Arrays of planar solid state batteries are stacked in an aligned arrangement for subsequent separation into individual battery stacks. Prior to stacking, a redistribution layer (RDL) is formed over a surface of each wafer that contains an array; each RDL includes first and second groups of conductive traces, each of the first extending laterally from a corresponding positive battery contact, and each of the second extending laterally from a corresponding negative battery contact. Conductive vias, formed before or after stacking, ultimately couple together corresponding contacts of aligned batteries. If before, each via extends through a corresponding battery contact of each wafer and is coupled to a corresponding conductive layer that is included in another RDL formed over an opposite surface of each wafer. If after, each via extends through corresponding aligned conductive traces and, upon separation of individual battery stacks, becomes an exposed conductive channel of a corresponding battery stack.