So I have a project with ESP32 and SIM808 for GPS and GSM. I have done all the coding needed while testing it, but all this time I power it using USB. Now I need to make it portable and small, so I choose to use 3,7V 200mAh battery. I do the powering with a bit trial and error. At first I try to power SIM808 alone:
It works well. I know it because when I power on this module, the LED indicator blinking and soon blink every several second, indicate the modem initialized correctly and connected to a network.
I continue to wire it with ESP32. At first my design look like this:
I use one battery and connect it parallel with SIM808 and Stepdown module to convert 3,7v to 3,3v to the ESP. I connect all the ground together. It's in parallel so the voltage should be the same but with less current. And when I try to start the SIM808 (by pressing its button) it wont start. The LED indicator blink 3 times before it goes down, and while it going down, the ESP32 get restart as well. I press the button again but still the same. It blinks several times before shut down. SIM808 needs 2A current to for transmitting. I guess it lacks current due to parallel with ESP32.
I thought about using 2 different power source for ESP and SIM808. So I use 2 battery with same specs. I change my design to look like this:
I try to start the SIM808, and it can't. The same problem as before, but somehow, after I accidently pluck the power cable and put it back again, it somehow works. I can initiate the modem. But after sometime and GPS connected, ESP32 restart and I see that SIM808 going down as well. The LED indicator now off. When I try to turn it on again, it does the same as before. The LED indicator blink 3 times before it goes down.
I still very confuse with this problem. Anyone know how to power this project using Li Ion battery? Any hints are welcome.
