In addition, the monitor can be used to prevent aging when batteries are being charged. He says, "Fast charging accelerates the aging of batteries. With this monitor, you can insure that you charge as fast as possible while minimizing aging."
Kozlowski will detail the use of the monitor to prevent battery aging in a paper, Condition Monitoring for Life Extension of Fast, High Density Battery Charging, to be presented, Friday, April 19 at the 56th annual Machinery Failure Prevention Technology meeting in Virginia Beach, Va. His co-authors are Todd A. Hay, former ARL staffer, Amulya K. Garga, ARL research associate, and Matthew J. Watson, former ARL staffer. The University has patented the monitor technology.
Kozlowski, who is conducting a comparative analysis of the new device as his doctoral dissertation, notes that most existing battery monitors use a very narrow spectrum of measurements and only tell the percent of charge. For example, the prompt on a laptop can say that the battery is 90 percent charged. However, depending upon the age and condition of the battery, 90 percent charge could mean two hours of working time for one battery and four hours for another. The PSU/ARL monitor takes the physical condition of the battery and its age or past history into account as well as the percent of charge. The result is highly accurate estimates of working time, physical condition and causes of failure based on a broad database. The first step in developing the new monitor was determining what could be measured. For example, physical changes on the electrode surfaces can only be measured directly when the battery is torn apart. Potential, current and temperature can be observed directly on the intact battery and can be used to deduce information about internal physical processes, just as taking a person's temperature can supply important information about their health. The team initially monitored terminal and cell voltages, load currents, surface and internal temperatures, and electrolyte pH but found the most informative measurements were electrical impedances across a broad band of frequencies.
"The idea of measuring impedance or what happens when you put a signal into a battery and then look at it when it comes out, has been around for a long time," Kozlowski says. "The signal that comes out is rich in information about the status of the battery. However, until recent advances in technology, measuring the small impedances was very difficult." Now, advances in technology coupled with ARL's signal processing, data fusion and automated reasoning innovations, have made the multi-functional monitor possible. The new monitor uses three automated reasoning methods, neural nets, fuzzy logic, and auto-regressive moving average, and a decision block to combine the three estimates into a final prediction. The Penn State researcher says the approach broadens the applicability of the monitor, since different reasoning methods perform better with different batteries, and enhances the reliability of the results. The monitor project is supported by grants from the Office of Naval Research