if you really want to know, look on ebay for the same motor you have, and you'll probably find one with a nameplate on it.
that said, the only treadmill motor i have is 120volt, 2520 rpm, which works out to 1900 at 90 volts, which is just about the same as all the others.
yes, you need a blocking diode to charge a battery and the current only starts flowing after the motor volts exceed the battery volts.