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That God %$#@ Lightning Bolt



  • @classicgmr You can ignore it, but lets see if you can ignore the throttling when you don't have insufficient power.



  • @classicgmr are you plugging directly into the wall?



  • @classicgmr also did you start with a stock 4.4 image or did up update from 4.3?



  • @ClassicGMR I actually just got a new "AUKRU" 5.25V 3A power supply from Amazon and I have to say I was impressed. Hefty plug and a very heavy cable. Just tried it the last few days with my 3B+. No issues at all.



  • @quicksilver Yes. Directly to the outlet. Also since it is a 3B I didn't even think of attempting an update. I imaged 4.4 freshly, shiny brand new from the site.

    @johnnykesh I will have to check that out. Actually now that you mention it I don't really think this is a great cable. I'll have to see if I have anything heavier.



  • @classicgmr A hardwired PSU is always going to be better than a plug plus USB cable.
    USB cables are just not designed to carry the Amps that a Pi needs. Go for an all in one.
    I got the power supply, plus loads of extra stuff I don't really need for a tenner, delivered the next day. Hard to argue with that.



  • @classicgmr https://www.amazon.com/Mackertop-HSTNN-LA43-PA-1150-22HA-779573-001-761247-002/dp/B01HB44IE6

    This is the power supply that I'm using with my pi3, I am also using the super kintaro case. I have had no issues with this power supply and I'm overclocked.



  • @jonnykesh said in That God %$#@ Lightning Bolt:

    USB cables are just not designed to carry the Amps that a Pi needs.

    Do you have a citation on this? I would think that the wire gauge of USB cables is more than enough to carry the amperage needed.



  • @markwkidd A citation? Really?
    Considering most USB chargers output no more than about 1.2A I would say that is pretty much a given. Why waste money on cables capable of more?
    You might get lucky and actually get one capable of delivering it. Certainly not in my experience.



  • @jonnykesh said in That God %$#@ Lightning Bolt:

    @markwkidd A citation? Really?
    Considering most USB charges output no more than about 1.2A I would say that is pretty much a given. Why waste money on cables capable of more?
    You might get lucky and actually get one capable of delivering it. Certainly not in my experience.

    Yes, when you are making electrical engineering claims that don't make sense, yes I'd like to know how you determined that USB cables can't carry the required amperage since you are advising others based on your determination.

    If you have never had one that could handle the amps, just say that.



  • @markwkidd I just did.
    I'm also making a recommendation based on best case scenario. Are you employed by "big USB" cable or something?
    Obviously you know that not all "wall warts" will output what they claim. They certainly won't if you team them up with a poor quality USB cable.
    I feel like I am being attacked for giving the best advice I can. As always advice is just that, my experience plus my knowledge of electronics. Take it or leave it. YMMV.



  • As an electrical engineer I would doubt whatever the pi is drawing is going to be an issue for the wire itself, but that doesn't mean the wire isn't the problem here either. Amperage plays into it, but it is not directly what this error is about. It's an undervoltage error. The wire doesn't have to be overheating and melting off it's insulation to be failing in this application. It could simply have just barely enough resistance, that with a healthy current draw from the pi, the voltage drop across it is enough to make the lightning bolt come up. Simple wall warts also see their voltage sag under load.

    What you should do is take a multimeter and measure the 5V where it's coming into the board. The connector 5V and ground are easily accessed from the bottom side of the board under the connector, but take care not to short anything to 5V. Try this under load and powered down. You should see a difference. If it is clear the voltage at the pi is too low you can only try a thicker and/or shorter cable that is less resistive, and if that doesn't do it then you're power supply just can't maintain the correct voltage under load.



  • @jonnykesh Not all usb cables are made equal. They can vary in awg. They are not "ideal", but they are usable if you get the lowest awg size you can find. The official pi ac adapter uses 18awg so I suppose you can get away with 20awg.



  • @quicksilver Looks like I may have to go with a hardwired 3A. I've had no luck with all these USB detachable chargers.

    The 2.5A PSU CanaKit (hardwired) gives me "Da Bolt" on occasion. I also have a 2.5A Viaboot hardwired that isn't any better.

    Will check out your PSU next time I put in an Amazon order. :)



  • @classicgmr I have tested that power supply while running cpuburn-a53 which is a test that runs the CPU at full speed. It's a great way to test your pi to see if your cooling and power needs are adequate. It passed without getting the low voltage warning, my 2.5amp canakit did not pass however.



  • @markwkidd said in That God %$#@ Lightning Bolt:

    Do you have a citation on this?

    This may help.



  • @rbaker said in That God %$#@ Lightning Bolt:

    @markwkidd said in That God %$#@ Lightning Bolt:

    Do you have a citation on this?

    This may help.

    Thanks! So we have manufacturers skimping on copper and violating the USB spec by reducing wire gauge.

    From what I'm reading there, it's still no reason to avoid one style of power supply over another. Just like controllers, cases, and anything else that's mass produced there are bogus cables out there. Source one from a reliable vendor or take chances with knockoff or out of spec gear.



  • @clippercm I agree! I'm also not a fan of the whole USB connectors used for power on the Pi's. In the USB 1.0 and 2.0 specs, a standard downstream port is capable of delivering up to 500mA (0.5A); with USB 3.0, it moves up to 900mA (0.9A). I wish they would have gone to a barrel power connector like most laptops use.


  • administrators

    @markwkidd yeah AliExpress is a terrible source for proper usb cables. My hub was proper but anytime the USB was plugged automatic lightning bolt.



  • If you have a couple multimeters (or a o-scope better yet) connect them to the output of the power source and look to see if the current is limited and tops out at a certain number or see if you get voltage drops when a load kicks in. I’m guessing cheap cables are the culprit, badly made cables made of cheap materials can act as an electrical shunt and cause unwanted resistance.



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