An energy storage module (30, 32) for an electric vehicle or hybrid electric vehicle (12). Multiple low-voltage storage batteries (36) disposed on a tray (60) and connected in parallel circuit relationship form a low-voltage battery bank. A DC-to-DC converter (42) has an input connected to the low-voltage battery bank and an output connected to a high-voltage energy storage bank (34). An AC-to-DC converter (40) is connected to the low-voltage battery bank for charging the low-voltage battery bank from a source of AC electricity (45).