The attached image is a schematic of a Retropie hand held I've made.
The blank square you see is just a circuit board I created to make splitting up the power easier.
The audio amp gets it's signal from from the LCD audio out through HDMI.
The Teensy is connected through USB to the 3B+ for power and to run the M8 headless software.
It all works but the problem is the 3B+, the LCD and the Teensy draw way too much power and the battery drains too fast. Battery 1 lasts forever because the LED circuit and the audio amp draw very little power.
So here's my question, if I power the Teensy from battery 1 will it fry the teensy or the 3B+ because of the USB connection? In other words, if the teensy is supplied power will it continue to draw power from USB and/or possibly supply it to the 3B+ causing... issues?
Sorry if this is a dumb question but I only know enough about these things to get myself in trouble LOL I started out following this video: https://www.youtube.com/watch?v=x1RHdH-nlmg but I had to go off road because some of it just wouldn't work for me.
Any help would be really appreciated. And if you need more details please let me know what it might be.