Okay, okay, that's enough!

You know I just got called Mcconaughey again the other day when I was out of town believe it or not!
If you want a battery suggestion, I would use the A123 15 or 20Ah prismatics, that is, if you weren't already thinking of using them.
http://www.cloudelectric.com/category_s/385.htm
There is a link to some DC motors that should work with a mower blade, there is a nice 24v 900watt unit that should be just right for the job, $150. IMO better than using a BL outrunner, all you need is a contactor, and probably more durable for sure, built for the type of duty.