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Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Tue Jun 18, 2019 11:26 pm
by suak123
Hello,

I have got a cell phone charger and it is 5v 2a (it says).It's what I use to power my raspberry pi. But there is still a lightning bolt icon on the top right of my screen. It barely goes off. Should I be scared ?

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Tue Jun 18, 2019 11:35 pm
by HawaiianPi
Phone chargers are notorious for having poor voltage regulation, so they are not really suitable for use as power supplies. I had a 5V, 2.4A charger that dropped well below 5V at only a 1A load. It charged my phone and tablet fine (they only need a little over 4.2V to charge), but it was a lousy Pi power supply.

It also depends on what model Raspberry Pi, and what accessories you have attached to it. For example, the recommended power supply for the Pi 3B and 3B+ models is 5V and 2.5A, so a 2A PSU is less than recommended (okay for a Pi2 or less, but not for the Pi3).

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 12:15 am
by W. H. Heydt
suak123 wrote:
Tue Jun 18, 2019 11:26 pm
Hello,

I have got a cell phone charger and it is 5v 2a (it says).It's what I use to power my raspberry pi. But there is still a lightning bolt icon on the top right of my screen. It barely goes off. Should I be scared ?
Scared? No. It won't hurt the Pi. The biggest risk is some peripherals not working and the potential to corrupt the SD card. Best thing to do is to get the official RPF PSU...which you can use to charge a phone should you be a mind to when it's not powering a Pi. (In fact, I use older RPF PSUs--such as ones rated 2A--to charge phones, tablets, and the like.)

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 3:45 am
by LTolledo
Raspbian on your RPi (3B or 3B+) has been repeatedly informing you that the power is not enough (the "dreaded" lightning bolt icon).

probably something like this is happening....
RPi3B+: .....need more power .....please.... cant ...function...........properly

2.0A Phone charger: I can only give as much.... and my voltage is dropping already....

RPi3B+: ...not ..... enough...(cough...cough).... need ... more........

2.0A Phone charger: maybe you need help from a proper power supply with 2.5A.......

RPi3B+: ....take ...me .....(cough... cough) there .....[wheezes]...... now......!.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 2:46 pm
by PhilBr
I see messages like this so often!
Do you think we need a specific sticky 'phone chargers do not work'.
Not only will the voltage sag as load increases, but I fear won't some be regulated and will give over-voltage at times, with damaging consequences.
Phil

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 3:38 pm
by bensimmo
Does it use a separate 'usb' cable as the power wire? Or is is a proper all in one like the Official Pi PSU.
I would try better USB 'power/charge only' leads if you can find them. There are some rated for 2.5A delivery.
The cable and the uUSB connection itself create the largest voltage drop from my measurements of various cables.

Of course cables can be quite expensive, so often it is cheaper / easier just to get a 'good' power supply from the start.
E.g. the official one.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 3:41 pm
by B.Goode
PhilBr wrote:
Wed Jun 19, 2019 2:46 pm
I see messages like this so often!
Do you think we need a specific sticky 'phone chargers do not work'.
Not only will the voltage sag as load increases, but I fear won't some be regulated and will give over-voltage at times, with damaging consequences.
Phil

At least two problems with that.

Firstly, the bald statement you make is provably untrue, and publishing untrue information just discredits the rest of the advice available from the site.

And secondly, closely related information is already in TWO sticky posts on this forum: why would saying it a third time make any significant difference?

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 3:48 pm
by bensimmo
Agreed it is untrue, in front of me is an old black HUDL charger 5V/2.1A with a white removable USB cable that may or may not be from a HuaWei phone or Moto phone or...
Connected to a 3B+, with SenseHAT and USB -GNSS, Keyboard, Mouse
and I have no problems.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 9:06 pm
by Speedwell68
PhilBr wrote:
Wed Jun 19, 2019 2:46 pm
I see messages like this so often!
Do you think we need a specific sticky 'phone chargers do not work'.
Not only will the voltage sag as load increases, but I fear won't some be regulated and will give over-voltage at times, with damaging consequences.
Phil
That just isn't the case. I currently have two RPI 2Bs and two RPI Bs powered perfectly well using phone chargers. They are genuine LG and Samsung chargers rated at 2.4 amps using quality leads.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Wed Jun 19, 2019 10:34 pm
by LTolledo
RPis with the BCM2835 and BCM2836 SoC may be powered by some (not all) reputable phone charger as long as it's rated capacity complies with the board requirements.
The BCM2837 and BCM2837B0 ones are more power hungry, and phone chargers cannot keep up with the requirements of the board.

Remember, phone chargers were designed to charge 3.7v batteries, the supply voltage may drop to 4.2v and still be able to charge a 3.7v battery.
None of those phone chargers were designed with the power requirements of the RPi3B or RPi3B+ in mind.

If you cannot follow the logic in this then its up to you.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 2:51 pm
by bensimmo
LTolledo wrote:
Wed Jun 19, 2019 10:34 pm
RPis with the BCM2835 and BCM2836 SoC may be powered by some (not all) reputable phone charger as long as it's rated capacity complies with the board requirements.
The BCM2837 and BCM2837B0 ones are more power hungry, and phone chargers cannot keep up with the requirements of the board.

