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WillBoxOwO
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A good battery for the Pi 3B+?

Thu Nov 01, 2018 11:58 pm

Hello.
For a project I want to make for myself, I want to make a portable computer.
Only problem, the battery. I want to power a 5v 1a speaker along with it. So basically, I need a battery that delivers a 5v 3a (for the pi) and another 5v 1a for the speaker. Id also like a leftover port (5v 1a) so I can charge my controllers (if possible)

So my questions are:
Where is the battery of my dreams?

And lastly, can I power the speaker trough the GPIO pins? My speaker has USB-in for power- It would be silly to ask the Pi to send an analog signal trough the 5v pins, lol.

Cheers.
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Imperf3kt
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 12:02 am

A regular phone charger battery pack will do what you want, but the hard part is finding one that actually holds its voltage stable, while delivering the advertised currents.

I personally doubt a Pi3B+ will run off any commercially available power bank.
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WillBoxOwO
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 12:16 am

Imperf3kt wrote:
Fri Nov 02, 2018 12:02 am

I personally doubt a Pi3B+ will run off any commercially available power bank.
Ohh, snap.
Would it be a good idea to make myself a power bank then? (Using an adafruit battery and a charger board thing?)
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W. H. Heydt
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 12:30 am

WillBoxOwO wrote:
Fri Nov 02, 2018 12:16 am
Imperf3kt wrote:
Fri Nov 02, 2018 12:02 am

I personally doubt a Pi3B+ will run off any commercially available power bank.
Ohh, snap.
Would it be a good idea to make myself a power bank then? (Using an adafruit battery and a charger board thing?)
First...how long do you want to system to run on the battery? Second...do you actually need a Pi3B+ (*the* most power hungry Pi out there)? Or would a Pi2B (much easier to power from a battery) do?

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WillBoxOwO
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 2:00 am

Im aiming for the Pi3B+ since I want to do emulation on the go.
Second, I was looking at 10 000-20 000 mAh batteries so it lasts the day. :)

Thanks for the quick response mate. <3
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W. H. Heydt
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 2:53 am

WillBoxOwO wrote:
Fri Nov 02, 2018 2:00 am
Im aiming for the Pi3B+ since I want to do emulation on the go.
Second, I was looking at 10 000-20 000 mAh batteries so it lasts the day. :)

Thanks for the quick response mate. <3
So you're looking at--without stating it--Li Ion or LiPo (probably the later). Those Ah rating are at the nominal cell voltage of 3.7v, so 10Ah = 37Wh. You're planning to power a device that can draw up to 2.5A at 5v, or 12.5W. So, in theory, you could run your Pi flat out for...3 hours on a 10Ah LiPo battery, or 6 hrs. on a 20Ah LiPo. Is 3 to 6 hours your definition of "all day"?

Understand that you will never meet that theoretical value because you can't safely run a LiPo cell completely flat, plus the voltage drops off, especially towards the end of the discharge cycle. On top of that, the voltage conversion circuit isn't 100% efficient--there are losses. At best you should only count on about 85% of the "rated" capacity being available. At worst...maybe 70%. So in reality, you may be looking at about 2.5 hrs. on a 10Ah battery.

For a data point... I can run a Pi2Bv1.1 + 7" RPF screen with keyboard, mouse and WiFi dongle attached for about 5 hours from 10.4Ah "powerbank". Most of that time, it isn't doing much, so it's running well below max power draw. A Pi3B+ wouldn't do as well, and a Pi3B+ doing doing continuous compute-intensive work wouldn't even come close to running that long.

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mikronauts
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 3:21 am

Fyi, I run Pi3's (not 3b) off usb power banks all the time, so I see no reason a 3b would not run off a good power bank. I will try it soon, I need to test a 3b based robopi bog anyway.

Imperf3kt wrote:
Fri Nov 02, 2018 12:02 am
A regular phone charger battery pack will do what you want, but the hard part is finding one that actually holds its voltage stable, while delivering the advertised currents.

I personally doubt a Pi3B+ will run off any commercially available power bank.
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

PhatFil
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 3:28 am

Take a look at the battery packs sold to motorists as flat battery boosters. these can deliver a high amp drain (over 50a) @12v and may also support higher than usual capacity on its usb outputs too but if not a small 4-5a capacity dc-dc converter to drop 12 to 5v for the pi supply should be easy enough to sort out.

W. H. Heydt
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 4:24 am

mikronauts wrote:
Fri Nov 02, 2018 3:21 am
Fyi, I run Pi3's (not 3b) off usb power banks all the time, so I see no reason a 3b would not run off a good power bank. I will try it soon, I need to test a 3b based robopi bog anyway.
Excuse me? What Pi3s do you run that are not Pi3Bs, or Pi3B+s? Are you using CM3 or CM3L? I really wish we had a Pi3A/Pi3A+, but unless you know something important that the rest of us have missed, those don't exist in the wild.

