So the cord I linked above works perfectly for the Hamuti chicken coop door. There are others of longer length, but make sure they have the connections as the one I linked. DO NOT use the Renogy red and black cord mentioned near the top.
I have same door opener. 2 things:
1. I wouldn't use the cords recommended here. They don't look like the same pin connections. I am going to try this: https://www.amazon.com/Solar-Extension-Cable-Waterproof-Spotlights/dp/B07CTM1JLS/ref=asc
I'll advise if it works.
2. The damn chicken door is...