A modular electric storage battery is adaptable to a variety of applications, and for example, as a starting, lighting and ignition (SLI) battery of a car, truck, motorcycle, lawn and garden equipment or other internal combustion engine powered product. The modular battery is constructed from a plurality of battery cells assembled into a battery housing. The cells are sealed, maintenance-free, rechargeable cells. The housing includes quick connect termination, and the starting application is adapted with a base unit having complementary termination. The modular battery and base unit also include aligning features to ensure proper interconnection of the battery terminals. The base unit may be adapted to receive several sizes of modular battery. In addition, a second modular battery, that may be configured as a flashlight or other device, is provided and can inter-connected with the base unit to provide a jump starting capability.