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Imperf3kt
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 8:16 am

:idea:
PhatFil wrote:
Fri Nov 02, 2018 3:28 am
Take a look at the battery packs sold to motorists as flat battery boosters. these can deliver a high amp drain (over 50a) @12v and may also support higher than usual capacity on its usb outputs too but if not a small 4-5a capacity dc-dc converter to drop 12 to 5v for the pi supply should be easy enough to sort out.
This here is the exact problem.
Find me a decent regulator that doesn't experience nanosecond power drops when the current draw increases (a main contributor to the 'lightning bolt' low voltage warning)
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drgeoff
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 9:55 am

Imperf3kt wrote:
Fri Nov 02, 2018 8:16 am
Find me a decent regulator that doesn't experience nanosecond power drops when the current draw increases (a main contributor to the 'lightning bolt' low voltage warning)
An appropriate capacitor will easily cover up to several milliseconds of power drops from a PSU.

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mikronauts
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 12:22 pm

Sorry, I meant not pi3b+'s ... I inadvertantly left out the '+'

I am still waiting for pi3a or pi3a+ boards.

(Typos mostly due to using a tzblet to post, as I am away from my office)
W. H. Heydt wrote:
Fri Nov 02, 2018 4:24 am
mikronauts wrote:
Fri Nov 02, 2018 3:21 am
Fyi, I run Pi3's (not 3b) off usb power banks all the time, so I see no reason a 3b would not run off a good power bank. I will try it soon, I need to test a 3b based robopi bog anyway.
Excuse me? What Pi3s do you run that are not Pi3Bs, or Pi3B+s? Are you using CM3 or CM3L? I really wish we had a Pi3A/Pi3A+, but unless you know something important that the rest of us have missed, those don't exist in the wild.
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W. H. Heydt
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 1:46 pm

mikronauts wrote:
Fri Nov 02, 2018 12:22 pm
Sorry, I meant not pi3b+'s ... I inadvertantly left out the '+'

I am still waiting for pi3a or pi3a+ boards.

(Typos mostly due to using a tzblet to post, as I am away from my office)
So I see... Thanks for the clarification.

lewmur
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 4:31 pm

There a plenty of Power Banks on eBay for under $15 that will work just fine. What you have to realize is that the 3B+ itself will run just fine from a Power Banks 2A output. The only time you'd need more than 2A would be if you were really loading the USB ports. And since you'd be powering your USB speaker from the second output of the Power Bank, I can't imagine what else you'd have plugged into the USB bus that would overload the 2A supply. Keyboard, Mouse and external 2.5" HDD certainly wouldn't.

LTolledo
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 10:31 pm

for all day power (or probably more) I'd probably go for a couple of 12D batteries in parallel, then convert it 5.2V at 4A and use custom cable (using VCT 2x0.75mmsq ) for power connection to RPi3B+ (not use microUSB)

batteries charged via mains converter or solar, wind/water turbines....
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lewmur
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 11:08 pm

Ever heard of the term "overkill"? What would your solution cost vs a 5ah Power Bank for $12?

LTolledo
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Re: A good battery for the Pi 3B+?

Fri Nov 02, 2018 11:20 pm

lewmur wrote: Ever heard of the term "overkill"? What would your solution cost vs a 5ah Power Bank for $12?
yes, and I kinda liked the term... ;) using a TESLA Model S power bank to power an RPi will probably be an "overkill"
the OP did not mention cost restraints.....

I also like cats (or Felis silvestris catus) too. :D
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 3:37 am

So, your intent was to mock the OP for not stating the obvious? One should always state cost as being part of the criteria for a Pi solution? If that is the case, you should have started with the Tesla battery.

LTolledo
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 3:53 am

Have no intention to mock the OP

in my post
LTolledo wrote: .....I'd probably go for a couple of 12D batteries in parallel....
so if it were me... am stating.

If you feel offended on how I intend to power up my RPi using batteries then that's your problem.
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

W. H. Heydt
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 4:00 am

lewmur wrote:
Sat Nov 03, 2018 3:37 am
So, your intent was to mock the OP for not stating the obvious? One should always state cost as being part of the criteria for a Pi solution? If that is the case, you should have started with the Tesla battery.
Well...there is an "obvious" that still hasn't been stated, except in the loosest terms. To wit...when you say that you want this rig to run "all day", what exactly do you mean? How many hours of continuous operation do you want?

