Li-ion Battery Reliability – A Case Study of the Apple iPhone®

Li-ion battery reliability has attracted significant research attention, but few studies have incorporated in-service performance and reliability data of batteries installed within a product. This paper investigates battery drain, unexpected shutdowns, and slow performance associated with Li-ion batteries, with a focus on Apple iPhones
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as a case study. The actions taken by Apple in response to these performance issues are discussed, especially from the perspective of Li-ion battery degradation. It is shown that not all battery reliability issues can be attributed to normal battery degradation; battery manufacturing defects and high C-rate applications are also shown to be contributors to battery reliability and performance issues, including those causing a low state of charge, a low state of health, and unexpected shutdowns.