Volts & amps: understanding motor ratings

[clanger9]

I’ve been juggling motor/battery combinations for my bike project and I’m a bit confused about how some of these Chinese motors are rated & designed.

e.g. this one: http://freerchobby.cc/e_productshow/?16 ... ar-16.html

Optimistic specs aside, it should be good for 75Nm starting torque and ~30kW continuous output, right? And with a 25KV/120V winding, it should spin up to 3000RPM. Yes?

So why do they recommend “22s” (i.e. 85V) battery pack and a 500A controller? Surely a 30s (120V) battery pack supplying up to 350A would be better?

I’m struggling to understand why they’d encourage you to run lower than the rated voltage.

Given that these OEMs try to present their products with the most flattering specs possible (within the bounds of legality), does this imply you can’t actually run this motor at 120V?

What have I missed?

[arber333]

What have I missed?

Well I think 85V inverter is much cheaper since it can use 120V mosfets. 120V would require 160V mosfets which are much more expensive. I think it is just the expense not so much in performance. Though you can revv better with higher voltage.

A

[clanger9]

Ah, I hadn’t thought about the inverter voltage rating. Makes sense, thank you!