I don't think you will get that much of an increase in range by boosting the battery count. You must keep in mind that there are resistors meant to keep you from running too much power, and by adding batteries, you'll probably smoke them, and the rest of your controller board as well. And then you'll end up walking 200 feet to get your bit cuz your controller smells like melted plastic.

Cliff notes: not a safe mod, you're better off settling for 30 feet of range with some easy mods than buying a new car cuz you feel the need to drive across the gym floor.