Pi 4 came out with power requirements of 5V@3A. In reality, using a 3rd party power supply will result in a low voltage warning even if the power supply can provide 3A. The reason lies in voltage drop. Pi 4 board sends a warning if voltage drops below a certain value (about 4.75V based on my measurements).

I’ve done measurements with a 100W laptop charger which is rated for 3A at 5V. Under load, voltage drops from 4.95V to 4.75V, which triggers the low voltage warning. That’s why the official 15W power supply is rated for 5.1V@3A, 0.1V higher than the USB specification. With Pi 4 you can just ignore the warnings, as even an overclocked board with 2 external HDDs fits into 15W.

With Pi 5 the situation turns around. An overclocked board alone draws 2.5 amps, leaving no space for USB devices. The new official power supply is now rated for 5.1V@5A, which you can’t replace with a charger from your junk box full of spaghetti cables and random chargers. So why not just buy an official RPi power supply? Even if it’s priced reasonably, I don’t like the idea of saving $2 on a PD chip and then spending $12 on a power supply and being tied to that specific power supply and that specific cable length.

So I checked my junk box and found a PD trigger board, an XL4015 DC-DC converter, and some wiring. I set the output voltage to 5.15V and soldered wires to the GPIO adapter that was bundled with the NVMe HAT. I used 2 pins for 5V and 2 pins for GND, as single pin couldn’t handle 5 amps.

So now Pi has a Power Delivery–compatible power system (actually it works with almost any quick-charge protocol). This means it can be powered from basically any fast charger. The PD trigger board asks the power supply for 20V (or the highest voltage it supports if 20V isn’t available), then this voltage is converted down to 5.15V using the XL4015 module. The Pi itself is powered through the GPIO pins, bypassing the USB-C input entirely.

As a result: no warnings, one additional USB port, and additional voltage to power other accessories (e.g. 12V fan, monitors, 3.5" drives—you name it), all using a single Type-C cable.