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There is a lightning bolt icon flashing on the top right of my screen. What does it mean?

Here's a picture:

Screenshot of PIXEL lightning bolt symbol

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  • 28
    Severe weather alert. o_O <- Just a joke.
    – goldilocks ♦
    Commented Nov 22, 2016 at 0:57
  • 3
    OMG I snowed here, and is super ICY! Thanks Raspbian!
    – j0h
    Commented Nov 22, 2016 at 13:24
  • 1
    A 3 needs more power than a standard USB-port supplies.
    – Thorbjørn Ravn Andersen
    Commented Nov 28, 2016 at 17:46

4 Answers 4

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110

That's the new undervoltage symbol. Your Pi's power supply is marginal or insufficient for its requirements.

From the raspberrypi.org blog page:

Finally on the subject of icons, in the past if your Pi was working particularly hard, you might have noticed some yellow and red squares appearing in the top-right corner of the screen, which were indications of overtemperature or undervoltage. These have now been replaced with some new symbols that make it a bit more obvious what’s actually happening; there’s a lightning bolt for undervoltage, and a thermometer for overtemperature.

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29

The lightning bolt means that the Pi is not receiving the required voltage. This may be due to the power supply you are using or the cable (if separate). You should switch to a better supply/cable as undervolting can lead to SD card corruption and other difficult-to-trace issues.

You don't mention what model Pi you are using and what if anything you have plugged into the USB ports, but you may be able to get by with your existing power supply/cable if you use a powered USB hub to connect any USB device.

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    I got the lightning bolt with every power supply I had. Changed the USB cable to a different one and lightning bolt gone! I guess not all cables are created equal!
    – brad
    Commented Jan 27, 2018 at 11:57
  • @brad: did you have the official RPi supply or a smartphone charger of 5V and 2.4A?
    – Nav
    Commented Sep 29, 2020 at 21:11
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The lightning bolt means that you don't have enough power going to the Raspberry Pi.

Almost any standard micro USB cable will be able to power the Pi. Most of us have one or two laying around from getting them for our phones and we could easily use what we have to charge our phones to power the RPi.

However, the Raspberry Pi should have a 5 volt 2 amp USB power cable to sufficently power the the device (and not get the bolt).

Most Android/Smartphone/USB chargers though run on a 5 volt 1 amp charger, and some of the "fast chargers" are only 5 volt and less than 2 amp. These are big generalities and are constantly changing and do vary depending on how cheap you got it and where from and for what purpose.

Some of those "fast chargers" can go for up to $30, and will be a 5 volt 2 amp charger. However, you can get one from adafruit.com for just about $8, which is what a regular phone charger would cost elsewhere, see 5V 2.4A Switching Power Supply w/ 20AWG 6' MicroUSB Cable.

This amount of power, might be too much for your computing needs for the Pi. So a standard 5 volt 1 amp charger might be good enough until you decide what you are doing with it or just while you are learning and goofing with the OS and such.

I bought a 5 V 2.1 A from somewhere and it works great for my Pi, similar to the one from Adafruit.com. I forget where I got it though.

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    I highly doubt that 1V/1A and 2V/2A chargers are sold for phones.
    – Ghanima ♦
    Commented Nov 22, 2016 at 19:41
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    If you want some upvotes, you should edit your answer... Surely you mean 5V 1A, and 5V 2A?
    – Greenonline
    Commented Nov 26, 2016 at 11:52
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    Downvote due to "This amount of power, might be too much for your computing needs for the Pi". The device (e.g. RPi) draws the power it needs. Having a 1A PSU doesn't mean 1A flows all the time.
    – Aloha
    Commented Jun 19, 2019 at 5:29
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It also appears if you power the Pi from the GPIO power pins.

Everything works fine but the power led will not be lit.

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    Do you have a reference for this, or is it an inference? If the later, then perhaps what it really means is you are supplying insufficient voltage via the GPIO pins. Note that the lightning bolt and the PWR led being off are just warnings. They do not not necessarily indicate anything won't work, but it might be a clue if, e.g., you suddenly drew a lot of current via the USB jacks and the pi "mysteriously" rebooted.
    – goldilocks ♦
    Commented Nov 27, 2016 at 18:35
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    Will up vote if references are provided.
    – j0h
    Commented Nov 28, 2016 at 17:47
  • References? I, also, will upvote your answer - if you can ameliorate your answer, and provide (substantially) more information...
    – Greenonline
    Commented Dec 6, 2016 at 19:35
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    In my experience, powering the Pi via GPIO can lead to serious problems if the CPU is very busy and/or USB ports suck a lot of power. We had a case where the network interfaces continuously restarted making it impossible to reach the Pi via SSH.
    – henon
    Commented Oct 16, 2017 at 10:02
  • According to the schematic (pi v3) the +5V from the USB is attached to the +5V internal rail via a resettable fuse. So you can provide equivalent supply via the 5v header as long as you provide similar over current protection.
    – Tom
    Commented Mar 28, 2018 at 20:07

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