ESTIMATION OF THERMAL STATE OF CHARGE FOR PCC BASED LITHIUM-ION BATTERY PACKS
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With continuing efforts to improve energy and power density of Li-ion batteries, heat generation and thermal safety remain critical barriers to commercial success. Energy conversion in a battery is an exothermic process. Whenever the temperature of lithium-ion batteries increases, there can be direct consequences-reduced calendar and cycle life and higher risk of a battery re or explosion. Conventional approaches to prevent overheating use active thermal management systems, such as air conditioning or liquid cooling. However, these systems can be costly, bulky, and consume energy during operation. In addition they o er no overheat protection while the application or the vehicle is powered down. Phase change material composites (PCC) can be employed to rapidly absorb heat from the battery and distribute it, thereby enabling lightweight and compact packs with extended cycle-life and safety. This thesis proposes an online temperature estimation technique for a novel intelligent battery thermal management to actively monitor thermal mass of the phase change material. Such a system will not only enable avoidance of thermal issues, but will extend life of the battery pack by optimally selecting the operating point of the Energy Storage System. It can also be used to predict when active cooling should be employed just before the battery exits the phase change temperature plateau, to ensure latent heat absorption is spread across the entire drive cycle.