I’ll measure that for you today when I charge again. (Could you make it a bottle of Nero d’Avola instead? 
)
Edit: spelling
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Ah! This topic is getting expensive!
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With wifi and mobile settings on, I started charging at 40% with the phone placed on a mostly non-heat-conductive surface (so as to avoid heating or cooling the phone’s exterior).
Thermals at beginning of charging time:
Two hours later (approximately 80% charge):
At 90% charge, I initiated the following:
.short 4-second .mp4 on repeat, display constant/on
.Firefox open in background
.streaming music on continuous play
.a few terminal commands and install
.software store check for updates
A short time later, at 95% charge, the red LED started blinking, so I unplugged and took the following readings (left/right = as facing screen):
Screen, center: 43.9° C
Left edge, lower: 26.4° C
Left edge, upper: 28.3° C
Top edge: 27.0° C
Right edge, upper: 27.4° C
Right edge, lower: 28.4° C
Bottom edge: 26.3° C
Back cover, center: 40.2° C
Battery surface, back removed: 39.7° C
Modem cover: 40.7° C
Wifi/BT card cover: 42.0° C
Thermals:
Powered off, then 17 minutes later:
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Great job!
Funny, I bet that the sides were warmer.
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Maybe so. The frame is, after all, essentially a heat sink.
It was definitely starting to overheat with all those processes running while also charging.
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For what it’s worth, the blinking red LED while charging means that the charging controller did its job and paused charging due to high battery temperature (I don’t remember the exact threshold but IIRC it was slightly above 40°C). There’s no need to unplug it in such condition since the charging is already stopped and the phone stays powered from USB, so the battery stays mostly unused (at least unless there’s a power peak that can’t be handled by USB alone). After unplugging you start to draw power from the battery back.
The CPU is set to start thermal throttling at 50°C - first by limiting the frequency to 1.0GHz, and then starting at 60°C by idle injection. Additionally, the GPU gets throttled at 65°C as well. The critical temperature at which the SoC is forcibly shut down is 90°C (I have hit that in the past on devkit and some early batches when compiling some big stuff, but so far never on Dogwood or Evergreen). These values are set in the device tree: https://source.puri.sm/Librem5/linux-next/-/blob/pureos/byzantium/arch/arm64/boot/dts/freescale/imx8mq.dtsi#L246
Since the CPU throttling temperature is higher than maximum charging temperature, it’s perfectly normal for blinking LED to happen when the SoC is under prolonged load - inevitably some of that heat will start to reach the battery at some point (and charging will make it heat up on its own as well, so it will happen faster while charging). Usually it’s enough to just stop the CPU activity and lock the screen for it to resume charging after a short moment - of course that depends on external conditions since the heat has to escape somewhere, so don’t wrap you phone with warm blankets in such condition 
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Thanks for the explanation, @dos …good stuff. I usually try to stop charging at around 80-85%, when I catch it in time, just to hopefully extend the battery’s useful lifetime. Then again, I’m not relying on the L5 to get me through the day, like some here are.
What we need is a nitrogen-cooled phone case for the L5. 
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It would be good if that info could find its way into: https://docs.puri.sm/Librem_5/Troubleshooting/LEDs.html
(I would do it but I think that area is not community-editable.)
So right now “flashing red” means “Contact Purism” whereas at least a customer could go into Usage / Thermals and decide whether the likely cause is over-temperature, or instead it is really something that the customer can’t do anything further with without contacting Purism.
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You’re right, that part of the docs needs to be clarified.
FYI, these docs live in https://source.puri.sm/Librem5/librem5-user-docs-common where issues and merge requests can be created.
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Merge request has been created, I think.
I’m not at all familiar with “rST” markup, so nothing flashy (pun intended), I’m afraid. (Is it just me or are there too many markup languages in the world?)
Oh crap, now I’m experiencing the “85°C problem”.
I did apply the latest updates this morning (in amber) as well as install Megapixels and related recommended packages. I’m suspecting the former, not Megapixels.
Assuming this is just a cosmetic problem, unfortunately it is going to undermine what I just wrote for troubleshooting a flashing red LED.
