If anyone returns to this thread, I threw together a new version of the driver, which seems to work currently. I used it in this recipe:
https://community.home-assistant.io/t/recipe-esphome-adafruit-feather-esp32-s2-thinkink-e-paper-display-battery-monitor/
tl;dr:
external_components:
- source: github://Option-Zero/esphome-components@max17048
components: [max17048]
sensor:
- platform: max17048
battery_voltage:
name: Battery voltage
battery_level:
name: Battery level
rate:
name: Battery discharge rate
Lmk if you have success with this @lboue .