In the early years, we used to mount the battery in the nose of the Challengers. After taking a close look at several weight and balance sheets, I discovered that the planes were actually in the forward portion of the envelope. With the Challenger II, your CG shifts further forward as you burn off fuel. Although the planes appeared to fly fine, I discovered that locating the battery more aft in the envelope produced better flying qualities. By balancing the plane more precisely, we rotate sooner and climb out faster. The underseat battery mount also made it easier to maintain with the new factory aluminum seats. By simply removing a couple bolts, the seat can be pivoted upright to give easy access to the battery. The batteries we use are totally sealed lead acid in a glass mat matrix which means they can be mounted in any position without fear of leakage.

In order to give the battery extra clearance from the elevator pushrod beneath it, I raised the seat an additional one inch to give plenty of room for full actuation ot the joystick without interference. A side benefit of raising the rear seat on a Challenger II is that you can see over the shoulder of the person in front.

The battery holding braces are made of simple 1/8" aluminum strapping material with aluminum angles riveted to them. You will need to measure the height and width of your battery for proper attachment of the aluminum angles. Then the aluminum straps are bent slightly at this measurement "plus" the width of the aluminum angles to allow the straps to rest on and bend around the aluminum seat tubes.