compnaion
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Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:16 pm

I was using the pi via viewer so far, then I wanted to connect it to a screen. I connected the hdmi, a small keyboard with no backlighting whatsoever, and a wireless mouse. About 2m later- when I opened browser to youtune, it started the yellow lightningbolt signal. It is said in power requirements 2.5 is enough, and surely nothing is taking 2A to work on raspberry pi, since most keyboards are 0.1W, so why the signal? And no heating on pi either, attached a fan to it.

drgeoff
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:23 pm

What PSU are you using? Many do not live up to what is on the label. And if using a separate USB to micro-USB cable that could be dropping voltage if too long or too thin or having wet string inside instead of real copper.

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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:26 pm

Is the fan plugged into the Pi or share the power supply output?
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:27 pm

compnaion wrote:
Tue Apr 09, 2019 1:16 pm
I was using the pi via viewer so far, then I wanted to connect it to a screen. I connected the hdmi, a small keyboard with no backlighting whatsoever, and a wireless mouse. About 2m later- when I opened browser to youtune, it started the yellow lightningbolt signal. It is said in power requirements 2.5 is enough, and surely nothing is taking 2A to work on raspberry pi, since most keyboards are 0.1W, so why the signal? And no heating on pi either, attached a fan to it.

Here is the ONLY answer:

https://www.raspberrypi.org/products/ra ... er-supply/


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

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compnaion
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:38 pm

drgeoff wrote:
Tue Apr 09, 2019 1:23 pm
What PSU are you using? Many do not live up to what is on the label. And if using a separate USB to micro-USB cable that could be dropping voltage if too long or too thin or having wet string inside instead of real copper.
It's a phone charger, for fast charging. Not too cheap, not really expensive either

compnaion
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:39 pm

Andyroo wrote:
Tue Apr 09, 2019 1:26 pm
Is the fan plugged into the Pi or share the power supply output?
It is plugged into the pi

compnaion
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:42 pm

fruitoftheloom wrote:
Tue Apr 09, 2019 1:27 pm
compnaion wrote:
Tue Apr 09, 2019 1:16 pm
I was using the pi via viewer so far, then I wanted to connect it to a screen. I connected the hdmi, a small keyboard with no backlighting whatsoever, and a wireless mouse. About 2m later- when I opened browser to youtune, it started the yellow lightningbolt signal. It is said in power requirements 2.5 is enough, and surely nothing is taking 2A to work on raspberry pi, since most keyboards are 0.1W, so why the signal? And no heating on pi either, attached a fan to it.

Here is the ONLY answer:

https://www.raspberrypi.org/products/ra ... er-supply/


https://www.raspberrypi.org/documentati ... /#pi-power
That charger is too expensive it is like buying a 300$ charger for a phone that has a price of 1000$.

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NGC6543
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:47 pm

It amazes me how many times this question comes up here since I joined a few weeks ago.

But then, the first thing I tried to use was a proper, branded 2.5A phone charger. Low voltage warning instantly, :lol:

Phone chargers are not power supplies - at best they have poorly regulated, approximate voltage outputs that drop lower as soon as significant current is drawn. They are simply not designed to give a regulated 5V output across their current range because that costs a few extra pennies, and isn't needed for charging phones. Even the cables and connectors aren't designed to have minimal drop. Everything is as cheap as it can be made, which is fine for a phone but not for proper electronics that needs regulated 5V.

Many of them even have choppy, AC-superimposed outputs which again a phone won't notice, but the Pi sure will.

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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:52 pm

compnaion wrote:
Tue Apr 09, 2019 1:42 pm
That charger is too expensive it is like buying a 300$ charger for a phone that has a price of 1000$.
That charger is not a charger, it is a regulated power supply.

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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 1:53 pm

compnaion wrote:
Tue Apr 09, 2019 1:38 pm
drgeoff wrote:
Tue Apr 09, 2019 1:23 pm
What PSU are you using? Many do not live up to what is on the label. And if using a separate USB to micro-USB cable that could be dropping voltage if too long or too thin or having wet string inside instead of real copper.
It's a phone charger, for fast charging. Not too cheap, not really expensive either

A Phone Charger and Power Supply are not the same as they are designed for different purposes.

