Full ack.
That's like turning your music louder if your car makes funny noises or putting a sticker over the "check engine" light...
4 Likes
I found mine worked until I installed a lot of plugins, I solved the problem by buying the official Pi power supply, you need to increase the capability of your power supply. I would also use a cable that can carry the current, you may have voltage loss across your cable and connector.
3 Likes
Get a voltmeter and stop guessing 
You can get one that's plenty accurate enough for this sort of thing for $10. E.g., Portable Electrical Digital Multimeter Handheld LCD Voltmeter Volt Backlight DC AC Ammeter Voltmeter Ohm Tester Meter|Voltage Meters| - AliExpress
Measure your voltage on the Pi side and adjust/replace the power supply, USB cable or Pi as needed. For a fixed output power supply, look for one that says 5.2V. The .2V accounts for normal voltage drop in the cable.
I have tried 4 of the "Official Raspberry 3B Power Supplies" that claimed to putout various voltage and amperage....all of which were BS. I eventually hooked it to my desktop power supply and got the warnings to stop dialed in at 5v, 3.3a. They mostly disappeared at 5v,3a, but would occassionaly still pop the warning. Just so you know, I do not try to power my printer from my Pi. All I have hooked to it is a small Pi camera, and a 5v fan hooked to the GPIO pins. On the advice of someone on another forum, I took a chance on the power supply below. When I tested it at the plug, I got 5.1v, 3.1a. So I figured I'd take the chance. So far, it's been on my Pi for almost 4 weeks, and I have not seen any under-voltage issues show themselves. I'll see how long it lasts, but for now, it's doing good.
https://www.amazon.com/gp/product/B01N336XEU/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Mackertop 5.25V 3A Micro USB Wall Charger AC Adapter for Raspberry Pi 3, HP HSTNN-LA43 PA-1150-22HA, Android Tablet Smart Phones with 1.5M (4.9 ft) Po https://www.amazon.com/dp/B01HB44IE6/ref=cm_sw_r_cp_apip_VcwCDJ9FpGnbf
This power supply works perfectly for the 3B+. I have hade zero issues with it. See it they make one for the Pi4 plug.
For what? It’s been running octoprint for 2+ years and another custom app/pi on my outside generator on my home that monitors that. Over a year in cold and hot temps and still running….. no issues and no lightning bolt.
1 Like
Then you are lucky.
Chargers often do not run such reliable.
I solved my issue after days of head banging.
Cut open the cable, selected the red wire cut out an inch so if it tries to grow back together it would take a long time. Sealed the cut with electrical tape and the problem has not reoccurred.
Now I have a new issue with
Loud noice from gantry when starting my RaspberryPi 3B when connected to printer. Like gears are grinding.
2 Likes
So it doesn't happen when you boot the pi while it is disconnected from the printer and connect it afterwards?
Doesn’t happen when I boot Pi, but after I connect printer I get the “low voltage error”. Cutting the red wire stopped the error.
I had a similar under-voltage issue with one of my OctoPis, I troubleshooted everything else in detail first but in my scenario it turned out to be the USB lead itself! 
I replaced that and it disappeared from thence forth.
Power-supplies are naturally one to focus on and worth while trying a different one if you have one to hand, but don't neglect to just try a different USB cable as well.
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I have had this alot since V1.5 and thought it was a bug, Tried everything like tape on the 5v USB, New cables. power supplies the lot and it turned out to be a feked Pi.
I had a Pi running on another printer that never had the issue and swapped everything over one by one and only when I replaced the board did the UV error stop.
Hi,
I also had a permanent undervoltage warning on both of my OctoPIs running on Pi 3B+.
To be sure the power supply is not causing the problem I connected the Pi to my Lab power supply set to 5.2V and 5A and connected the power to the GPIO directly. But the undervoltage warning was still coming up.
So I decided this is a OctoPI problem and just disabled the Pi Support Plugin. Since that everything is running smoothly.
One of the PIs is running for more than a year but the problems appered when I upgraded my system to the new OctoPI version with latest Python.
So I thinkt these permenant undervoltage warnings are a bug, not a feature.
Best regards
Onki
Then it's more a problem of your RasPi than a OctoPi problem. For most of the users it is running fine. I have no issues with a 3B´and a 4B
bold decision...
Yeah since I taped off the check engine light in my car it is also running smoothly.
There must be something wrong with that light - not with my car
3 Likes
It has been mentioned above that OctoPrint just reports the result of a check which the raspberry does on it's own.
You can get those results from the commandline, no need to run OctoPrint for it.
With the command:
/opt/vc/bin/vcgencmd get_throttled
If the answer is:
throttled=0x0
You're good with the supplied voltage and SoC temperature.
The bits on the returned number mean:
Bit Hex value Meaning
0 1 Under-voltage detected
1 2 Arm frequency capped
2 4 Currently throttled
3 8 Soft temperature limit active
16 10000 Under-voltage has occurred
17 20000 Arm frequency capping has occurred
18 40000 Throttling has occurred
19 80000 Soft temperature limit has occurred
A value of 0x50000 means 16 & 18 -- from the boot moment up to now Under-Voltage has ocurred at some point as well as Throrrling has occured.
If the power supply is right then it may be your cable is faulty. The warnings from the Pi are important, you could have a faulty Pi but it has happened hundreds of times before and it is usually the power supply or cables/plug. I had the problems, all worked well till I installed more plugins, I changed the power supply for an official Pi and all is now well. You need an old tech power supply not any of the new digital sensing power supplies that are supplied with mobile phones, these are battery chargers, not power supplies. Just try an official Pi power supply and save yourself a lot of grief.
I had two PIs showing the identical problem on Octoprint.
One Pi was running more than a year with the identical hardware configuration before the last Octoprint update.
When I checked it with a powerful lab power supply set to 5.2V and connection directly to the GPIO pins and still get an undervoltage warning then the warning is stupid as there is no under voltage.
Now with the plugin disabled there is no problem. An "official" Pi Power supply cannot be better than a professional lab power supply.
I was working with one PI on my I3 Mega S for more than one year without any warning. Now with a newer OctoPI version (because of Phyton update) I do get warnings every time. Even with my lab supply directly connected to the GPIO pins. So don't tell me this is a problem of my power supply or cable.
Best regards
Onki
Maybe it's a problem with your PIs?
I've done the updates too and have any undervolatge issues.