I just installed two twc gen3 and i wanted to use the power sharing mode. I live in Sweden (230V and main 20A fuse for the house. Both twc on 3x16A each). One twc on each side of the house. Unfortunately the didn’t connect to each other because they were to far away. I assumed that they use my home wifi for power sharing, but i was wrong…
I called Tesla and they told me that I hade to put them closer and a wifi extender won’t work.
But I bought a wifi extender anyways ans I got it working 
.
Maybe this will help someone else!
First I extended the “slave” twc, and started the powersharing connection through the “master” twc. And when the start to communicate the “slave” connects to the “master” twc. So I just extended the “master” twc afterwards. And it have been working since.
But whats already reported, the “slave” disconnects frome my home wifi and I can’t get any data to Home Assistant. Maybe some of you find a solution that gets data from the main twc?