Got the battery from Goldenmotor, where the motor also are from...
35km range would be with no pedaling at all, and the 'pedal to the metal' (throttle at max)

; with a little pedaling in the steepest hills, the range extends to 40km+. I've yet to test the range with mostly pedaling, and using the motor just to assist; having way too much fun motoring...

You didn't mention your motors power? (Mine are 750W...)
A 10Ah battery would have lower 'max continuous amp' delivery capabilities than a 16Ah one, so that would probably limit your max speed if your motor are similar to mine...