How to split the output of a PowerBoost supply card

[KillyGourou]

Hello everybody!

So i'd like to know if there is a easy solution to split the power output of this card : https://www.adafruit.com/product/2465

In fact, i would like to use it to power a Raspberry PI 3 B and a screen https://www.adafruit.com/product/1678 at the same time.

So I have to split the output to a micro-usb on one hand, and to a 2.1mm center-positive DC jack one the other hand.

Is that possible and do you know how to do it?

Also, we wanna use an ATXraspi to have a power led and button. The ATXRaspi can have a DC input OR a micro usb, and outputs a Micro USB for the RPI. It would also be a good idea to have the screen plugged into the ATX so that it's not powered on when the RPI isn't.

Any advice on how to handle this ?

Thanks

[abrugsch]

A Pi3 AND a HDMI screen might be asking a bit much of a powerboost 1000 tbh... also depends on the discharge rating of your chosen battery...
Pi3's can draw quite a bit of power.
BUT assuming all your stuff comes in at around or under 2A then you can use a power strip. either order one (well 3) of @helder's from OSHPark
or make your own (search for power strip, but it's a basic electrical tenet: you can literally 'split' the power into parallel lines and still have 5v usually called a 'rail' and what actually gets split is the current so if you have something that takes 0.5A and something else at 0.8A, both will be at 5V but before the split the current will be 1.3A and 'split' at the join to 0.8 and 0.5 after )

[KillyGourou]

First, thank you very much for your answer

A Pi3 AND a HDMI screen might be asking a bit much of a powerboost 1000 tbh... also depends on the discharge rating of your chosen battery...

At the moment, we didn't really chose the battery. We are looking for a great way to do it So if you have any good references :p

Pi3's can draw quite a bit of power...

Yep! For what i see, the screen we are looking for have an electric consumption of 500mA maximum so 2A might be enough to power the whole thing!

or make your own (search for power strip, but it's a basic electrical tenet: you can literally 'split' the power into parallel lines and still have 5v usually called a 'rail' and what actually gets split is the current so if you have something that takes 0.5A and something else at 0.8A, both will be at 5V but before the split the current will be 1.3A and 'split' at the join to 0.8 and 0.5 after )

As you can see, I'm not really used to electronics. Can this power strip look like I just connect both of my couples of wire at the output of the powerboost, which will give 5V and the current (2A) will be distributed depending on what the hardware need?

[abrugsch]

As you can see, I'm not really used to electronics. Can this power strip look like I just connect both of my couples of wire at the output of the powerboost, which will give 5V and the current (2A) will be distributed depending on what the hardware need?

yes exactly. the hardware will draw (in current) what it needs, as long as your source can supply it.
lithium batteries are very sensitive to having too much current drawn, typically you want no more than 1c (unless the battery is rated otherwise)
where 1c is approx the mAh rating but in Amps.
so for a theoretical 2500 mAh battery, that's 2500mAh at 3.7 v (before it's boost converted to 5V.) the conversion isn't lossless, ~90% efficient for the 1000c if I remember right
1c of 2500 mAh is 2.5A at 3.7v

to work out what that needs to be for 5v, lets say you need 2.1 A.
2.1x5 = 10.5watts
10.5/3.7 = 2.84A
+10% (for the loss in efficiency) brings us to just over 3A@3.7v
the 1c rating for the 2500mAh battery is 2.5A, but we need 3A. so a 2500 mAh 3.7v battery will struggle in this example

[KillyGourou]

to work out what that needs to be for 5v, lets say you need 2.1 A.
2.1x5 = 10.5watts
10.5/3.7 = 2.84A
+10% (for the loss in efficiency) brings us to just over 3A@3.7v
the 1c rating for the 2500mAh battery is 2.5A, but we need 3A. so a 2500 mAh 3.7v battery will struggle in this example

OK! I think i got it for the theory ^^

But i'm browsing to find a battery that allow the system to work for like 4 hours without any strugle with no good result.

I have the following formula to calculate the living time of a battery:

I = Q\T

Where:
I = current drawn by the system (A)
Q = capacity of the battery (Ah)
T = Living time of the battery (h)

So, if the system drew 3 A and if I want the battery to last 4 hours, Q = 12Ah, 12000mAh which looks like huge to me.

Is that correct?

And by the way, to you know any battery's model that can help me?

Thank you again

[abrugsch]

So, if the system drew 3 A and if I want the battery to last 4 hours, Q = 12Ah, 12000mAh which looks like huge to me.

Is that correct?

And by the way, to you know any battery's model that can help me?

Thank you again

yes, except it's even worse than that...
3A is a LOT for a handheld but it's also 3A @5V which is 15W.

at 3.7v (which is what your battery supplies most of the time) 15W is over 4A (15 / 3.7 = 4.05A)

so now you need 4A x 4h = 16 Ah! (+ 10% because of losses)
basically I think you need to discover exactly how much power your Pi3 + HDMI screen is going to draw because in reality I don't think a Pi3 is drawing 2.5A all the time playing emulators, but you might find otherwise. similarly you need to find out what your screen will be drawing at 5v, which may not be the same as at 12v (which that screen can take) but you're probably going to need to power the screen from a separate battery

[Cyborg_delta1]

The issue is the 1000c will not supply enough power to power the Pi3 and a HDMI screen you need the Power boost 1000b

https://www.adafruit.com/products/2030

It can power up to 4A on a 1.8v+ supply but you will need a separate charging circuit

like this http://tinyurl.com/hbofw22

or if the battery has a built in over charge/discharge protection then this http://tinyurl.com/hp4djcd

Or just check this out http://www.sudomod.com/forum/viewtopic.php?f=13&t=1607

[KillyGourou]

yes, except it's even worse than that...
3A is a LOT for a handheld but it's also 3A @5V which is 15W.

Naaaaaah... looks quite hard to handle with :/
I mean, a battery with this capacity isn't easy to find.

And by the way, I want the system to be compact so a second battery for the screen might be too much..

Btw thanks you very much

PS: Can I PM you for any further informations? (just in case )

[KillyGourou]

The issue is the 1000c will not supply enough power to power the Pi3 and a HDMI screen you need the Power boost 1000b

https://www.adafruit.com/products/2030

It can power up to 4A on a 1.8v+ supply but you will need a separate charging circuit

like this http://tinyurl.com/hbofw22

or if the battery has a built in over charge/discharge protection then this http://tinyurl.com/hp4djcd

Or just check this out http://www.sudomod.com/forum/viewtopic.php?f=13&t=1607

Hey,

Thank you for thoses links, I'll look at it and keep you informed but it look very interesting

[abrugsch]

PS: Can I PM you for any further informations? (just in case )

sure, but better to just post here so that everyone gets the benefit (or post a new thread and @Mention me. just putting @abrugsch in a post will give me a notification)