Something to be aware of when using metal cases of any kind to house the cells. The cell is wrapped with PVC material. Underneath is the aluminum case for the cell. The aluminum case is positive. So if something on the metal case the cells are housed in pierces the PVC and makes contact with the aluminum cell case, the metal case will become positive. And if the metal case makes contact with ground that will not be good unless the case is kept isolated from ground, as well as anything mounted to it that might have ground connected through a screw or something.