Raspberry Pi Forums

I know this question was asked several times but it is something critical and can make me destroy whole RPI which it costs much at my place and I tried to find the official RPI PSU but unfortunately its not available in my country and my current one not supplying enough current. The charger i have is samsung note 4 Fast charger with output 9v dotted line then line 1.67amps or 5v dotted line then line 2amps looks like this one but with type C socket:

so Is it safe to plug it in RPI3 B+ and left on for really long periods?


Thanks alot

While that device *might* successfully power a Pi3B+, it is actually below the power specification for the Pi3B+: 2.5A @ 5v. If you let us know what country you're in, people might be able to point to a source for the official RPF PSU accessible to you.

AGID wrote: ↑

Mon Mar 30, 2020 5:39 pm

I know this question was asked several times but it is something critical and can make me destroy whole RPI which it costs much at my place and I tried to find the official RPI PSU but unfortunately its not available in my country and my current one not supplying enough current. The charger i have is samsung note 4 Fast charger with output 9v dotted line then line 1.67amps or 5v dotted line then line 2amps looks like this one but with type C socket:

so Is it safe to plug it in RPI3 B+ and left on for really long periods?


Thanks alot

The Raspberry Pi has nothing to charge, therefore it needs a Power Supply.


The official Power Supply is 5.1V 2.5A:

https://www.raspberrypi.org/documentati ... /#pi-power

W. H. Heydt wrote: ↑

Mon Mar 30, 2020 5:43 pm

While that device *might* successfully power a Pi3B+, it is actually below the power specification for the Pi3B+: 2.5A @ 5v. If you let us know what country you're in, people might be able to point to a source for the official RPF PSU accessible to you.

egypt and i have searched alot with no success.

fruitoftheloom wrote:

AGID wrote: ↑

Mon Mar 30, 2020 5:39 pm

I know this question was asked several times but it is something critical and can make me destroy whole RPI which it costs much at my place and I tried to find the official RPI PSU but unfortunately its not available in my country and my current one not supplying enough current. The charger i have is samsung note 4 Fast charger with output 9v dotted line then line 1.67amps or 5v dotted line then line 2amps looks like this one but with type C socket:

so Is it safe to plug it in RPI3 B+ and left on for really long periods?


Thanks alot

The Raspberry Pi has nothing to charge, therefore it needs a Power Supply.


The official Power Supply is 5.1V 2.5A:

https://www.raspberrypi.org/documentati ... /#pi-power

I really have no other choice atm. and i saw some engineer on forum says this was tested and he has graph for the result but i dont understand it. here:

http://www.cpmspectrepi.uk/raspberry_pi ... EP-TA20UWE

The Pi3 B+ by itself should run fine on that power supply. The 2.5 A recommendation allows for the Pi plus accessories so it will depend upon your configuration whether a 2.0 A supply is sufficient. USB flash sticks in particular can draw relatively large currents. There's also a concern as to whether a random power supply can actually achieve it's advertised performance, but a name brand OEM device probably does.

In any case you are very unlikely to damage the RPi by trying it with this supply. If this supply isn't sufficient you will see the low voltage warning and there is some chance that the SD card may be corrupted or damaged.

Keep in mind that the USB power cord performance is also important, so you want a good quality cable, preferably a shorter one.

That graph (http://www.cpmspectrepi.uk/raspberry_pi ... EP-TA20UWE ) is really quite poor performance and well short of spec - it dips below 4.8V at about 0.55A (though it does strangely bounce back). The official PSU I tested didn't dip below 4.8V until above 3A (http://www.astounding.org.uk/ian/raspi- ... _test.html top graph).

I'm quite surprised Smasung does that badly - I have a samsung USB supply that does much better than that.

However, all the testing on that page only goes up to about 0.75A (one or two go a little higher). That's still well below spec for a Pi with peripherals attached, so that testing doesn't really help much.

The problem with chargers is that charging batteries does not require precise voltage regulation, and because of that chargers often have poor regulation that will not maintain a stable 5V under load. I used to have a "5V/2.4A" charger that dipped well below 5V at only a 1A load. That's not to say all chargers are crap, some work very well as power supplies, but you'll never know without a proper load test (and most users don't own an adjustable current load tester).

When the charger requires a separate USB cable the problems can be compounded by too much resistance in the cable. Most USB 2.0 micro USB cables are not designed to deliver much more than 500mA (0.5A) without voltage loss, so you not only need a good charger, you need a good USB cable designed for charging high-end smartphones and tablets. Then length of the cable can also affect voltage (shorter is better).

Combine a standard micro USB 2.0 cable with a dodgy charger and you will not be able to reliably power a Raspberry Pi 3B(+) computer.

The 5V/2.5A recommendation for the Pi 3B(+) computers is based on 1.2A for the USB ports and accessories, and 1.3A for the SoC and system board. So a 2A PSU could work, assuming you have nothing else attached drawing significant power (you only have about 700mA of headroom, assuming your 2A supply rating is accurate). A power hungry USB device or HAT will require a more powerful PSU.

