Abstract: The invention concerns single and multiple cell lithium ion batteries. Embodiments of the invention concern single and multiple cell lithium ion batteries with built-in controllers that monitor the cell or cells and provide a safety disconnect when certain monitored conditions are detected by the controller. Preferred embodiment single and multiple cell lithium ion batteries have their cell or cells within a container having a positive terminal and a negative terminal. The built-in controller monitors the cell or cell for each of the following conditions: over temperature, short-circuit, overcharge, and over-discharge and the controller provides a safety disconnect when one of the monitored conditions exist.