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I have a 32GB, USB 2.0 ICIDU USB stick that I want to connect to my Raspi for storing ownCloud files. The stick is FAT32 formatted, from factory. My Raspi is running ownCloud 6 using this image: http://www.owncloudbook.com/owncloud-on-raspberry-pi/

When connecting the stick it gets very warm/hot after only 1 or 2 minutes (just sitting idle). Unfortunately the stick doesn't have an activity light; I can't see if my Raspi is doing anything to it. I've hooked up a simple power measuring device and the Raspi consumes 370mA on its own and jumps to 470mA with the USB stick. When the stick is connected to my Windows PC it draws about 90mA, but it does not turn warm, not even a little bit.

So the question is: what could cause the stick to warm up when connected to the Raspi, and what can I do to prevent it?

UPDATE The stick also gets hot when connected to a Windows PC while files are being copied. It is safe to assume read/write actions cause the stick to heat up. Power consumption rises from 90mA to 140mA during active periods.

I previously had the stick mounted as /var/www to store ownCloud files on it. Mounting the stick in /media/usbstick doesn't cause heat. Somehow Apache2 seems to cause constant read/write activity when the stick is mounted in /var/www

UPDATE 2 Here's what I did to keep temperature down :) USB stick with heat sink

The heat sink comes from an old 7805 voltage stabilizer. Surprisingly, it fits exactly. The stick has an aluminium casing, which helps with heat dissipation.

  • In my experience a hot USB flash drive is an indicator of a failing drive. – Steve Robillard Feb 19 '14 at 17:36
  • Steve, I've considered this. But the drive is brand new and it doesn't get warm when used under Windows. I'm currently doing some stress tests to see if I can warm it up using copy/delete/etc actions – Elmer Feb 19 '14 at 20:24
  • I've successfully lowered th temperature of USB devices (flash drive/wifi/bluetooth) by using a short usb extension cable. It provided a better heatsink, than the USB plug on the RPi as I was using a case. – Jervelund Feb 20 '14 at 9:18
  • You can use iostat or iotop, to find out what is using your flash drive – Jervelund Feb 20 '14 at 9:21
  • Nice mod! :) +1 – Piotr Kula Feb 24 '14 at 20:55
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It is not common for flash drives to get warm but it is not uncommon for USB devices to warm up quite a bit.

It is possible the MCU on the flash drive makes it get hot while you are doing lots of transferring because it has to deal with even wear leveling and smart sectoring.

As long as your device is a legitimate, FCC/ECC/EU approved device then you have nothing to worry about. If you bought it from China of eBay, then it MAY be one of those devices that were not approved, and GREY imported, and those MAY cause serious problems.

Some devices I have used can get to 60 degrees celsius . That is hot to handle but still safe. As long as you are not approaching 80 or 100 degrees celsius you are OK

  • You should be fine with that. I know its a bit worrying, but sometimes these USB devices do that and its OK, and within specification. – Piotr Kula Feb 21 '14 at 10:44
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    For good measure I've attached a heat sink of an old 7805 to the stick. Now it only gets warm :) – Elmer Feb 22 '14 at 20:46
  • Awesome :) You need to post a pic. I like to see some good modding :] – Piotr Kula Feb 22 '14 at 22:17
  • "It is not common for flash drives to get warm but it is not uncommon for USB devices to warm up quite a bit." - this is not true anymore. The new "small-profile" mini-sized USB drives that are available, esp the USB 3.0 version (from sandisk, samsung, transcend), etc all are so small that there's no space for quick heat dissipation. They do run hot with normal operation. But they have been designed with that in mind, there's nothing odd about it. – Sujay Phadke Mar 14 '15 at 23:45

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