Adafruit Motorshield external power maximum?

Hey,

Does anyone know what the maximum voltage is that you can apply to the external power block of the Adafruit Motorshield?

I've got two 9v batteries wired in series for a combined 18.2v, will this work or fry my shield?

What does the adafruit product page say?

Use a NiHm battery pack. They didn't even specify voltage.

Says 13.5V for the h-bridges here

9V batteries are never going to be able to produce enough current for motors in the first place.

Use an SLA or LiPo battery for good current handling.