Lithium-ion batteries are becoming essential vehicle components with the ongoing shift to electric vehicles. Battery management systems manage these batteries. Typically, battery management systems used to be placed deep within the vehicle architecture, away from external interfaces. However, with increasing connectivity to backend systems, e.g., to improve monitoring battery properties and optimize charging, battery management systems have moved closer to the attack surface, increasing security risks. Also, batteries will soon be reused in so-called second life applications, e.g., as an energy storage system in a private home. While conventional methods involve removing the battery and reusing it with a new battery management system, modern methods retain the original system. Though security controls exist for first and second life applications, there is a lack of research on the transition phase. This paper analyzes the phase of transferring the battery management system from the first to the second life of particular relevance for security, privacy, and intellectual property. We try to close this research gap by analyzing the security aspects of a battery management system life cycle and its altering system environment. We are defining the transition phase, identifying necessary activities, and providing cybersecurity needs for the transitioning of battery management systems from first to second life.