An apparatus and battery system are disclosed. The apparatus includes a first panel, a first bus bar, and a second panel. The first panel includes a first upper surface and a first lower surface. The first upper surface includes a first cavity extending into the first upper surface towards the first lower surface. The first bus bar is within the first cavity. The second panel has a second lower surface in direct contact with the first upper surface. The second lower surface extends over a substantial portion of the first cavity.