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Powering a Portable

Posted: Sun Mar 24, 2019 1:47 am
by Raspigamer

I have created a portable and want to upgrade the power circuit that I am currently using. I need something that can supply a decent amount of power and have come up with this setup:

Power Bank -> DC-DC Step Down -> Raspberry pi and other components.

I would want a power bank that allows me to use it and charge it at the same time. The portable runs on 5V and will need at least a 3-3.5A supply. Has anyone tried this or can verify that this set up would work? Also does anyone have suggestions for a power bank that has charge and play?

Re: Powering a Portable

Posted: Sun Mar 24, 2019 3:10 am
by Gavinmc42
I have used 7.2V 6 cell NiMH RC car battery packs.
Li-Ion cells have an issue with balance charging so they are tricky to charge and use at the same time.
The charger in effect has to be two systems, with perhaps ideal diode isolation.

LiPo, lithium polymers cells used for hobby RC planes and drones come in many sizes.
Balance chargers for theseare low cost but only for charging not powering at the same time.
The standard size cell 18650 or 26650 can be 3.7 Li-Ion or 3.2V LiFePO4.
I prefer the LiFePO4, simpler charging circuit.

Depending on how portable, cordless drill 18-20V packs with charger allows for charging one pack while using another.
Reduce the system complexity by using two packs, one on charge while using the other.
Complex power/charging circuits can cost more than a second battery pack.

Re: Powering a Portable

Posted: Sun Mar 24, 2019 3:29 am
by Raspigamer
What if i used something like this: ... 229ef1bf2d

It has the pass-through built into the bank. Do you think I could use something like this?

Re: Powering a Portable

Posted: Sun Mar 24, 2019 6:04 am
by Imperf3kt
It might work.
What you would need is a msle USB-C to male Micro USB-B cable (doesn't exist as far as I know, so you need male USB-C to USB-A female + male USB-A to Male Micro USB-B and as ll cables will need to be rated for around 3A)

Or you could tear it apart and solder your own, 3A or higher rated ports, or just wire it directly to your Pi with some way to turn it off.

Re: Powering a Portable

Posted: Sun Mar 24, 2019 2:04 pm
by Raspigamer
Thank you. If i found a powerbank that wasn't USB-C I would be able avoid alot of that converting cord mess. right?
Like this one: ... B01422TC14

Also will the current change when it runs through the DC-DC Step Down or will it stay the same? I've never worked with these components before and am not entirely sure of their effects other than lowering the voltage.

Re: Powering a Portable

Posted: Sun Mar 24, 2019 6:39 pm
by Imperf3kt
As long as the cable you use is up to delivering up to 18 watts, it would probably work.

Just wondering though, are you sure this is "portable" like this? A 20,000 mAh battery is quite large and heavy.

Re: Powering a Portable

Posted: Sun Mar 24, 2019 10:30 pm
by Raspigamer
Yes. I was just using that power bank as an example. Really all I need is some sort of power circuit that will provide 5V/4A and allow for pass-thru charging.