This study investigates the effects of elevated temperature on commercially available high power graphite/LiFePO4 cells using a temperature dependent, electrolyte enhanced, single particle model (ESPM-T) coupled with a Solid Electrolyte Interphase (SEI) layer growth aging model. The ESPM-T is capable of simulating up to 25C and 10 sec charge-discharge pulses within a 35–65% SOC window and 25°C to 40°C temperature range with less than 1% voltage error, so it is suitable for hybrid electric vehicle (HEV) applications. The aging model is experimentally validated with an aggressive HEV cycle running for 4 months with less than 1% error. Instead of defining battery End of Life (EOL) as an arbitrary percent of capacity loss, we use the cycle number when the battery voltage hits 3.6V/2V (maximum/minimum) voltage limits. This is the practical limit of operation without reduced performance. Simulations show that operating cells at 35°C increases their life by 45% compared to room temperature operation. If the cell temperature is increased stepwise, then battery life is increased 85% more with a 50°C cell temperature at EOL. Battery initial size can be reduced by 24% using this temperature set-point strategy.
- Dynamic Systems and Control Division
Elevated Temperatures Can Extend the Life of Lithium Iron Phosphate Cells in Hybrid Electric Vehicles
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Tanim, TR, Rahn, CD, & Legnedahl, N. "Elevated Temperatures Can Extend the Life of Lithium Iron Phosphate Cells in Hybrid Electric Vehicles." Proceedings of the ASME 2015 Dynamic Systems and Control Conference. Volume 2: Diagnostics and Detection; Drilling; Dynamics and Control of Wind Energy Systems; Energy Harvesting; Estimation and Identification; Flexible and Smart Structure Control; Fuels Cells/Energy Storage; Human Robot Interaction; HVAC Building Energy Management; Industrial Applications; Intelligent Transportation Systems; Manufacturing; Mechatronics; Modelling and Validation; Motion and Vibration Control Applications. Columbus, Ohio, USA. October 28–30, 2015. V002T26A003. ASME. https://doi.org/10.1115/DSCC2015-9763
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