POWER SUPPLY SYSTEM

A DC energy storage unit with a plurality of energy storage modules, each energy storage module including a plurality of electrochemical energy storage devices electrically connected in series; an internal control unit in the energy storage module; a power supply for the internal control unit; and a wireless communication system; wherein the total voltage of the plurality of energy storage devices in series is greater than or equal to 40 V DC, wherein the plurality of energy storage modules are coupled together in series, or in parallel, each energy storage unit including a wireless gateway for communication between the energy storage unit controller and each energy storage module; wherein each energy storage module further has a housing, the housing at least partially having a non magnetic material.