It's been a while since I've posted an update for this project but I have been making progress on the firmware. Everything except for the USB PD code and a master state machine is finished. I successfully got it charging 4S batteries this last week. My plan is to try and get this to a state where I would be comfortable sending people beta units in the next couple of week.
https://github.com/AlexKlimaj/LiPow-Firmware