I have one raspberry PI and two PI-2, side by side, inside a little cupboard.
I'm constantly monitoring their temperature. I'm worried because one of the Pi-2 is quite hot.
The PI and the hot PI-2 are running raspbian jessie and mostly idling.
The cool PI-2 is inside an official case (without active or passive cooling) and running OpenElec (latest stable).
I made some measurements on the Raspi1 and the hot Raspi2 a couple of months ago and everything seemed normal.
- Raspi1 prev temp: ~50C (it was cased then)
- HOT Raspi2 prev temp: ~ 40C
Now ambient temperature is quite hotter, but I wouldn't expect so much a difference:
- Raspi1 current temp: ~45-50C (it isn't inside a case anymore)
- Cool Raspi2 (cased) current temp: ~57C, seems pretty stable
- HOT Raspi2 (not cased) current temp: ~63-75C, the CPU-GPU bundle is scalding to the touch (rest of the board doesn't feel too hot)
I know the theoretical limit is at 85C but I'm worried that it has jumped from a nice temp to something near the limit, while the cased one is notably colder.
All of them are connected via HDMI to a mostly unpowered TV, and through wired ethernet to the same router. I have interchanged power sources just in case, but didn't have any effect. I also tried to disconnect HDMI and network from the hot one, but no noticeable effect.
They are not overclocked, and anyway (as already said) mostly idling.
Software: In order to compare apples to apples, I swapped the SD cards and removed the case from the cool raspi2. The cool one has gone about 15C down, now sits about 42-43 (as the other one did a couple months ago). The hot one was down by 5C, but after a few minutes got hotter than it was (to over 65). So now I know it's not a software issue or something weird caused by the case. Ambient temp is about 30C, perhaps a little more.
To test both in as equal conditions as possible, I used the same power source and even the same ethernet cable.
To test, first I let the device idling for a while and look at the measure. Then I tried to max out the CPU, opening three ssh sessions and executing one instance of "while (true) do find /; done" and two of "while (true) do ls / -R; done", besides another session with top and another with temp measurements. top indicated a sustained CPU (i.e. top us% + sys%) usage of around 90%
The hot device was consistently at about 2.0 W when idling. When maxed out it was set to 3.0 W.
The cool one was at 1.5 W when idling. When maxed out it jumped between 2 and 2.5 W.
Power consumption: I finally got a usb voltage/current tester. According to it, the cool raspi2 is consuming ~0.4 A while running an idle openelec, while the hot raspi2 (same USB power source, same cable, same SD card) is consuming around 0.75 A. Voltage is around 4.90 V in both cases. ** This seems to be the problem. ** When trying to locate the issue, sometimes after fiddling for a while, temperatures went down to normal or near normal, to be up again after a couple of days.
What should I do now that I've isolated the issue?