Master thesis presentation Erik Brusewitz, MPPHS

Abstract: As the demand for energy storage systems continues to grow, lithium-ion batteries have emerged as a leading technology due to their high energy density, long cycle life, and lightweight properties. These batteries deteriorate as time passes, so evaluating and defining their degradation becomes a central part in ensuring safe operation and extension of battery lifespan. In this work, an end-of-life model was defined, developed, and tested, with the purpose to assess the status of the battery and to output a percentage value disclosing how close the battery pack is to its expiration. The model is split into three different sub-models: state of performance, state of safety and quality capping factors, each of which are further split into several metrics. Each metric is observing different battery behavior, and is made to be easily enabled or disabled to simplify a future implementation into a battery management system. The model can be calibrated with several parameter values, making it highly adjustable to any type of battery system. After development was concluded, Simulink simulations were conducted to ensure accurate model behavior. This was carried out with data collected from both the field as well as from cycled cells in a lab in order to assess a wide array of scenarios. The model is primarily built and optimized for use in Husqvarnas robotic lawn mowers, but can easily be implemented in most battery systems.

Examiner: Patrik Johansson
Supervisors: Kasper Westman, Imene Mansour & Anders Gidoff
Opponent: Sofia Reiner