A Combined Health Estimation and Active Balancing Electronic System for the Life Enhancement of Batteries in Hybrid and/or All-Electric Propulsion Systems

NASA seeks intelligent monitoring for hybrid and/or all electric propulsion systems, as well as methods to significantly extend the life of electric aircraft propulsion energy sources and their safety. The requirement to advance towards more fuel efficient and environmentally friendly aircrafts demands battery systems that can operate for longer periods of time in a safer and more reliable manner. An attractive technique that can be used to increase battery pack life is that of active balancing. Active balancing is typically used to increase the amount of energy put into or extracted out of a battery. If performed efficiently and accurately, active balancing can translate into longer battery life and more efficient battery utilization. Active balancers presently equalize either voltage or State of Charge (SOC) in a group of cells or super-cells in series. The more accurate in-operando SOC active balancers depend on on-line SOC estimation algorithms that are typically based on terminal voltage, current, and temperature. These algorithms (e.g., Coulomb counting, Kalman-based filter estimation, etc) accumulate errors and/or become unstable as a consequence of measurement errors, model simplifications, and the lack of an accurate battery parameter determination and tracking method, which is critical as the battery ages and/or operates under unforeseen conditions. To assist with this problem we propose to develop an active balancing electronic system that can jointly balance the battery pack and measure battery health related parameters without additional hardware. We propose to use this efficient electronic system to demonstrate an improved active balancing system capable of battery life enhancement and safety operation. More »