Remember, phone chargers were designed to charge 3.7v batteries, the supply voltage may drop to 4.2v and still be able to charge a 3.7v battery.
None of those phone chargers were designed with the power requirements of the RPi3B or RPi3B+ in mind.

If you cannot follow the logic in this then its up to you.
Chargers have moved along since the old days of 0.5A or even 1A chargers, the demands are much greater now for fast charging and quality.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 4:34 pm
by davidcoton
There are three categories of charger:
  1. The Good
  2. The Bad
  3. The Ugly
Only chargers in the first category will work properly to power a Pi.
Unfortunately it is not always possible to determine the category of a particular charger;
some may even vary in category depending on temperature, phase of moon, and how badly you need it to work.

:o :shock: :? :twisted: :roll: :( :cry:

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 5:10 pm
by gordon77
davidcoton wrote:
Thu Jun 20, 2019 4:34 pm
There are three categories of charger:
  1. The Good
  2. The Bad
  3. The Ugly
Only chargers in the first category will work properly to power a Pi.
Unfortunately it is not always possible to determine the category of a particular charger;
some may even vary in category depending on temperature, phase of moon, and how badly you need it to work.

:o :shock: :? :twisted: :roll: :( :cry:
Which models fall into 'ugly'? ;)

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 5:24 pm
by hippy
PhilBr wrote:
Wed Jun 19, 2019 2:46 pm
Do you think we need a specific sticky 'phone chargers do not work'.
No. It needs to be far more nuanced than. I am using a cheap 500mA phone charger with an equally cheap USB cable and that powers my Pi well, no signs of under voltage at all.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 5:24 pm
by DougieLawson
gordon77 wrote:
Thu Jun 20, 2019 5:10 pm
Which models fall into 'ugly'? ;)
I have a very pretty Ikea Koppla 3-port phone charger, but when it comes to powering a RPi it's decidedly ugly.

https://www.ikea.com/gb/en/products/sma ... -40415031/

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 5:34 pm
by Andyroo
DougieLawson wrote:
Thu Jun 20, 2019 5:24 pm
...
I have a very pretty Ikea Koppla 3-port phone charger, but when it comes to powering a RPi it's decidedly ugly.
...
I have one powering two zero Ws fine but would not try three :lol:

Both have 3m leads but they are close to 4mm in diameter - best £3.50 I've spent on cables

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 6:02 pm
by Moonmarch
The official RPI power supply has a button that shuts off power to the RPI, instead of needing to unplug and plug the power supply into the power outlet to use the RPI every time, push the button instead which I would say is more convenient, the cell phone chargers I assume do not have this feature, modern day cell phones use the USB to USB-C connector, the RPI uses the micro USB connector.

A 5V Power supply is not expensive, more amps will be more expensive, there is no real need for a power supply greater than 5V2.5A unless you overclock the RPI, you don't need to spend $25 on a new power supply actually the price should be around $10.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 6:24 pm
by jahboater
Here is the spec of the "official" Raspberry Pi PSU. Its known to work reliably for all Pi models.

https://docs-emea.rs-online.com/webdocs ... 4ba6b1.pdf

https://uk.rs-online.com/web/p/products ... lsrc=aw.ds

At £6.50 ex vat, its also dead cheap. Why bother trying to re-use a phone charger?

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 6:25 pm
by wildfire
Moonmarch wrote:
Thu Jun 20, 2019 6:02 pm
The official RPI power supply has a button that shuts off power to the RPI
News to me, all my Pi's are powered by the Official supply. It could be new, country related or a feature of the enclosure of your Pi (One of my cases does have a power on/reboot/off switch but it's not official).

A link to this supply would be appreciated.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Thu Jun 20, 2019 6:39 pm
by HawaiianPi
Moonmarch wrote:
Thu Jun 20, 2019 6:02 pm
The official RPI power supply has a button that shuts off power to the RPI...
No it does not. Whatever you have, it's definitely not official. And power switched on the low voltage side is not good practice, so that's not a particularly good power supply design (better to switch the high voltage).

If the seller told you that was an official Raspberry Pi Foundation power supply, they lied.

Re: Is my cell phone charger good enough to supply power to my raspberry pi

Posted: Fri Jun 21, 2019 8:01 am
by Moonmarch
Okay fine if you guessed that I didn't check to see if there was a button on the official RPI power supply you are 100% correct, I was in a hurry, I was actually referring to the RPI starter kit that I purchased for sale on Amazon, here is a link to the product page:

https://www.amazon.com/CanaKit-Raspberr ... JJCAFW2S6J

You can purchase either the Canakit RPI starter kit or the Vilros RPI starter kit and these starter kits contain all of the accessories you would need for the RPI computers, here is a link to the Vilros starter kit:

https://www.amazon.com/V-Kits-Raspberry ... 7690997011

I don't actually use the Canakit power supply anymore, I use a 5V3A power supply.