Well I'm not talking about the narrators credentials, or the whole gravity plane either, nor the practicality of it, but the simplified problem in post 11. Assuming you recapture most of the compression energy when you release it into the balloon, and capture energy in the windmill on ascent and descent, is it feasible that the battery would "never" drain completely with the right equipment?
The whole
FTTWDW debacle was eye opening enough that I don't want to dismiss it outright.