Seeed studio motor shield

Hey, I have the seeed studio motor shield and it seems to be working fine with small dc motors. But when I try to use a little more powerful motor like a 9v, the motor doesn't spin but only makes a humming sound. I believe it's because there isn't enough power being supplied but I've hooked it up to a 7v battery which is more than enough. Do any of you now how to fix this?

Seven volts doesn't seem like enough for a nine volt motor.

But when the battery is connected directly to the motor the motor goes fine

If that is the case, either it's hooked up wrong, or the software isn't right.

What about showing us:

  1. your schematics
  2. your sketch to drive the motor?