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I don’t know whether there is something else that I need to do but the merge request is: https://source.puri.sm/Librem5/librem5-user-docs-common/-/merge_requests/39
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@fiacco, when you have time you can read output (compare it with Thermal Zones readings from Usage app) from $ sensors as well, after $ sudo apt install lm-sensors. Start readings with cold Librem 5 (make screenshot of current ambient temperatures), repeat those after some time (make another screenshot, etc.). Running $ sudo sensors-detect would be optional (not helpful here, I guess).
Also, please install Videos over PureOS Store, stream Euronews over Wi-Fi (while charging your phone) for 5 or 10 minutes (by selecting it under Channels), repeat $ sensors current reading.
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Room temperature dropped around 24° in the last days, therefore L5 values are less worrying. I did some measurement, however sensors readings match the usage values, even regarding the 85°C issue. Some examples:
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I think this issue is affecting me now, but I don’t think anyone has mentioned the issue with unplugging the charge cable that seems to coincide with it.
I had the phone plugged and idle and it notified me of an incoming SMS message. The red LED was flashing, which was perhaps not surprising as the room temperature was 27°C. I unplugged the charge cable in order to pick up the phone and read the SMS message, but as soon as I unplugged the cable, the phone instantly powered off.
I pressed the power button and the green LED lit. Once it was booted up again, the SMS message had been lost and I had to ask for it to be sent again.
I then plugged the phone back in, got the flashing red LED again and got an SMS notification (the reply to my request to re-send the message). I unplugged the phone to read the message and once again it instantly powered off.
After booting back up for the second time, the SMS message was, again, lost and I had to request it to be sent a third time! This time, lesson learnt, I did not plug the phone back in. At this point, Usage reported the charger was at 85°C. It then fell to a lower temperature, but has since returned to 85°C, with the battery temperature steadily increasing; 41.9, 42, 43…
I dampened a tissue with isopropyl alcohol and placed it over the screen, near the top, over the CPU. This quickly halted and then reversed the increase in the battery temperature. I waited for it to fall below 40°C, which required the assistance of an electric desk fan on low speed. I was hoping that the charger might fall below 85°C when the battery fell below 40°C, but this did not happen. The CPU, VPU and GPU remained at 45.00°C throughout. I then shut down the phone, and powered it back up again, removing the cooling solution only for as long as was necessary to avoid unwanted touch inputs during the process. After the reboot, the charger was still at 85°C, the battery was at 33°C and the CPU, VPU and GPU were all at 33°C. The battery temperature began to climb again. I have my doubts that the CPU, VPU and GPU temperatures are correctly updating. I terminated the experiment.
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This happen you with Amber or Byzantium?
The original L5 charger/cable is come with Power Delivery Technologies. This protocol PD helps preserve battery life by monitoring the temperature of the battery constantly by using a dynamic mode charge. Also track the overall temperature of the phone to prevent damage.
It is important to charge the Librem 5 with a charger and cable certified for Power delivery, to get all the benefits of PD.
Librem 5 still need some optimization to work like a charm, that is why there are still many things that do not work well such as the temperature, GPU, VPU, CPU or that the battery lasts for many hours with the phone on, but the Purism team is doing exellent work for constantly optimizing the device. I am using byzantium to get quick updates/optimization.
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I’m using Amber, with the original Purism-supplied cable and mains adapter. I just wanted to add my experience to the body of knowledge.
By the way, my work-around is to shut down the phone, remove the battery, then put the battery back in again and charge the phone while it is switched off. (Which may already have been mentioned.)
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@carlosgonz, do you also see that bq25890-charger showing 85°C with Usage app in correlation to Linux kernel 5.12.0-1-librem5 (on Byzantium)? Asking while think that on screen number/error of 85°C (that doesn’t have anything to do with real temperature) might already be past issue, hopefully already corrected.
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Yes i have same issues random without charging the batt, i think there is a bug of 85C temp .
Byzantium.
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@dos It seems my merge request is unloved. 
I don’t know whether that’s because I needed to do something else or you are too busy or someone else was supposed to do it. The merge request says: Ask someone with write access to this repository to merge this request. But I don’t know who has write access or how I am supposed to “ask”.
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I’d rather say that the whole docs repo is rather unloved at the moment, since we lack a dedicated person that would take care of it. I’ll try to take care of your MR in a spare moment.
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