I believe if the battery cameras detect a constant power source then there should be an option to enable onvif/rtsp for battery cameras, I believe this can be achieved with an update for battery cameras. TP-Link should also make a outdoor power cable for battery cameras as well with a fitting that'll still block water from getting into the port. I have a smart plug currently hooked up to my tc82s so I can let the battery drain naturally and turn it on when I want and hooked up to a battery backup for just incase.

Model: TC82
Hardware: 1.0
Firm: 1.0.24