Well, it ran for 22 minutes, until the voltage on the battery dropped to 10.2ish. 90% of that is about the 9.5v I observed earlier where it turned off. After a couple minutes for the battery to temporarily recover it started right back up (albeit with the voltage dropping quickly).

I was going to do some more research on the controller itself, and then try some different frequencies and see if I can make anything work.

Otherwise, it looks like the controller will be just be an on/off deal, driving the fan at 90%.