Insane,
There really isn't a "normal" place to put the battery in a plane. Since it's used a tool to help balance the plane where it is placed will vary from plane to plane. I've had planes that had the batter directly behind the firewall, and I've had planes that had the battery installed at the end of the fuselage in the tail. Just as long as you secure the battery pack so that it can't move while in flight you'll be fine wherever you put the pack at. Just remember, no matter where you move the pack to it's still better than adding "dead" weight to a plane to balance it.

Hope this helps

Ken