Hi I have a Raspberry pi 4 which is used to drive a car for a project. Pi is powered using a hat connected through gpio ports. I am using 2 x 18650mah 3.7v for powering the car and rpi. Most of the time it shows Low voltage warning and the status lights starts to dim. Is there any way to power rpi without using the 5v pin in gpio and connecting an external power supply using Usb Power Bank. Also I found out that i accidently powered the rpi from both the gpio and the usb.
Have you tried to add a capacitor between GND and 5V close to the 5V pin? Maybe the voltage is not stable and drops on load changes.
If you want to power the Pi and the HAT seperately, the easiest way would be to just cut-off the 5V and 3.3V pins (but NOT the GND pins) on the pin header of the raspberry pi. This should work, but I have never done this myself.