I want use my NodeMCU to drive a SIM808 Module with integrated LiPo Charger. https://www.itead.cc/wiki/SIM808_GSM/GPRS/GPS_Module
There are two problems. First of all the SIM808 Module just provides the LiPo Voltage, no steady 3.3V or 5V output. The NodeMCU needs 3.3V (or 5V with LDO). The internal LDO has a high quiescent current of >1mA. So the idea would be to replace the onboard 5V to 3.3V LDO with one with a low quiescent current (<0.1mA) for direct LiPo input (3.7-4.3V) and 3.3V output which is pin compatible to just replace it direcly on the NodeMCU.
The MCP1700 would be an option as TO92 to make the PINs fit because VIN/VOUT is reversed.
This would be my easiest idea. Do you have any different ideas?
More about the NodeMCU and the AMS1117 position on the board https://tinker.yeoman.com.au/2016/05/29/running-nodemcu-on-a-battery-esp8266-low-power-consumption-revisited/