This invention includes a hybrid housing for rechargeable battery packs. The housing utilizes thin metal sidewalls with overlaid plastic end walls by way of an insert molding process. In a single cell, lithium-ion application, the resultant battery pack is 4.9% smaller by volume. Each sidewall up to 75% thinner than prior art sidewalls made by way of an injection molding process. The resultant battery housing is thinner and stronger than prior art housings.