here is the website I will be referencing: http://www.instructables.com/id/5-Mini-USB-Fridge!/

So I was reading from Inscrutables on powering a small Peltier TEC to cool your hand while reading, and so I bought a 5v 19.4 Watt Peltier.

The instruction website got me under the impression that a peltier will run at the 5 Volt and whatever current it receives. So, I set up the peltier element using my USB cable plugged into a USB battery pack and nothing happened. The item and fan turned on for one second, then shut right back off.

I got a current reading of 5v, 3.9 Amps when I plugged the Peltier USB into a USB wall wart which confused me since the maximum output of the USB cable and charger is stated to be 5V 2.4 Amps. So logically, I need to find some way to power the Peltier off of a rechargeable battery 5v 2.4 Amps.

  • According to the instruction website I should have been totally fine powering the peltier from a USB battery pack as the instructional sheet was using a 12v 60 Watt peltier element powered by a USB cable.

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Potential Solution and Question


I believe the problem lies in that the USB battery pack is shutting off to save itself from outputting a current of 3.9 Amps when it can only reasonably allow a draw of 2.4 Amps.

  • How can I stop this, how can I make it so that the peltier runs off the USB battery pack at its maximum capacity of 2.4 Amps, 5 Volts?

  • And why is the peltier pulling 3.9 Amps and not defaulting to the 2.4 Amps I am giving it through the rechargeable battery pack, as did the peltier powered by the USB cable in the Instructables website?


1 Answer 1


You bought an element rated for 5 V 20 W. This means that it will draw ~4 A when connected to 5 V stable supply. Period. It won't draw more. It won't draw less. There is nothing you can do about this, it is practically a ~1.2 Ohms resistor. The Peltier is not "defaulting" to anything because it has no idea that someone has some limit.

To get your Peltier battery to run at 2.4 A from 5 V, you need to get an element rated for 5 V 12 W. Or get the element as suggested in the video, 12V-60W, which comes down to resistance of 2.4 Ohm.

And yes, the charger likely shuts down at 3.9 A.

  • \$\begingroup\$ Hey Ali Chen, so are you saying that if I get a 12V 60W peltier and run it from the USB battery pack, it will work? I am really new to electricity and trying to understand all of this. If so, what configuration of power (12V, What Watt) would I need to achieve the maximum output possible from the 5V 2.4A battery pack? Thanks \$\endgroup\$ Sep 10, 2017 at 4:44
  • \$\begingroup\$ @OmarSumadi, I don't know about "maximum" and "possible", I am saying that 12V/60W peltier will work just fine from 5V source, and won't overload your charger. For other ideas about loading and thermal performance you need to look into application notes like this one, cui.com/catalog/resource/peltier-app-note.pdf \$\endgroup\$ Sep 10, 2017 at 5:05
  • \$\begingroup\$ Hey Ali, I guess one thing I want to ask you. Would a 12V/72Watt Peltier overload my charger? 12V/6 Amp = 2, I = 5/2 = 2.5 AMPS at 5V, do you think this will be okay? \$\endgroup\$ Sep 10, 2017 at 5:17
  • \$\begingroup\$ @OmarSumadi, yes, the 12V/72W looks okay to me. \$\endgroup\$ Sep 10, 2017 at 5:34
  • \$\begingroup\$ I have a quick question that will wrap up everything, and I appreciate you help so much you have solved so many problems thank you thank you thank you! So, the question: If I have this same 2.4A 5V Max Output battery pack, and I buy a 12V, 60 Watt Peltier Element and a 5V .5A computer fan (leaving room for comfort, item is actually 5v .36A), could I run both off of that one battery pack? For Further clarification, I will split the USB cable two ways, and using OHM's law the peltier will run 5V 2A. Then I have 2A + .5A = 2.5A! \$\endgroup\$ Sep 10, 2017 at 20:36

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