RPi - SD card draw voltage ?

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xpd

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#277214 2-Oct-2020 07:45

I have a Raspberry Pi 3B+ that I primarily use for RetroPie (gaming) on a 32GB SD card. Has been fine until last night......

I purchased a new 64GB SD card, installed RetroPie, connected controller, turned it on and got an under voltage warning. The only thing that changed was the SD card.

Is it possible the new card draws more power and has just tipped the voltages over ? :)

I'm going to buy a dedicated power adaptor anyway (any recommendations that I can obtain before October 14th ?) but just curious.

XPD / Gavin

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Behodar

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#2577685 2-Oct-2020 08:04

Interesting! How are you powering it now? I also have a 3B+ along with the official power supply and I have the Pi, SD card, SSD, a HAT, keyboard and mouse connected and haven't had any power warnings.

michaelmurfy

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#2577687 2-Oct-2020 08:07

Also check the USB cable you’re using. Low quality cables really suck with feeding the amps.

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xpd

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#2577688 2-Oct-2020 08:07

Always had it running off a 5V 2A USB charger (from my BT speaker) and never had that warning before :) I might try putting in the original SD card and see if it triggers again.

RetroPie still fired up after the warning, but didn't seem to want to power the Xbox controller afterwards.....

Like to get a replacement adaptor asap as Ive got a weekend away with mates and we were looking forward to some old school arcade gaming :D

XPD / Gavin

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Mehrts

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#2578271 2-Oct-2020 18:55

I kept getting low voltage warnings with all USB cables/chargers I tried when I first got my 3B+.

It was simply the fact that the 5V which was being output at the source wasn't 5V at the Pi due to wires which were too thin, therefore voltage drop over the cable was greater.

Bought a 5.1V USB power supply, and all is well. That extra 100mV was enough to prevent the low voltage warning from being triggered.

richms

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#2578366 2-Oct-2020 23:34

You can suppress the warning, its mainly of concern for USB devices that need the 5v to be 5v, it can sag heaps and the pi will keep working because its all way lower voltages. All my peripherals work fine with it low enough to warn, since they have 3.3v regulators on them anyway.

I have had better luck with my retropie cases which put power in via the GPIO pins vs using the micro USB on the board directly for not getting the warning even on the same USB cable and power brick, I think there is some protection on the USB input that causes some more drop to happen.

Richard rich.ms

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#2578378 2-Oct-2020 23:51

The RPi "needs" 5.1V.

https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.md

USB (2) specs can be 5.0V +0.25/-0.60.

https://en.wikipedia.org/wiki/USB

This mean you can have 100% valid USB power supply but the RPI complains if its below 4.63V

I've found with RPi's you need to really check your voltages or you can get some strange things