Abstract: An intelligent battery system and methods for making and using the same are provided. The intelligent battery system can halve a pack of cells and a battery management system. (“BMS”) for providing secondary protection for the pack of cells. The pack of cells can comprise cells with operating parameters such as capacities, voltages, currents, charge/discharge rates and/or lifecycles that are uniform, or different, among the cells. The BMS can comprise a gas gauge, a microcontroller and a MOS switch circuit for managing the pack of cells and providing the secondary protection based on chemical characteristics of the cells and operating parameters of the cells. The intelligent battery system advantageously can include cells that are replaceable. For purposes of storage and/or transportation an of the cells can be dissembled and assembled without affecting the capacity and performance of the intelligent battery.