Abstract: A very large number of small electric cells are assembled electrically in parallel into a cell module to provide a large ampere-hour capacity and, in turn, multiple cell modules are series connected into a spacecraft battery having the power necessary to satisfy the requirement of the spacecraft. The invention provides for (a) three-dimensional packaging of parallel cells, (b) rejecting the internal heat from such a package, and (c) providing redundant electrical fuse protection for the internal cell array. Thus, at least first and second layers are provided, each being of plural commonly aligned, parallel bussed, electric cells, each cell including opposed ends and an outer peripheral surface. The cells are disposed in a planar side-by-side relationship, and each layer includes a plurality of outermost cells encompassing an interior region. The layers are connected electrically in parallel and are laterally coextensive and aligned in an end-to-end relationship.