A scalable intelligent power-supply system and method capable of powering a defined load for a specified period of time is disclosed and claimed. Multiple external AC and DC inputs supply power to the system if available and required. An internal DC input from a back-up energy source is on board. The back-up energy source is scalable by adding additional energy cartridges such as batteries in racks mounted within frames of the system. The AC and DC inputs (including the internal DC input) are controlled, measured, sensed, and converted by circuitry controlled by the microprocessor into multiple AC and/or DC outputs. A microprocessor manages power input to, within, and output from the system. The performance of a Lithium-ion batteries used to power an automobile can be determined on the basis individual battery packs or individual battery cells within the packs.