System safety and ISO 26262 compliance for automotive lithium-ion batteries

Lithium ion batteries pave the way for today´s plug-in hybrid and electric vehicles. However, these batteries contain the potential of thermal runaway, posing a higher safety risk from thermal incidences than NiMH batteries. Thermal runaway can be mitigated using electronic control systems, which are intended to maintain a safe state of the battery under all operating conditions. When safety depends on these control systems, any malfunction of the system or its elements (such as sensors, microcontrollers, contactors, software, etc.) may lead to a dangerous state. The newly published ISO 26262 standard provides processes and methods for the proper design, development and manufacturing of E/E automotive systems to ensure functional safety. In this paper, the ISO 26262 standard is applied to several example scenarios involving lithium-ion batteries for plug-in vehicles. Key concepts are explored and conclusions drawn regarding several of the standard´s required processes, including hazard analysis and risk assessment, functional safety concept, functional safety and technical safety requirements, and related topics.