NASA seeks intelligent monitoring and control methods to significantly extend the life and improve the safety of hybrid-electric propulsion, all-electric propulsion, and other applications where energy storage sources are used, such as in satellites and aerospace aircrafts. Lithium-based batteries are increasingly being used in many aerospace applications due to their superior energy and power density. Most of these systems have standardized electric power buses, but batteries are frequently custom made to provide high performance, which incurs in a high cost. On the other hand modularity and distributed control of energy storage systems promise many advantages over these centralized and custom systems, such as reduced cost, increased reliability and fault tolerance, increased supplier availability, improved thermal management, and the possibility to efficiently interconnect heterogeneous, but complimentary, batteries to deliver energy efficiently under dynamic load scenarios. Performance however is a factor that must improve to make modular distributed systems even more attractive. We propose a distributed and modular technology that will allow NASA to create batteries by interconnecting smaller Lithium-based battery pack modules in a flexible and efficient manner while gaining in energy extraction performance. The proposed technology accomplishes this efficiently and regardless of specific chemistry in a master-less distributed way while minimizing size, weight, and using lower power electronic components when compared to conventional approaches. The interconnected battery system combines unique distributed algorithms with a hardware design that utilizes every pack efficiently regardless of specific chemistry. This is accomplished by a joint estimation and prediction approach that considers present battery state and future load dynamics. The result is an energy storage system with longer life and with all the attractiveness of a distributed and modular system.
Our proposed system has relevance in several NASA applications, such as Cube satellites, electrical systems in aircrafts, rovers, landers, habitats, and future planetary science missions. As a single, but detailed example, report JPL D-101146 highlights several needs that must be addressed within NASA missions. All point at the need for higher specific energy and operations under extreme temperatures, which can be better addressed through efficient modular and distributed systems.
Technologies as the one proposed are critical for renewable systems (solar, wind), and for transportation markets which are increasingly moving towards hybrid/electric vehicles. The military is also critically interested in modular energy storage systems due to higher fault-tolerance, one example is the U.S Army transition from Lead-acid to Lithium-based 6T battery modules for their entire fleet.