Secondarily, it would help if you could set up your system (using mains power) and measure the current draw when running in a way typical to what you anticipate.

With those two items, it will be possible to make a reasonably informed estimate of what battery capacity it will take to do what you want to do.

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Imperf3kt
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 12:43 pm

A 5Ah battery won't last 'all day', it won't even last half a day.
At best, it should last around 6 hours - if the Pi has nothing else attached and does absolutely nothing other than sit there, turned on.
So I think the accusation of overkill here, is unjustified and that there is no overkill at all
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 1:38 pm

Retired disgracefully.....

W. H. Heydt
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 4:17 pm

Well...that should be good for, perhaps, 4 hours. And even then, it assumes that the Pi3B+ will be running with relatively little drain on the USB ports (not that battery will only provide 5v at 2A).

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WillBoxOwO
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 5:16 pm

lewmur wrote:
Fri Nov 02, 2018 4:31 pm
The only time you'd need more than 2A would be if you were really loading the USB ports. And since you'd be powering your USB speaker from the second output of the Power Bank, I can't imagine what else you'd have plugged into the USB bus that would overload the 2A supply. Keyboard, Mouse and external 2.5" HDD certainly wouldn't.
Okay. So if I plug my old SSD, a bluetooth mouse and 1 USB drive from times to times, your telling me that the overclocked Pi (1.5Ghz) running at 100% usage most of the time wont show any lightning bolt? Lets not forget the screen too... :shock:
Thanks for the link my friend!

So, this battery should do the trick, right...? Where should I plug the speaker...? GPIO? I dont see any secondary USB ports...

**And talking about budget, the ones that told I had a limited budget got it right. I want to spend 60-80$ overall (if its possible) but I wont hesitate to spend a little more, itll just take more time to get the parts. :)
W. H. Heydt wrote:
Sat Nov 03, 2018 4:17 pm
Well...that should be good for, perhaps, 4 hours.
4 hours is more than acceptable. :mrgreen:
W. H. Heydt wrote:
Fri Nov 02, 2018 12:30 am
First...how long do you want to system to run on the battery?
3 to 6 hours. Sorry, I didnt really answered you clearly there.
LTolledo wrote:
Sat Nov 03, 2018 3:53 am
Have no intention to mock the OP
Thanks, lol.

Thanks everyone for the amazing support! ;)
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W. H. Heydt
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Re: A good battery for the Pi 3B+?

Sat Nov 03, 2018 5:33 pm

WillBoxOwO wrote:
Sat Nov 03, 2018 5:16 pm
lewmur wrote:
Fri Nov 02, 2018 4:31 pm
The only time you'd need more than 2A would be if you were really loading the USB ports. And since you'd be powering your USB speaker from the second output of the Power Bank, I can't imagine what else you'd have plugged into the USB bus that would overload the 2A supply. Keyboard, Mouse and external 2.5" HDD certainly wouldn't.
Okay. So if I plug my old SSD, a bluetooth mouse and 1 USB drive from times to times, your telling me that the overclocked Pi (1.5Ghz) running at 100% usage most of the time wont show any lightning bolt? Lets not forget the screen too... :shock:
The mouse doesn't really count. While the BT circuit has to be powered by the Pi, the mouse itself, isn't. The monitor only counts if it's being powered by the Pi.

The safe way to figure the power requirement is to assume the Pi is pulling all the power it can: 2.4A.
Thanks for the link my friend!

So, this battery should do the trick, right...? Where should I plug the speaker...? GPIO? I dont see any secondary USB ports...
You could power the speakers from a USB port (5v GPIO is on the same circuit, so the load is the same either way). Or you could find an large enough battery set up this way: https://www.monoprice.com/product?p_id=15120 Use the 2.4A port for the Pi and the 1.5A port for the speakers. Mind you, you'll be lucky to get 3 hours out of it if you run the Pi flat out. Monoprice has other units up to 27.2Ah, but they all limit the output to 2A on a single port.
W. H. Heydt wrote:
Fri Nov 02, 2018 12:30 am
First...how long do you want to system to run on the battery?
3 to 6 hours. Sorry, I didnt really answered you clearly there.
What I would suggest is that you get the Monoprice 10.4Ah unit and test it to see if it will run what you want to run and for how long. If it doesn't work, you're not out much and you have a battery that will happily recharge cell phones or tablets, should you have any. If it works, but doesn't run long enough, consider the idea of being able to shut down and switch batteries, and then carry a spare or two. (That is what I do if I think I'm going to need more run time on my note taking Pi2B/7" display system...I have one of those 10.4Ah units, and one of their 10Ah units.)

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