Battery power supply for SBC and screen


Laptop und Trachtenjanker
Oct 8, 2008
the mockracy
I want to run a single board computer - likely an Orange Pi 5 - and a screen on batteries. The board needs 5 V, the screen 12 V. I've read around a bit, and apparently using two voltage regulators for each item should do the trick. Which is baffling to me since reading about voltage dividers. Will that work without magic smoke?

Should I go with one big cell, or a number of small cells in parallel, and step-up regulators? Or four cells in series, and step-down regulators? I could use cylindrical cells with a protection circuit, and charge them in a dedicated charger. Which I'm not a fan of: inconvenient, big and heavy. Would rather use pouch cells. Which are also available with protection, but can't easily be charged externally.

Disregarding the options above - if possible I'd like to have the additional convenience of plugging in and charging this monstrosity during usage, just like a phone or laptop. Will a/any BMS do that?

What's important: Not killing myself in a fiery disaster and readily available parts.

These things are nebulous to me, and the options are plentiful - thank you in advance for your input!

Edit: I found this UPS for raspberry pi
Claims up to 6 Amps, that should sort out the Pi 5. The pins wouldn't line up though, so that's a hassle. And I'd want to remove the battery holders because of their size, and replace them with a connector for a pouch cell. I'd likely make a mess there, the holder looks surface mounted.

Edit: I learned that pouch cells usually are li-po as opposed to NMC cylindrical cells and are not interchangeable.
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ok, slow down a bit. what batteries do you have access to? this will determine the solution for you.
linear regulators are not a good idea as they are not efficient and waste power via heat. This means a resistor voltage divider like you first said or the traditional 7805 voltage regulators.

the ideal would be at least 2 18650 cells giving 7.2V nominal 8.4 fully charged. then using some cheap ebay buck converters to get 5V at 3A for the orange Pi and a boost converter to get your 12V for the screen .
I have seen LCD screens rated at 12V work quite well on a lower voltage so the option to use 3 18650 cells for a 12.6V full charge and usable down to around 10V would power the screen directly and then just the 5V buck converter for the 5V to run the Pi . depending on the cells 2000mA capacity is about average. Reclaimed laptop batteries are usually 2000mA. a simple $2 3 cell BMS will protect the cells and charging of them. if 2000mA are not enough of a run time the simply parallel them so 6 cells in a 3S2P config will work fine and the same BMS is ok for both. The number of batteries will be determined by how long you want this system to run. the Pi will take more power than the screen . so the 3s2p battery would last about an hour to hourand a half depending on how hard the pi is running.

I build 18650 cell battery packs all the time. Built one a week ago with a variable put put on the converter to give me 8V to drive my Canon camera from a large pattery pack for Astrophotography.
Just saying: Usb-C is multi voltage.
So a powerbank with usb-c port is all what is needed. You can just grab a 12V usb cable if you dont want to wire the pins yourself.
Or if you insist on building your own battery, this is at least where you can source reliable parts from.
I would say something like elw3 stated. Try to use off-the-shelve components if that's an option. If you didn't buy any hardware yet, you probably can get an SBC + screen both using USB-C and use a regular powerbank for power.
If you use a 5V lipo you probably can use the 5V directly (still regulated) and a boost converter for the 12V.

It might also be implied you want it to work in a mobile setting, not a fixed location but having a back-up battery (like a UPS). So you have some requirements for mobility, like weight, size and ease of use.
If not, it will be a lot easier. I assume this setup is too big for you: