Pi Undervoltage/power issues: I had a strange lightning bolt/temperature symbol with an exclamation mark popup in my navbar, what does that mean?

Well, that's not really my decision since I didn't code OctoPrint.

What I do, though, is I buy used APC UPSs at flea markets or someone's garage sale. They're heavy since they include a 12V acid battery inside like you might find in a car so anyone is delighted to get rid of them for almost nothing (even free).

At about the five-year point, the battery needs to be replaced but you can get them locally for about $24 but they'll give you about $5 back as a core fee for the replacement battery you bring back to them. Replacing the battery is about the easiest thing you've ever done.

From time to time I get the grey undervoltage symbol despite the Pi is powered by a PC PS at about 5.4V.
Is this occurrence of the undervoltage logged somewhere? I assume in the octoprint.log, yes?

Yes. It should log any kind of detection events in there. I think it also logs when everything is normal again.

Thank you! I'll check after the running print job when and why it occurred...

For this issue also occurred in idle mode, I further investigated and found a quite bad connection within my "Power Supply & OctoPrint Unit".
"Problem erkannt - Problem gebannt" :sunglasses:

Is there any possibilities how to reset this symbol without rebooting during printing (to check if show again) or show history when happen this problem and when missing?

The history of these events will be in both the octoprint.log as well as the /var/log/syslog if you were interested in seeing them.

The existence of any undervoltage condition puts your microSD card's second partition at risk for corruption as well as serial-related problems, etc. The duration of each event would further be a factor. Note that this doesn't tell you how much under 4.64VDC the input voltage dropped, just that it did so. And yet, this is also a factor. Behind-the-scenes, there is a magic voltage that indicates the threshold between a digital zero and a digital one on the 3.3V data logic lines. The lower the input voltage, the more likely that bad decisions will be made internally by the Pi.

cat /var/log/syslog | grep oltage

Sep  1 06:25:07 raspberrypi kernel: [3316534.286203] Voltage normalised (0x00000000)
Sep  1 07:05:03 raspberrypi kernel: [3318930.470847] Under-voltage detected! (0x00050005)
Sep  1 07:05:08 raspberrypi kernel: [3318934.630893] Voltage normalised (0x00000000)
Sep  1 07:08:58 raspberrypi kernel: [3319165.512990] Under-voltage detected! (0x00050005)
Sep  1 07:09:03 raspberrypi kernel: [3319169.672947] Voltage normalised (0x00000000)
Sep  1 07:09:11 raspberrypi kernel: [3319177.993172] Under-voltage detected! (0x00050005)
Sep  1 07:09:17 raspberrypi kernel: [3319184.233224] Voltage normalised (0x00000000)
Sep  1 07:09:23 raspberrypi kernel: [3319190.473113] Under-voltage detected! (0x00050005)
Sep  1 07:09:28 raspberrypi kernel: [3319194.633162] Voltage normalised (0x00000000)
Sep  1 07:10:18 raspberrypi kernel: [3319244.553560] Under-voltage detected! (0x00050005)
Sep  1 07:10:32 raspberrypi kernel: [3319259.113651] Voltage normalised (0x00000000)

Thanks for explanation
My problem its not undervoltage but overheating
I´m interesting how to reset this overheating symbol in navbar during printing over SSH or other way?
For checking of syslog is possible to use grep heat?


You can't. The symbols rely on what vcgencmd get_throttled reports back, and that reports past event since last boot. AFAIK there's no way to change that.

Check the logs if you need a history, as @OutsourcedGuru pointed out it's all in there.

Also: if this symbol appears often or always, there is really an issue with the power supply/overheating that should be removed.

1 Like

I wish they would turn this feature off. It is annoying and isn't accurate. I have a very good 5 volt 4 amp supply going to it and this still comes on. I have used the power supply that you buy with the Pi, still comes on. I don't trust it. I have been seeing this icon for years with no issues.

I think it's very accurate. Since I removed a bad connection in my setup, I never hat that symbol again.
Do you connect power via USB port or directly to the GPIO. Do you have some devices to the PI's USB ports that draw some more current. Have you checked the voltage beyond the USB port?

I have 4 of these running octoprint servers. I use the port dedicated for the power supply. The only things connected are the printer (which supplies its own power) and a webcam. All 4 units show this symbol, using larger power supplies or the ones sold for the Pi. I have had the symbol show up with nothing plugged into it...using the power supply sent with the unit.

So each has a own 5V/4A power supply.
Maybe the power supplies do not reach the given specs?

1 Like

"They"? :thinking:

You should take accuracy issues up with the Raspberry Pi Foundation - OctoPrint's undervoltage and overheat detection is exclusively relying on data reported by the vcgen get_throttled command.

From personal experience, adding this warning has greatly reduced the support overhead caused by people running into browning out issues due to bad power supplies and similar easy to solve but hard to diagnose issues.


I know the source of the issue isn't built by Octoprint, but by Raspberry Pi, you still have to write the code to make it appear on the interface. It would be nice if it could be turned off, especially if you aren't having issues with it.
I will admit, some of this is because it plays on my OCD. If I see that, I feel there is a real threat. It just seems the perimeters set in the board are very sensitive and alert you when there is no real threat. I have been seeing this symbol for years and have never had an issue, ever.

This wasn't meant to be a dig on Octoprint, it is a great software and I think you should be charging for it. I just with there was an off button for that alert.


If I added an easy way to turn it off, people would do the same with it they already do with the printer safety warning - turn it off, because "I'll fix that later" or "It's wrong". Contrary to that warning though, turning it off immediately increases my support overhead. Which affects everyone else, because the more support the less time for bug fixing and updates. And frankly, also my sanity.


Now troubleshoot this as an electrician would. You've indicated that providing a 5V @ 4A power supply is still throwing an undervolt condition on a naked Raspberry Pi 3B, right?

  • First things first, the microUSB power connector for a Raspi 3B is rated for 2.1A by the specifications (even though a Pi wants 2.5A). This is why the connector was upgraded to a USB-C for the 4B Pi, rated for 3A. So how are you getting this 4A to the Pi? The current wisdom would be to bring that 5V input to the Pi3B by bypassing the microUSB connector.
  • I know of no 4A 5V power adapters out here in this space. You should link the product. Are you sure it isn't a 5V charger rather than a power adapter? A charger provides pulsing DC rather than continuous.
  • Is this power adapter plugged into a UPS? If so, then you are more likely to receive the full amount of AC power to the plug of the Pi's power adapter in the first place. What if the power at the wall outlet is low? I've re-wired many many power outlets and actual building wiring to know how bad it can be. I've seen 106VAC out of a 120VAC outlet in a business building. If you plugged a 5V power adapter into that you'd see 5V - 0.6V = 4.4V and the Pi's cutoff is 4.64V. As a result you'd get your undervoltage condition no matter what's plugged into the Pi and no matter what kind of power adapter you tried to use.

The indicator also appears when the Raspberry Pi is connected to a printer, the printer is off and the Pi is on and when the logic section of the printer board is connected to the USB port. The Pi tries to power the printer logic section incl. the LCD. This lets the voltage of the Pi drop drastically.

To prevent this, either do this: Put tape on the 5V pin - Why and how, break the 5V line in the USB cable or, if possible, disconnect the USB 5V connector from the printer logic section - usually a jumper. This last one is not supported by all boards.

@Ewald_Ikemann Good point, I've quoted that up in the OP.

1 Like