Comment by palmotea

> We chose a cheap off-the-shelf switchable voltage 20W hand-crank generator marketed for emergency USB charging. The Pi normally draws around 1.5A, but when it’s working hard (as it does when doing inference on the CPU), its current requirements can increase substantially, causing the generator voltage to sag below the Pi’s required 4.8V or even, in the case of a momentary 5A spike, to trigger the generator’s internal overcurrent protection and shut off the voltage output entirely, causing the Pi to brown out.

> To ensure the Pi sees a steady voltage when the full inference stack kicks in (and to afford crankers a little rest), we built a custom capacitor board [https://docs.google.com/spreadsheets/d/1Zv_Hsinvx_sWtdur4iWY...] to smooth out the generator’s output and act as a short-term (~20 second) power reservoir.

Somewhat off-topic, but could this capacitor board work with a small-ish 5V USB solar panel? I'm not great with electronics, but it seems like just the solution for a device I want to run with the panel.

My vague impression was it's not kosher per the USB spec to just stick a capacitor across the supply to even out the brown-outs, but this looks like it's doing some other stuff.