Split power to Pijuice

Hey, I’m trying to work through building a handheld gaming device centred around a Raspberry Pi 4 / Pijuice / and a 10 inch screen (I tested the screen on a 5v 1amp usb power adapter and it was fine).

So far I have the Pi 4 and Pijuice connected fine, however I’m trying to figure out how I can power the screen. The screen can be typically be powered just fine from a USB socket but its too much to power it directly from a spare USB output on the Pi…I tried it, nothing works (and I understand the P4 is pushing the power limit of the Pijuice anyway).

So I’m left with either powering it from a separate portable battery pack or try and find a way to power it from the same battery as the Pijuice.

I was wondering…

If I bough this battery: https://core-electronics.com.au/3-pin-lipo-battery-for-pijuice-20000mah.html and split the red and black into an additional JST connector, that would effectively give me two outputs:

A: 3.7v + NTC temperature sensor lead (connected to Pijuice, and Pijuice can still do all of its battery management magic…I would also charge via the Pijuice)

B: 3.7v JST connected to this: https://core-electronics.com.au/powerboost-500-charger-rechargeable-5v-lipo-usb-boost-at-500ma.html this is the only thing I could find that would take a Lipo input and convert it into a USB output that I can then power the screen with

I checked the specs on the battey and it says the max continuous discharge it 1c, which I ‘think’ at 20,000ma means its can safely sustain 20amp at 3.7v…which should be well within spec.

…I want to check all this as I basically made it all up and have not idea if I’m just going to fry everything trying?!

Hey Oliver, we’re multiplying!

The Pi 4 can output 1.2A (total) over USB: https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.md

If the screen isn’t turning on, something else is probably wrong. The Pi itself will only pull about 600mA at idle.

But otherwise, yes your idea will work.

Ah, hi Oliver!

You comment made me have another go at powering the monitor via the USB on the PI…I got it to work my booting and then connecting the USB for power, for some reason I refuses to boot with the monitor power plugged in…

Thanks for confirming my idea will work, I think I might go down that route…while a bit more work at least I know I have extra power headroom on the PI to connect some other stuff.

Thanks for your help!


Hi Oliver,

There are a lot of us now! Glad to hear you’ve got it sorted, and yes I agree with Oliver33 that your idea is sound in principle.

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