jesxs
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Best way to power a raspberry pi 3b+

Tue Jun 09, 2020 2:11 pm

So I'm making a little wardriving device with a raspberry pi 3b+. I will be carrying an Alpha network antenna and a gps receiver, as well as a 3.5" screen.
I have a 12000mAh external battery;

https://imgur.com/WFl9yy5

I connected the raspberry to the usb which says '2A OUT' on the battery, but the raspberry would keep restarting itself on boot.
Is there any component I can add to be able to use this battery?

Thanks in advance

DarkElvenAngel
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Re: Best way to power a raspberry pi 3b+

Tue Jun 09, 2020 2:18 pm

Your power back says 1A output and 2A input.

It might not be able to give the power you need. Do you have a picture of where it says 2A out?

jesxs
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Joined: Sat May 18, 2019 12:18 pm

Re: Best way to power a raspberry pi 3b+

Tue Jun 09, 2020 2:26 pm

DarkElvenAngel wrote:
Tue Jun 09, 2020 2:18 pm
Your power back says 1A output and 2A input.

It might not be able to give the power you need. Do you have a picture of where it says 2A out?
https://imgur.com/hm0XjkO

Its not a really high quality battery or anything so I wouldn't really trust that, but anyway, it would be nice if I could use what I already have.
If not, what options do I have?
I'm not an expert in the field so I'm worried that I'll get a PSU or something and then it wont be enough.
I've been looking at something like this

https://www.amazon.es/dp/B07HK5VGB6/ref ... ljaz10cnVl

DarkElvenAngel
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Re: Best way to power a raspberry pi 3b+

Tue Jun 09, 2020 2:39 pm

jesxs wrote:
Tue Jun 09, 2020 2:26 pm
DarkElvenAngel wrote:
Tue Jun 09, 2020 2:18 pm
Your power back says 1A output and 2A input.

It might not be able to give the power you need. Do you have a picture of where it says 2A out?
https://imgur.com/hm0XjkO

Its not a really high quality battery or anything so I wouldn't really trust that, but anyway, it would be nice if I could use what I already have.
If not, what options do I have?
I'm not an expert in the field so I'm worried that I'll get a PSU or something and then it wont be enough.
I've been looking at something like this

https://www.amazon.es/dp/B07HK5VGB6/ref ... ljaz10cnVl
I've never used anything like that so I can't say for sure if it would or wouldn't work. It looks promising though.

I have had mixed results with power banks sometimes the cheap ones work great and the expensive ones don't. Looking for something purpose made to power a Pi would be your best bet.

I would say that one you have just isn't up to task.

jowage
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Re: Best way to power a raspberry pi 3b+

Tue Jun 09, 2020 3:59 pm

that battery bank looks very suspect indeed, problem with most affordable USB powerbanks are only built to handle normal USB use which is nearly always under 2A. If your peak current surge won't be over 2A I think you can easily get away with a good quality 2A rated powerbank.

For one of my battery projects I use a larger screen and quite a bit of peripherals and best solution I came up with is using 12V (3 cell) LiPo batteries from the RC hobby with a simple step-down module rated for 5V 5A continuous operation, LiPo's are far more expensive and dangerous than for example 18650 cells but the charging and cell-balancing is made easier with ready-to-buy components/devices from RC hobby stores (less electronics skills needed).

jesxs
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 8:27 am

jowage wrote:
Tue Jun 09, 2020 3:59 pm
that battery bank looks very suspect indeed, problem with most affordable USB powerbanks are only built to handle normal USB use which is nearly always under 2A. If your peak current surge won't be over 2A I think you can easily get away with a good quality 2A rated powerbank.

For one of my battery projects I use a larger screen and quite a bit of peripherals and best solution I came up with is using 12V (3 cell) LiPo batteries from the RC hobby with a simple step-down module rated for 5V 5A continuous operation, LiPo's are far more expensive and dangerous than for example 18650 cells but the charging and cell-balancing is made easier with ready-to-buy components/devices from RC hobby stores (less electronics skills needed).
I like that. I'll probably look into that. Thanks :D

jesxs
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 9:27 am

jowage wrote:
Tue Jun 09, 2020 3:59 pm
that battery bank looks very suspect indeed, problem with most affordable USB powerbanks are only built to handle normal USB use which is nearly always under 2A. If your peak current surge won't be over 2A I think you can easily get away with a good quality 2A rated powerbank.

