jotto wrote: I don't think the controller is fried though -- it still works with the SLA batteries and with 6S lipos.
Have you tried 7S?
It sounds like your controller can detect too high voltage and prevent power from going to the motor. I have seen this behavior with two wheelchair controllers. They both run on 24V SLA. I swap the SLA with a 6S (25.2V max) and they work fine. Also worked fine with 7S (29.4V max), but would not work with 8S (33.6V max). So I partially discharged the 8S pack until the voltage hit 30.0V and it worked.
No, I haven't tried 7S. I don't have the batteries to make that configuration. The overvoltage detection theory makes sense, though. This is a brand new E300, so perhaps they started adding overvoltage detection in the newer revisions.
Seems like a 36V controller is the way to go. Can the tnc scooter throttle controls be used on a brusless controller? I'm planning to convert to brushless some time in the future. For this season, I will stick to the stock motor.