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 R 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 Crate 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. INDEX TERMS Li-ion battery, reliability, iPhone battery, chemical aging, manufacturing defects, Crates .
Derating is widely applied to electronic components and products to ensure or extend their operational life for the targeted application. However, there are currently no derating guidelines for Li-ion batteries. This paper presents derating methodology and guidelines for Li-ion batteries using temperature, discharge C-rate, charge C-rate, charge cut-off current, charge cut-off voltage, and state of charge (SOC) stress factors to reduce the rate of capacity loss and extend battery calendar life and cycle life. Experimental battery degradation data from our testing and the literature have been reviewed to demonstrate the role of stress factors in battery degradation and derating for two widely used Li-ion batteries: graphite/LiCoO2 (LCO) and graphite/LiFePO4 (LFP). Derating factors have been computed based on the battery capacity loss to quantitatively evaluate the derating effects of the stress factors and identify the significant factors for battery derating.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.