I have an old charger from my RP3 using in RP4 with micro-usb -> usb-C cap on it. I have a feeling that my Pi has not enough power- When I start Pi with fan connected to pins, it makes sounds like it tries to speed up rotations of the fan but has not enough power for it. I tried to get voltage value of the pi's core And have this numbers is it normal?

>>> for id in core sdram_c sdram_i sdram_p ; do echo -e "$id:\t$(vcgencmd measure_volts $id)" ; done

core:   volt=0.8625V
sdram_c:    volt=1.1000V
sdram_i:    volt=1.1000V
sdram_p:    volt=1.1000V

// after connecting fan
>>>pi@raspberrypi:~ $ for id in core sdram_c sdram_i sdram_p ; do echo -e "$id:\t$(vcgencmd measure_volts $id)" ; done

core:   volt=0.8350V
sdram_c:    volt=1.1000V
sdram_i:    volt=1.1000V
sdram_p:    volt=1.1000V

BTW. It doesn't make that sound after RP is booted and warm-up

  • Core voltage is totally and utterly irrelevant. Do you have a Question?
    – Milliways
    Dec 11, 2020 at 7:32
  • How could I find if the voltage is sufficient? Dec 11, 2020 at 8:09
  • 1
    If the voltage is insufficient you would see the lightning bolt symbol on screen.
    – CoderMike
    Dec 11, 2020 at 9:00
  • 1
    @CoderMike: There is no "lightning bolt" for the "Lite" version of the OS, nor is there a lightning bolt for those running "headless" for any OS.
    – Seamus
    Jan 21, 2023 at 21:26

3 Answers 3


Is My Raspberry Pi Getting Enough Voltage?

Solution 1: Get an inline USB meter:

Rather than tilting at windmills, you could invest a few dollars to buy an inline USB meter. Simply read the voltage on the display - they also provide a current measurement which should be useful. For about $20USD you can avoid relying upon your "feelings" to measure voltage :) FWIW, I have used them, and mine work very well... yet - I can't shake the feeling that my feelings aren't quite as sharp since I began relying on instruments :)

inline USB meter

Solution 2: Watch the monitor connected to your RPi

If you run your RPi connected to a monitor, the under-voltage warning will be displayed in the upper right-hand corner of the monitor. It may flash intermittently, or it may remain on steadily.

Solution 3: Use the vcgencmd get_throttled command

You can use the vcgencmd utility from the command line (or use it in a script you write) to give you the status. This will work with or without a connected monitor. This requires a bit more effort than the first two solutions, but a potential advantage is that you may learn something. Using my RPi 3B+, it goes something like this:

$ vcgencmd get_throttled

What does that mean? In this case, throttled=0x50000 means that my RPi 3B+ has experienced an under-voltage event, and the CPU clock has been throttled. It also means that neither of those conditions exist at the time I ran this command. I'd also like to mention that my RPi 3B+ is powered from an "official" power supply, so under-voltage events will occur even when using a supply that meets RPi's specifications.

This, and other potentially useful information on vcgencmd is found here. Specifically, see the get_throttled option. Also see Note 1 below.

Review the table supplied in the online doc, read the explanation, and feel free to ask more questions - here, or in the discussion forums (e.g. 1, 2)


  1. Unfortunately, The Organization has elected not to provide much system documentation - there is no man page, and even vcgencmd --help isn't much help.

I found this: On all models of Raspberry Pi since the Raspberry Pi B+ (2014) except the Zero range, there is low-voltage detection circuitry that will detect if the supply voltage drops below 4.63V (+/- 5%). This will result in a warning icon being displayed on all attached displays and an entry being added to the kernel log.

It could also be your RAM. How many Gb RAM do you have?

I hope this helped


It sounds like you got a fan for the wrong voltage, or connected it to the wrong pins. Fans should be connected between 5V (or 3.3V) pins and ground, not to regular GPIOs. 5V is sufficient for most small fans, 3.3V is enough for some but might be insufficient for others.

If you connect a 12V fan to 5V, it is expected that it never reaches full speed.

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