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I was using a raspberry power supply to power the pi in a setup for 3d printing, a camera and 5" lcd touchscreen run off the pi. I kept getting low voltage warnings so I purchased a 5v 5a power supply and wired it in, setting it's voltage output to 5.3v. I still kept getting low voltage warnings from the pi and the camera would shut off. I wound up turning the power supply output up to 5.7v and am no longer getting low power warnings but I don't want to be running the pi off a voltage that my burn it out. Can anyone tell me the maximum voltage I can supply the pi with? It seems stable at the 5.7v so I don't need to turn it up higher, just want to be sure that it isn't going to damage the pi to supply that much.

Mark Massingill
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  • what procedure are you using for measuring the 5.7 V? ... how is the connection made? – jsotola Jun 16 '21 at 22:35
  • The pi is connected via USB C cable that's plugged into a USB outlet soldered to wires from the power supply with a switch inline. Voltage has been measured at the power supply, at the USB port soldered in that the pi has been plugged into and at the USB C end with a multimeter. There has been no voltage drop in the wiring or USB cable, according to the digital multimeter I'm using. Voltage has been tested when pi was off, when pi was on, when pi was on with screen and camera in use with no drop in voltage. Switching power supply rated for 5v 5 amp (25w) output. – Mark Massingill Jun 17 '21 at 00:59
  • Can the camera or the LCD be powered from another source? – Seamus Jun 17 '21 at 04:24
  • OP said. "`There has been no voltage drop in the wiring or USB cable, according to the digital multimeter I'm using.`" I will guess that your measurement is in error unless you have: 1) an extremely short wiring run from PwrSupply to RPi USB-C connector, or 2) a custom-built USB-C cable using 12-14 AWG wiring. – Seamus Jun 17 '21 at 16:45
  • Yes, wiring is very short to USB port from power supply is 3" of 16awg and the USB C cable is 6", there is no noticeable voltage drop, if there is one it's in the thousandths of a volt and the inexpensive digital multimeter I'm using isn't picking up measurements that small. Again, my other pi4 has zero issues with either power supply under the same load at just 5.1v. – Mark Massingill Jun 17 '21 at 21:53
  • Does this answer your question? [Supply (under) voltage problem](https://raspberrypi.stackexchange.com/questions/118815/supply-under-voltage-problem) – Dmitry Grigoryev Jul 17 '21 at 11:24

2 Answers2

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"Power" is irrelevant; you should be looking at Voltage.

Almost certainly your power supply or the wiring is inadequate.

See Raspberry Pi Power Limitations

The Pi specification states power sources SHOULD provide 5±0.25V.
The MxL7704 PMIC Data states Input voltage range: 4.0V to 5.5V.

You risk blowing up your Pi, although most components will allow some parameters to be exceeded. I (as an experienced engineer) choose to follow specifications, unless there is a good reason.

Milliways
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  • Voltage is what I'm talking about, with the switching power supply at 5.1v I kept getting low voltage warnings, same at 5.3v, those stopped when I turned it up to 5.7v. The power supply is rated for 5v 5a (25w). Measured with a multimeter the voltage was constant, no drop at all. Pi was only drawing about 1.5amps and there was no drop in current either, yet any voltage below 5.5v I kept getting low voltage alerts and the camera would drop out, it would not reliably work until I turned up the supply voltage. I don't want to burn the pi out but I need it to work reliably. – Mark Massingill Jun 17 '21 at 01:16
  • If the voltage drops below 4.63±0.07V, even briefly, the indicator will be triggered. You can't see transients with a multimeter. Many (most) PSU have poor load regulation. – Milliways Jun 17 '21 at 01:57
  • Which is a possibility, yet even with the Raspberry power supply the same thing happened with the low voltage warnings and the camera dropping out. Hence the reason I asked what the maximum supplied voltage could safely be. Apparently I'll just have to do more research as no answer to the actual question seems to be forthcoming. Since the pi isn't overheating and seems to be doing fine at the current supplied voltage maybe I'll just leave it and see how long it lasts. – Mark Massingill Jun 17 '21 at 10:19
  • Au contraire. The answer to this question is simple - **5.5V** even though this is inadvisable and not recommended. – Milliways Jun 17 '21 at 10:23
  • 5.5v was the minimum it took to stop the problem occurring constantly, it would still occur randomly. 5.7 is what it took to make the low voltage warnings stop completely. Although yes, the answer should be quite simple as there is always leeway and there is a maximum safe voltage outside the 'recommended', there always is and I simply wanted to know if the 5.7v that Rpi4 seems to require to operate properly was within that margin. – Mark Massingill Jun 17 '21 at 11:00
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The issue with Switching Power Supply is: it TRIES to keep the voltage on the same level but as someone mentioned already - if you have a drop to 4.5V even for millisecond the Pi will detect it. I spent recently wast amount of time on RPi power supply as I was building UPS on supercaps and my findings are:

  • the best place to measure the voltage on Pi are the 5V pins and the ground - not the input of the USB port
  • 5.7V for RPi 4 is not an issue as long as it does not go even for microseconds above it - but I set up to have max 5.5V on PINs
  • when you have heavy load turning on, for the milliseconds you might have drop which ORDINARY voltmeter will not detect - oscilloscope could but it is a bit of overkill
  • I would suggest powering (if possible) external devices from external PS - not through RPi - separate power to RPi and camera but get another PS for i.e. USB devices
Zygfryd Homonto
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  • Even the official Raspberry power supply for the pi4 was giving the same problem with low voltage warnings so it's not just the switching supply. Thanks for the info, I'll check at the GPIO pins. As for powering devices elsewhere, both the camera and screen are powered via the ribbon cables from the pi, neither has separate power inputs. My other pi4 with the same peripherals works just fine off either power supply, no idea why the load is ok for it but not for this one. I'll just have to cross my fingers and hope for the best I guess. Thanks. – Mark Massingill Jun 17 '21 at 11:23
  • Official power supply from Raspberry is also switching power supply. I had issue with this one as well in few occasions: 1) when I added switch on/off - the voltage drop on the contacts, 2) when the plug/socket got lose (as RPi 4 does not have switch, you usually disconnect/connect the USB-C so it becomes lose) – Zygfryd Homonto Jun 18 '21 at 05:21