:shock:
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compnaion
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 2:26 pm

NGC6543 wrote:
Tue Apr 09, 2019 1:47 pm
It amazes me how many times this question comes up here since I joined a few weeks ago.

But then, the first thing I tried to use was a proper, branded 2.5A phone charger. Low voltage warning instantly, :lol:

Phone chargers are not power supplies - at best they have poorly regulated, approximate voltage outputs that drop lower as soon as significant current is drawn. They are simply not designed to give a regulated 5V output across their current range because that costs a few extra pennies, and isn't needed for charging phones. Even the cables and connectors aren't designed to have minimal drop. Everything is as cheap as it can be made, which is fine for a phone but not for proper electronics that needs regulated 5V.

Many of them even have choppy, AC-superimposed outputs which again a phone won't notice, but the Pi sure will.
I see, it's annoying but makes sense. Thank you for the answer.

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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 2:54 pm

I have used a Motorola fast phone charge on a Pi with no problem, so it really depends on the quality of the charger and the cable. But as others have said, the best option is to buy a dedicated power supply.
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 7:03 pm

jamesh wrote:
Tue Apr 09, 2019 2:54 pm
I have used a Motorola fast phone charge on a Pi with no problem, so it really depends on the quality of the charger and the cable. But as others have said, the best option is to buy a dedicated power supply.

before I add my comment, I fully support the recommendation to use the official raspberry pi power supply.

Just because I can I did a small test using a few chargers I got here to power a Pi3B (not +) with a wireless USB keyboard and a wireless USB mouse attached. For all tests I used a short (80cm) Samsung cable that was included with a Samsung smartphone.

The following chargers were used (red means failed):
Sony 5V 850mA
Beco 5V 1A "designed by Apple in California" :D
Asus 5V 2A (from Asus Memopad 10FHD)
Samsung Travel Adapter 5V 1A (from Galaxy J4+)
Samsung Travel Adapter 5V 2A (9V 1.67A, from Galaxy Tab S4)
Samsung Travel Adapter 5V 2A (12V 1.25A, 9V 1.67A)
allocacoc Power Bar 5V 2.1A https://www.amazon.co.uk/allocacoc-Adap ... B00RBR5NGG
(not tested another Asus charger because it is currently powering my Pi0W fail2ban ssh gateway)

My finding is that a charger from a well known company with a rating of at least 2A can be capable to power a slightly loaded Raspberry Pi 3B. From experience I do not expect that these chargers will be able to reliably power a Raspberry Pi 3B+ or a Pi 3B with wired keyboard/mouse and/or HDD attached. If anybody is willing to donate a Pi 3B+ I can do some more testing.
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 7:30 pm

Ernst wrote:
Tue Apr 09, 2019 7:03 pm
jamesh wrote:
Tue Apr 09, 2019 2:54 pm
I have used a Motorola fast phone charge on a Pi with no problem, so it really depends on the quality of the charger and the cable. But as others have said, the best option is to buy a dedicated power supply.
before I add my comment, I fully support the recommendation to use the official raspberry pi power supply.

Just because I can I did a small test using a few chargers I got here to power a Pi3B (not +) with a wireless USB keyboard and a wireless USB mouse attached. For all tests I used a short (80cm) Samsung cable that was included with a Samsung smartphone.

The following chargers were used (red means failed):
Sony 5V 850mA
Beco 5V 1A "designed by Apple in California" :D
Asus 5V 2A (from Asus Memopad 10FHD)
Samsung Travel Adapter 5V 1A (from Galaxy J4+)
Samsung Travel Adapter 5V 2A (9V 1.67A, from Galaxy Tab S4)
Samsung Travel Adapter 5V 2A (12V 1.25A, 9V 1.67A)
allocacoc Power Bar 5V 2.1A https://www.amazon.co.uk/allocacoc-Adap ... B00RBR5NGG
(not tested another Asus charger because it is currently powering my Pi0W fail2ban ssh gateway)

