[magnets]

the size of the batteries is not consistent between batteries, and can even bloat out sometimes. We've gotten a battery stuck in a wooden battery box once, and we could take it out with a rubber mallet. We had to take apart the robot. If you're building a battery box, make sure that whatever holds it on the side is adjustable, and that it's held down with some sort of strap, or something that can be ok with slight variations in height.