Battery Performance and Operation
Modeling and Simulation Tool
Under government funding, GAC has been developing a rechargeable Lithium – Ion (Li-Ion) battery performance and operation simulation tool that takes advantage of two state-of-the-art, University first-principles electrochemical models that have been developed over the last 20 years. GAC, along our research partner, NASA/JPL, has been incorporating, extending and validating the “Single Particle Model” (SPM) of Dr. Ralph White (University of South Carolina) and, together with Washington University, the “Reformulated Model” (RFM) of Dr. Venkat Subramanian. Both models have been incorporated into GAC’s Battery Performance and Operation Modeling and Simulation tool we call Dakota. With regard to the SPM, emphasis has been directed to the extension of higher rates and a wider range of temperatures. By itself, the SPM is much faster than the Full Physics Model (FPM) developed by Newman and others because of the simplifications that have been included in the SPM. The RFM that GAC and Dr. Subramanian have been incorporating into Dakota is focused on Low Earth Orbit (LEO) space mission model development for a variety of in-orbit operating conditions. The RFM, compared to the FPM, is much faster, handles higher charge and discharge rates, has the capability of operating over a wider range of temperatures and retains the fidelity of the FPM. In other words, once the RFM has been generated for a particular cell, the resultant simulations are as good as the FPM but with significantly reduced runtime. To date, GAC has incorporated and validated these two “simplified” first-principle models into Dakota for three different Li-Ion cell chemistries and manufacturers.
Papers presented at the 2009 NASA Battery Workshop
Papers presented at the 2010 Power Sources Conference
Aerospace Benefits of Modeling Tool
There are several potential benefits to the aerospace industry, especially to battery users, and power systems designers and developers as well as cell and battery manufacturers. The Dakota model has the potential to be used for a number of commercial applications where predicting life and performance is essential. The Dakota Battery Performance and Operation Modeling and Simulation tool has the capability of being used for:
- Li-Ion Cell and Battery Technology Acceptance
- Cell Design Parameter Selection for Mission Versatility
- Identification of Early Failure and Rundown
- Simulation of the Entire Operational Life of a Battery
- Monitor Batteries on Flight Missions, and
- Map and Simulate Manufacturing Processes
Li-Ion Cell and Battery Technology Acceptance. With the Dakota model, the projected use of Li-Ion cells and batteries in missions with long cycle and calendar life will be facilitated through proper simulation and demonstration of the technology. Without such a tool, the only alternative would be through real-time acceptance testing, which is time consuming and expensive. As is well recognized, the use of Li-Ion cells and batteries, in place of conventional alkaline systems, will significantly benefit satellite missions in terms of mass and volume savings.
Cell Design Parameter Selection for Mission Versatility. The development of Dakota will significantly help in the evaluation and selection of appropriate cell and battery design and size to meet the desired power capability, power and energy margins and life, as dictated by the LEO, GEO and other related aerospace operations. Also the Dakota tool is designed to incorporate basic cell design parameters such as plate thickness and material quantities so that the model can be extended to the design of the desired cell configuration, either prismatic, cylindrical or wound prismatic.
Identification of Early Failure and Rundown. A high-fidelity modeling tool could highlight the limitations for operational conditions that lead to early failure or accelerated rundown that limits mission life. It could also indicate the impact on performance of high pulse power on battery voltage levels during flight operations. For aerospace applications, the lifetime of a spacecraft is very important and extending cell and battery life is crucial.
Simulation of the Entire Operational Life of a Battery. Satellite program managers and their spacecraft and power systems engineers need a tool that enables them to make cell and battery choices based on projected life and performance in lieu of 5-10 year life testing in a laboratory. This would give users the opportunity to make cell and battery selection decisions based on shorter laboratory tests and simulated testing of the entire life of a battery. The users would also benefit from having a tool that will assist them in making power system design and operation decisions by being able to simulate various power management protocols, including extended ground storage and pulse power requirements, before the satellite is designed and built.
Monitor Batteries on Flight Missions. Satellite operations engineers and managers have need for a tool that enables them to simulate future battery usage and to predict the impact on the battery margins, health and life. This is especially useful when priorities for satellite services, and corresponding energy requirements, might possibly exceed battery capacity margins for continued healthful battery operation. In addition, such a tool could be useful in troubleshooting battery or power system problems arising during a mission.
Map and Simulate Manufacturing Processes. Because the Dakota Battery Performance and Operations Modeling and Simulation Tool is based on electrochemical first principles and cell design parameters, its predictions of cell and battery performance, especially after prolonged storage and cycling or unusual cell rundown or divergence, will help identify the criticality of the cell design and fabrication parameters on the performance. Recognition of manufacturing process changes could be identified when the test results do not mirror model output. It is thus possible to ensure cell robustness by focusing on these parameters during manufacturing.
Terrestrial Applications
Electric Vehicles and other Commercial Applications. An obvious application of Dakota is in modeling and simulation of Li-Ion batteries for electric vehicles and other applications where Li-Ion cell, battery and power systems performance prediction are desired in making important energy storage engineering and project decisions.
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Battery Health Monitoring System
A problem with critical-use batteries are that they typically replaced on a frequent cycle without regard to their actual quantitative condition and remaining useful life, which at present is very difficult to predict, especially for some newer battery chemistries, e.g. Li-Ion. Experts suspect that in normal use battery life could be up to twice as long as the replacement cycle, however, without a means to assess the remaining useful life, quantitatively, the battery is replaced on safety and reliability grounds e.g., the military. It is desirable to have technology that would allow one to predict the health of these batteries in the maintenance environment. This issue has become more acute with transition to aircraft that rely more on electrically-driven systems in critical subsystems, such as the new F-35 Lightning II fighter aircraft. Global Aerospace Corporation and its research partner, Jet Propulsion Laboratory, are developing system concepts that would enable one to determine and predict, in the maintenance environment, the health of Li-Ion batteries. If successful, this development could lead to improved safety and reliability and significantly reduced maintenance costs.
Such a system will address three specific needs, namely, (1) reduced maintenance costs by allowing the continued use of healthy batteries; (2) increased system safety and reliability, which is necessary for military missions and critical applications, and prevent complete battery discharge and destruction; and (3) reduced costs by eliminating need for battery removal for determining health diagnostics and prognostics. |
