Cooling your Raspberry Pi – reasonable or a waste?

There are plenty of radiators and fans for the small single-board computer – but how big is the impact of using cooling? Don’t get me wrong – having a cooling system is always better than having no cooling at all. But I was curious about the exact difference with the current top model (RPi 4B, 4 GB).

First of all it is good to know in which temperature ranges the computer can be used at all. The Raspberry Pi Foundation names the following values in their FAQs:

  • LAN-Chip: 0 to 70 C°
  • SoC: -40 C° to +85 C°

So, using the device in Oimjakon and Werchojansk is not an option at all. 🙂

But even at home using a cooling system is – depending on the load profile – a good idea or necessary as the test showed up.

The tests were executed on a Raspberry Pi 2 and Pi 4 running Raspbian Buster (unfortunately, I had no Pi 3 around for testing). For the kernel I was using the version 4.19.97-v7+ released by the foundation and the last beta release 5.4.40-v7+. The results were the same when using the same firmware; some things have changed here in the last months as the Raspberry Pi Foundation blog reports.

Beside the Idle value I also measured temperature after a 15 minute burn-in-test and 1 minute and 10 minutes after finishing the test. For generating load, I was using stress-ng:

# stress-ng --matrix 0 -t 15m
Using –matrix 0 all available CPU cores are used, -t 15m sets the time limit to 15 minutes.

Afterwards I assembled the Pis in a simple acrylic case with 40mm fans – the fans don’t have any kind of control mechanism, they always run on maximal power.

Simple acrylic case with 40mm fans

Here are the test results:

Setup Test Pi 2 Pi 4
without radiators Idle 45 C° 59 C°
15 minutes burn-in 70 C° 83 C°
After 1 minute 55 C° 72 C°
After 10 minutes 48 C° 63 C°
Radiators and 40mm fan Idle 30 C° 37 C°
15 minutes burn-in 32 C° 56 C°
After 1 minute 31 C° 43 C°
After 10 minutes 30 C° 37 C°

I was highly suprised to see that the Pi 4 always generates a lot of heat during idle and quickly (after approximately 6 minutes) nearly hits the SoC limits. During long-term usage the hardware might get corrupted pretty soon. I was using previous Pi generations mostly without radiators – definitely a bad idea for the Pi 4.

So better invest additional 5 bucks for radiators and fans. 🙂

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    • Hey Matthias,

      I’m using the ICYBOX IB-RP406 which comes with some simple radiators and 40mm fans. I guess any fan will do the trick if it’s just a simple fan without any speed control.

      Best wishes – stay healthy,
      Christian!

  1. Hi Christian,

    I just tested the stress test with my passive cooling case during the lunch break 🙂
    It is a Pi4. Just started it freshly, let it run for half an hour or so – there are barely tasks on it right now.
    I used following Command to keep track of the temp:
    while endless=0; do echo `date +%T` Uhr: `vcgencmd measure_temp`; sleep 10; done
    Idle Temp: 38°C
    After 5 Mins Test: 55°C
    After 10 Mins Test: 60°C
    After 15 Mins Test: 63°C
    Cooling 1 Min later: 54°C
    Cooling 5 Mins later: 49°C
    Cooling 10 Mins later: 47°C
    I think that is also quite neat, regarding the lower power consumption due to additional fans!
    Also our results may defer due to different ambient temperatures in our flats or generally speaking the weather 🙂
    Thanks for the article again!

    • Hey Stani,

      that’s an interesting differnce between your and my measurements using the same device.

      So the room temperature seems to have a huge impact on the device. Next time, I’m mounting my Pi in the fridge. 😀

      Thanks for the feedback!

      Best wishes,
      Stanki

  2. don’t forget to think about the temperature envelope for the SD-Card you are using. These are the ones that die first, if the temperature is not transported away from them.

    So having a fan near the radiators of CPU and RAM may help them, but if people put their RPi in cases, you have to get the air out there as well.

    • Hey Jan,

      good point – totally missed that!

      I really need to get a different case for my two remaining Pis without fans.. 🙂

      Best wishes,
      Christian.

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