So, you could try different micro USB cables to see if you have one that works better. If you have a charging cable from an old smartphone or tablet, that might help.

AGID wrote: ↑

Mon Mar 30, 2020 6:10 pm

W. H. Heydt wrote: ↑

Mon Mar 30, 2020 5:43 pm

While that device *might* successfully power a Pi3B+, it is actually below the power specification for the Pi3B+: 2.5A @ 5v. If you let us know what country you're in, people might be able to point to a source for the official RPF PSU accessible to you.

egypt and i have searched alot with no success.

fruitoftheloom wrote:

AGID wrote: ↑

Mon Mar 30, 2020 5:39 pm

I know this question was asked several times but it is something critical and can make me destroy whole RPI which it costs much at my place and I tried to find the official RPI PSU but unfortunately its not available in my country and my current one not supplying enough current. The charger i have is samsung note 4 Fast charger with output 9v dotted line then line 1.67amps or 5v dotted line then line 2amps looks like this one but with type C socket:

so Is it safe to plug it in RPI3 B+ and left on for really long periods?


Thanks alot

The Raspberry Pi has nothing to charge, therefore it needs a Power Supply.


The official Power Supply is 5.1V 2.5A:

https://www.raspberrypi.org/documentati ... /#pi-power

I really have no other choice atm. and i saw some engineer on forum says this was tested and he has graph for the result but i dont understand it. here:

http://www.cpmspectrepi.uk/raspberry_pi ... EP-TA20UWE

I think you are referring to a Moderator, @FTrevorGowen. https://www.raspberrypi.org/forums/memb ... le&u=60180



He may have been an engineer in his professional life, but I don't think he claims to be a Raspberry Pi Engineer at the present time.

Aside from that charger, what other possible power sources or power converters do you have in your possession?

B.Goode wrote: ↑

Mon Mar 30, 2020 8:11 pm

AGID wrote: ↑

Mon Mar 30, 2020 6:10 pm

W. H. Heydt wrote: ↑

Mon Mar 30, 2020 5:43 pm

While that device *might* successfully power a Pi3B+, it is actually below the power specification for the Pi3B+: 2.5A @ 5v. If you let us know what country you're in, people might be able to point to a source for the official RPF PSU accessible to you.

egypt and i have searched alot with no success.

fruitoftheloom wrote:


The Raspberry Pi has nothing to charge, therefore it needs a Power Supply.


The official Power Supply is 5.1V 2.5A:

https://www.raspberrypi.org/documentati ... /#pi-power

I really have no other choice atm. and i saw some engineer on forum says this was tested and he has graph for the result but i dont understand it. here:

http://www.cpmspectrepi.uk/raspberry_pi ... EP-TA20UWE

I think you are referring to a Moderator, @FTrevorGowen. https://www.raspberrypi.org/forums/memb ... le&u=60180



He may have been an engineer in his professional life, but I don't think he claims to be a Raspberry Pi Engineer at the present time.

Yes, Sorry. I guess i have mis-read the badge.

LTolledo wrote: ↑

Mon Mar 30, 2020 8:55 pm

Aside from that charger, what other possible power sources or power converters do you have in your possession?

arduino one but with low current and another charger with 2xports with total of 2.6amps. btw i have used the charger it works but the temp was 50C with the lower amp charger and now it raised to 59-60C is that from the new 2Amp charger? it's good to mention that weather got bit hotter than yesterday. also the red led in raspberry is turning on for longer periods than with other charger

B.Goode wrote: ↑

Mon Mar 30, 2020 8:11 pm

AGID wrote: ↑

Mon Mar 30, 2020 6:10 pm

W. H. Heydt wrote: ↑

Mon Mar 30, 2020 5:43 pm

While that device *might* successfully power a Pi3B+, it is actually below the power specification for the Pi3B+: 2.5A @ 5v. If you let us know what country you're in, people might be able to point to a source for the official RPF PSU accessible to you.

egypt and i have searched alot with no success.

fruitoftheloom wrote:
The Raspberry Pi has nothing to charge, therefore it needs a Power Supply.

The official Power Supply is 5.1V 2.5A:
https://www.raspberrypi.org/documentati ... /#pi-power

I really have no other choice atm. and i saw some engineer on forum says this was tested and he has graph for the result but i dont understand it. here:

http://www.cpmspectrepi.uk/raspberry_pi ... EP-TA20UWE

I think you are referring to a Moderator, @FTrevorGowen. https://www.raspberrypi.org/forums/memb ... le&u=60180

He may have been an engineer in his professional life, but I don't think he claims to be a Raspberry Pi Engineer at the present time.

