Powering TTGO T-Call (ESP32 + SIM800L board) with only battery
The question on powering the TTGO-TCALL was answered through many experiences in this issue: https://github.com/Xinyuan-LilyGO/LilyGo-T-Call-SIM800/issues/29.

This video: https://www.youtube.com/watch?v=R-qp-GwPrRk goes into more details about the behavior of the IP5306.

This comment lists the I²C registers and what they do: https://github.com/m5stack/M5Stack/issues/135#issuecomment-476305363, since it's originally in Chinese and I can't find it in English (read the data-sheet along with it to know which bits are being referenced since some are reserved).


I don't really have an answer to your question, but I thought this might help.