I'm trying to make an UPS for my Raspberry Pi 3.
In theory, it should provide 5v (output of the MT3608) when powered either from USB wall charger or from 18650 battery (through the TP4056). The Mosfet will do the switching between mains and battery.
When I power my RPi, it boots but then it enters on a boot-loop which is reported to be caused by low voltage (see: https://elinux.org/R-Pi_Troubleshooting#Raspberry_Pi_shuts_down_.28or_restarts.29_soon_after_booting_up).
I meassured the output voltage and it is stable when the RPi is off as well as when it is on (4.9v ~ 5.1v). The boot up sequence tipically consumes about 150-300mA on a Raspberry Pi B+ I use to prototype.
When the same wall charger is connected directly to the microUSB port on the RPi, everything works flawlessly.
18650 battery is a Samsung INR 18650 25R.
What could be causing the current drop? I'm considering replacing the MT3608 with an USB DC-DC Booster 0.9v-5v (https://www.ebay.com/itm/132487410767) but running out of ideas...