6A PSU on Raspberry Pi 3

weirdocollector

Hi!

Tired of getting continuous undervoltage warnings and to listen to the external USB drive clicks, I've just swapped a no-name 5V/3A PSU with a good brand 5A/6A that I connected to the PowerBlock I use to control my RasPi 3.

To my dismay, the situation is now worse as I still get the undervoltage warnings, the drive click continuously and the RasPi 3 is unable to read from it.

Why this happens ?

I was expecting that doubling the PSU juice would resolve all my problems.

There are some significant differences from an official PSU and a generic one that I'm not aware of ?

Thanks for any help.

dankcushions

@weirdocollector non-dedicated PSUs may not have stable supplies because other devices (eg mobile phones) don’t care like a pi does. also, throwing more amps at it doesn’t necessarily help - eg what’s the voltage ? it should be 5.1V for the 3

i have only had consistent good experience with the official raspberry pi PSUs.

weirdocollector

@dankcushions said in 6A PSU on Raspberry Pi 3:

@weirdocollector non-dedicated PSUs may not have stable supplies because other devices (eg mobile phones) don’t care like a pi does. also, throwing more amps at it doesn’t necessarily help - eg what’s the voltage ? it should be 5.1V for the 3

i have only had consistent good experience with the official raspberry pi PSUs.

I'm using a good quality PSU that outputs a stable 5.3V.
I'v now ordered a powered USB hub in order to connect the external drive.
I'm thinking about powering both the Pi and the hub due to the high amperage it can provide.

dankcushions

@weirdocollector yeah that should do it. else the usb drive can only pull power via the pi’s USB ports which are limited to 1200mA total (ie shared between all connected devices) if i recall.

lostless

@weirdocollector non-dedicated PSUs may not have stable supplies
I'm using a good quality PSU that outputs a stable 5.3V.
I'v now ordered a powered USB hub in order to connect the external drive.
I'm thinking about powering both the Pi and the hub due to the high amperage it can provide.

Never be sure that a power supply outputs a stable any voltage. unless you tested with a tester during use. Many USB power bricks are rated + or- 5% of actual voltage and can dip to the low end as you pull more amps. Also your cable can cause issues. If you aren't using a thick enough cable, voltage can drop even below the rated -5% by the time it reaches the pi. If you compare the cable thickness of the official raspberry pi cable to a run of the mill USB charging cable, it is thicker.
As @dankcushions said, our phones and devices are not sensitive to the drops, because when it drops, the battery just charges slower and less efficient.

weirdocollector

@lostless said in 6A PSU on Raspberry Pi 3:

@weirdocollector non-dedicated PSUs may not have stable supplies
I'm using a good quality PSU that outputs a stable 5.3V.
I'v now ordered a powered USB hub in order to connect the external drive.
I'm thinking about powering both the Pi and the hub due to the high amperage it can provide.

Never be sure that a power supply outputs a stable any voltage. unless you tested with a tester during use. Many USB power bricks are rated + or- 5% of actual voltage and can dip to the low end as you pull more amps. Also your cable can cause issues. If you aren't using a thick enough cable, voltage can drop even below the rated -5% by the time it reaches the pi. If you compare the cable thickness of the official raspberry pi cable to a run of the mill USB charging cable, it is thicker.
As @dankcushions said, our phones and devices are not sensitive to the drops, because when it drops, the battery just charges slower and less efficient.

I've measured 5.3V with my tester before connecting the PSU to the Pi.

I'll try with the USB hub to see what happens.

Thanks for your help!

lostless

@weirdocollector that’s the thing, 5.3v with no load. Plug a pi in with a usb hard drive and if it’s a standard usb charger that’s not regulated well, that will drop to lower voltages. Also if you use a standard usb charging cable, the cables are not very thick and act as a resistor (any cable does, just thickness and length change the effect) in higher currents. so while the power supply may be able to to give the right voltage, on the other end of the cable that plugs into the pi may be well below what the pi needs.

Lolonois

If you are sure the PSU can deliver 5.1V constantly or more (but not higher than 5.5V) under load then most likely the USB cable may be another source for the undervoltage. Search for "micro usb 24awg 2c". The AWG24 wire gauge allows up to two ampere. (cf. here). And pick the shortest you can get. It may fix the issue.

However, from theory this may still not enough for an RPI3 (rated 2.5A).
You may try this, but do it on your own risk: Power the Rpi3 via GPIO headers. This bypasses the voltage regulator of the microusb port, so only use a PSU which has a stabilized output. Caution: Any mistake in wiring will fry your Rpi.

Get or make two DuPont wires with female endings, either AWG24 or AWG22
Cut them apart, thus you have two for 5V and two for GND at the GPIO header
Properly attach the DuPont wires to the PSU, note the polarity
Attach the female endings to the respective GPIO headers (use 2x 5V and 2x Ground) (https://pinout.xyz/#), again note the polarity
Make sure the wires do not losen during gameplay