Before I retired (just before the first Pi's release) I worked for ~35yrs in R&D. In my younger days that involved designing and building dedicated experimental opto-electronic instrumentation for both lab. and field trials. Later on my work became more & more software based associated with the modelling of infra-red radiation from objects of interest. I was pointed in the direction of the RPF and the Pi by a younger, Comp. Sci. colleague as a possible post-retirement "project" and, although I was "watching closely" was not quick enough to get one out of the first batch and had to wait a while. Whilst waiting, given that I (and the family) had a few 'phone chargers lying around I began to assess them for "usability" largely prompted by issues, including safety, with some Apple iphone clones reported in the blog at that time.
Labelling of 'phone chargers and USB power supplies can be misleading. In general a charger may be able to supply 5V and 2A (for example) but not at the "same time" - with a 2A load the voltage will fall and not just due to lead/cable resistance. A USB power supply (for a hub) should suffer from less voltage drop at it's labelled (not specified) maximum current (with a short cable). Some devices, for safety reasons, may also have "current-limiting circuitry" where, beyond a threshold, the voltage falls rapidly: https://www.cpmspectrepi.uk/raspberry_p ... ger_10A15A

Trev.

FTrevorGowen wrote: ↑

Mon Mar 30, 2020 9:36 pm

B.Goode wrote: ↑

Mon Mar 30, 2020 8:11 pm

AGID wrote: ↑

Mon Mar 30, 2020 6:10 pm

egypt and i have searched alot with no success.



I really have no other choice atm. and i saw some engineer on forum says this was tested and he has graph for the result but i dont understand it. here:

http://www.cpmspectrepi.uk/raspberry_pi ... EP-TA20UWE

I think you are referring to a Moderator, @FTrevorGowen. https://www.raspberrypi.org/forums/memb ... le&u=60180

He may have been an engineer in his professional life, but I don't think he claims to be a Raspberry Pi Engineer at the present time.

Before I retired (just before the first Pi's release) I worked for ~35yrs in R&D. In my younger days that involved designing and building dedicated experimental opto-electronic instrumentation for both lab. and field trials. Later on my work became more & more software based associated with the modelling of infra-red radiation from objects of interest. I was pointed in the direction of the RPF and the Pi by a younger, Comp. Sci. colleague as a possible post-retirement "project" and, although I was "watching closely" was not quick enough to get one out of the first batch and had to wait a while. Whilst waiting, given that I (and the family) had a few 'phone chargers lying around I began to assess them for "usability" largely prompted by issues, including safety, with some Apple iphone clones reported in the blog at that time.
Labelling of 'phone chargers and USB power supplies can be misleading. In general a charger may be able to supply 5V and 2A (for example) but not at the "same time" - with a 2A load the voltage will fall and not just due to lead/cable resistance. A USB power supply (for a hub) should suffer from less voltage drop at it's labelled (not specified) maximum current (with a short cable). Some devices, for safety reasons, may also have "current-limiting circuitry" where, beyond a threshold, the voltage falls rapidly: https://www.cpmspectrepi.uk/raspberry_p ... ger_10A15A

Trev.

Thanks alot for clarifying, Trev.

You mention a type C usb socket... The Pi3b+ uses micro usb b

On this https://www.raspberrypi.org/products/ra ... er-supply/ page for the PSU for the Pi3B+, I don't see Egypt listed in the pull-down list of countries to look for vendors, but there are several at the bottom that I can't read because they don't use the Latin alphabet. You might look there.

(Some I can eliminate, such as the ones in Greek, Cyrillic and Hebrew.)

Imperf3kt wrote: ↑

Tue Mar 31, 2020 2:40 am

You mention a type C usb socket... The Pi3b+ uses micro usb b

I meant the plug itself not the cable.

W. H. Heydt wrote: On this https://www.raspberrypi.org/products/ra ... er-supply/ page for the PSU for the Pi3B+, I don't see Egypt listed in the pull-down list of countries to look for vendors, but there are several at the bottom that I can't read because they don't use the Latin alphabet. You might look there.

(Some I can eliminate, such as the ones in Greek, Cyrillic and Hebrew.)

Unfortunately, nothing for Egypt there.

AGID wrote: ↑

Tue Mar 31, 2020 10:11 pm

Imperf3kt wrote: ↑

Tue Mar 31, 2020 2:40 am

You mention a type C usb socket... The Pi3b+ uses micro usb b

I meant the plug itself not the cable.

W. H. Heydt wrote: On this https://www.raspberrypi.org/products/ra ... er-supply/ page for the PSU for the Pi3B+, I don't see Egypt listed in the pull-down list of countries to look for vendors, but there are several at the bottom that I can't read because they don't use the Latin alphabet. You might look there.

(Some I can eliminate, such as the ones in Greek, Cyrillic and Hebrew.)

Unfortunately, nothing for Egypt there.

On one hand, the tests indicate that the voltage is not dangerously high. On the other hand, the voltage does seem to dip rather badly. In my opinion, one of the main upgrades when moving to the 3B+ model was smarter voltage regulation.

On the 3B+ you can reduce current by running the network at 100mbit (connect to a 100mbit only switch) and by under clocking the CPU to 1000 MHz or less so the power consumption doesn't spike under load. Even after applying these measures, it is not clear the Pi will work correctly with your power supply and it is wise to proceeded with caution.