volts or 72 Watts. (Do you see a problem with the 10 W panel?). As a prior poster says the COP is at best 1, so you can't get more than 72 Watts of cooling. How does this compare with your needed cooling power.You can just buy a bunch of stuff and throw it together and see what works. But often it won't work and will discourage you. Better to understand where you are going. Doing this stuff without numbers is kind of like riding a bicycle at night without a flashlight.