For one of my battery projects I use a larger screen and quite a bit of peripherals and best solution I came up with is using 12V (3 cell) LiPo batteries from the RC hobby with a simple step-down module rated for 5V 5A continuous operation, LiPo's are far more expensive and dangerous than for example 18650 cells but the charging and cell-balancing is made easier with ready-to-buy components/devices from RC hobby stores (less electronics skills needed).
Did you set 5V 5A as an optimal output for what you use or it doesnt need to be so precise?
Again I'm new in this world so I'm thinking, can 5A be dangerous for the rpi?
As I said before I plan on using a 3.5" screen, gps receiver, alfa network card and a little fan attached to the pi

pfletch101
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 3:40 pm

jesxs wrote:
Wed Jun 10, 2020 9:27 am
Did you set 5V 5A as an optimal output for what you use or it doesnt need to be so precise?
Again I'm new in this world so I'm thinking, can 5A be dangerous for the rpi?
As I said before I plan on using a 3.5" screen, gps receiver, alfa network card and a little fan attached to the pi
A power supply needs to have a current rating that gives at least a comfortable (I would use 20%) margin over what the equipment connected to it will draw under worst case conditions. However, it would perfectly safe to connect a 5V power supply with a 50A rating to a Pi. Th Pi will only draw the current it needs. The only downsides of using a power supply with a much higher current rating than you need are its likely increased cost and probably its ongoing power usage - power supplies tend to be most efficient near their rated output current.

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davidcoton
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 5:16 pm

pfletch101 wrote:
Wed Jun 10, 2020 3:40 pm
The only downsides of using a power supply with a much higher current rating than you need are its likely increased cost and probably its ongoing power usage - power supplies tend to be most efficient near their rated output current.
There is a downside with an over-powerful PSU. The Pi3B+ is designed with a 2.5A (carry current) polyfuse and a TVS diode for reverse - and over-voltage protection. All is well if power is applied through the USB socket. However, powering via the GPIO header will bypass the polyfuse, so under fault conditions the full PSU current can flow through the Pi tracks and TVS diode. Current over about 4A will eventually lead to TVS failure and possible track damage. So if using a supply capable of over 4A and connected via the GPIO header, an external polyfuse should be used.

On the Pi4B there is no onboard polyfuse, so the external polyfuse is desirable even if the high-current supply is connected via the USB -C socket.
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pfletch101
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 8:15 pm

davidcoton wrote:
Wed Jun 10, 2020 5:16 pm
pfletch101 wrote:
Wed Jun 10, 2020 3:40 pm
The only downsides of using a power supply with a much higher current rating than you need are its likely increased cost and probably its ongoing power usage - power supplies tend to be most efficient near their rated output current.
There is a downside with an over-powerful PSU. The Pi3B+ is designed with a 2.5A (carry current) polyfuse and a TVS diode for reverse - and over-voltage protection. All is well if power is applied through the USB socket. However, powering via the GPIO header will bypass the polyfuse, so under fault conditions the full PSU current can flow through the Pi tracks and TVS diode. Current over about 4A will eventually lead to TVS failure and possible track damage. So if using a supply capable of over 4A and connected via the GPIO header, an external polyfuse should be used.

On the Pi4B there is no onboard polyfuse, so the external polyfuse is desirable even if the high-current supply is connected via the USB -C socket.
In context, you are probably right to mention this consideration, though one would only experience the issue if there has already been a catastrophic failure on the Pi board, or (much more likely) one of the peripherals plugged into the USB sockets is drawing more than the rated power for the socket.

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davidcoton
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 10:02 pm

pfletch101 wrote:
Wed Jun 10, 2020 8:15 pm
one would only experience the issue if there has already been a catastrophic failure on the Pi board, or (much more likely) one of the peripherals plugged into the USB sockets is drawing more than the rated power for the socket.
or if there is a PSU failure (rare, I think)
or an ID10T error involving wiring of the supply (polarity reversal is not as rare as it should be).

USB power output should be separately protected on Pi1, 2, 3, 4. Not on Pi0, probably not on a Pi4 using USB-C as a power output.

Ask H__t_r about applying 12V (IIRC) to a Pi. It is survivable (once). Removal of the TVS diode and repeat mistake is terminal.
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jesxs
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 10:13 pm

Thank you everyone for your responses.
For what I've read, the safest thing is to power it via usb, and about 5A (with the usb dongles I mentioned) I think would be enough. Correct me if I'm wrong.
I've looked into these

https://www.amazon.es/dp/B00ISTGQSU/ref ... 4EbYQ0M1M9

Plus an UBEC, but apparently that would be powering it via gpio, right?
The thing is I would have to solder the gpios under the pi because the lcd screen takes almost all of them (maybe not, but better be safe) so I'd like to avoid this.

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davidcoton
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 10:34 pm

The maximum total current output of the USB sockets of a Pi3B+ is 1A2. The maximum current required with that USB load is 2A5.
Location: 345th cell on the right of the 210th row of L2 cache

jesxs
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Re: Best way to power a raspberry pi 3b+

Wed Jun 10, 2020 10:37 pm

davidcoton wrote:
Wed Jun 10, 2020 10:34 pm
The maximum total current output of the USB sockets of a Pi3B+ is 1A2. The maximum current required with that USB load is 2A5.
Ahh I didn't got it. I feel stupid, sorry again if these questions are really dumb.
Thank you :D

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