My finding is that a charger from a well known company with a rating of at least 2A can be capable to power a slightly loaded Raspberry Pi 3B. From experience I do not expect that these chargers will be able to reliably power a Raspberry Pi 3B+ or a Pi 3B with wired keyboard/mouse and/or HDD attached. If anybody is willing to donate a Pi 3B+ I can do some more testing.
FWIW, you may be interested in the testing/measurements of various USB power supplies & chargers I've logged since the first Pi:
http://www.cpmspectrepi.uk/raspberry_pi ... plies.html
http://www.cpmspectrepi.uk/raspberry_pi ... dPSUs.html
http://www.cpmspectrepi.uk/raspberry_pi ... 2FChargers
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 8:04 pm

Thought I'd throw this in the mix:

http://www.righto.com/2012/10/a-dozen-u ... le-is.html

The power curve captures demonstrate why cheap chargers aren't good enough.

Also why you should avoid them altogether, even if they work well enough for your phone: http://www.righto.com/2012/03/inside-ch ... y-you.html

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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 8:34 pm

compnaion wrote:
Tue Apr 09, 2019 1:42 pm
That charger is too expensive it is like buying a 300$ charger for a phone that has a price of 1000$.
Define too expensive?

I have 2 of the official power supplies, and they only cost me $8.99 each. That's cheaper than most phone chargers I own.

The difference between 5V/2.4A and 5V/2.5A is half a watt (12.5 vs 12 watts). Assuming your charger has stable voltage regulation (see below), and you have a good, low resistance micro USB cable delivering the power, that half a watt is negligible under all but the most extreme loads.

It breaks down like this. The SoC can draw up to 1.3A under full load, and the USB ports are spec'd to deliver up to 1.2A (all 4 ports combined, with no per-port limits). So in theory, a headless 3B+ with nothing else attached could run from a good 1.5A power supply (but I would not recommend it). This is why some people get away with using 2A power supplies (which have roughly 700mA of headroom). 2A will work until you connect a power hungry USB device or HAT, and then the trouble starts.
jamesh wrote:
Tue Apr 09, 2019 2:54 pm
I have used a Motorola fast phone charge on a Pi with no problem, so it really depends on the quality of the charger and the cable. But as others have said, the best option is to buy a dedicated power supply.
Yup, you not only need a good charger, but also a good power cable. Standard micro USB 2.0 cables aren't designed to deliver much more than 500mA without voltage loss. So you not only need a charger with good regulation, you also need a micro USB cable that can deliver the current needed by the Raspberry Pi (which can be up to 2.5A for a 3B+ model with a heavy software load and power hungry accessories). Cables included with tablets and smartphones are usually rated for higher curren (there are fast charge cables rated for up to 2.4A).

Also note that longer cables have more resistance, so you want to avoid long micro USB cables. If you need to power a Pi that's not near an outlet, use an extension cord to move the PSU closer (or find an alternate solution, such as POE).

So, yes, phone chargers *might* work. The problem is, you can never be sure unless you properly load test the charger, and most people don't have a constant current load tester. This is why they are not recommended. I myself have a couple of RAVPower chargers that work great , but they cost me double the price of the official PSU. I suppose that depends on wherre you live and who you buy from, but in my case the official PSU is the least expensive solution that works.
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 9:09 pm

compnaion wrote:
Tue Apr 09, 2019 1:42 pm

That charger is too expensive it is like buying a 300$ charger for a phone that has a price of 1000$.
to some, a $9.00 RPF-PSU (and the peace of mind it provides) is more expensive than agony, hair-pulling frustration, wasted time and effort (and potential damage to $35 RPi3B+ and say $15 A1 microSD card) compared to using using a readily available charger
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Re: Is 2.4A 5V not enough for pi 3 b+?

Tue Apr 09, 2019 9:57 pm

compnaion wrote:
Tue Apr 09, 2019 1:42 pm
That charger is too expensive it is like buying a 300$ charger for a phone that has a price of 1000$.
That's a ridiculous analogy. $300 would be a financial burden for many, while most of those same people wouldn't think twice about spending $9 on a good lunch. In addition, the Raspberry Pi is a barebones computer, and that's not exactly a secret. Additional purchases will be required for most (and should be expected).
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