A fully integrated electrical energy storage system that includes a battery management system (BMS) having advanced energy storage batteries with proprietary controls, switchgear, hardware and software monitoring using several platforms (e.g., Linux, Modbus, MOSFIT) inside a housing with built-in DC and AC disconnects, power distribution for both AC and DC power, components, wiring and proprietary bus bars that couple the batteries for power distribution, for charging and discharging to an external source, allowing external coupled power conversion systems to be easily and seamlessly integrated and connected; a battery management system (BMS) that includes rechargeable electrical energy storage batteries, an enclosure that houses the electrical energy storage batteries, power distribution components with wiring in the enclosure for coupling the batteries to an external circuit, and electronic control circuitry; an enclosure that houses electrical energy storage batteries as part of a battery management system (BMS); power distribution components with wiring in an enclosure for coupling batteries in the enclosure to an external circuit as part of a battery management system (BMS); electronic control components within an enclosure as part of a battery management system (BMS)