Neat project, some things that may be worth considering to solve the power issue:
- Use an ESP32-S3 to compare the initial still images, this could decide whether to wake the SBC for power hungry processing.
- Use PIR / mmWave to detect the motion then wake the SBC from sleep (they may not have the required range though)
- If not already, put everything to deep sleep when the light level is too low for good imaging.
- Move to LiFePo4 Lithium batteries.