Due to increasing concerns with petroleum usage and the increasing federal fuel economy regulations, electric powertrains have become more accepted by automotive manufacturers. The lithium-ion batteries employed in such systems are typically managed by an electronic battery management system (BMS). The BMS manages the battery to prevent thermal runaway and related thermal events, and is responsible for safety related functions such as thermal management, cell balancing, and controlling the connection to the vehicle's high-voltage DC bus. The ISO 26262 standard, introduced in final form in 2011, provides a framework for developing and validating automotive products that are safe from electronic and electrical system malfunctions, including BMS malfunctions, in passenger vehicles. This paper discusses options for BMS system development in accordance with ISO 26262. Hazards and risks of BMS malfunctions are identified and classified according to the standard. A concept BMS system is then developed according to ISO 26262 methodologies, including system architectures, requirements at multiple levels, and hardware architectural metrics. Architectures for battery systems design are developed and discussed, and conclusions are drawn regarding critical tradeoffs in safe battery designs for hybrid and electric vehicle application.