Keyword: ASPICE SYS.3, System Architectural Design, System Architecture, Client Architecture, Battery Management System, Lithium-Ion Battery, Li-Ion, Super Capacitor, SCAP, Energy Storage System, System Decomposition, Interface Design, Requirement Allocation, Functional Allocation, Hardware Software Partitioning, Logical Architecture, Physical Architecture, SysML, UML, MBSE, AUTOSAR, Functional Safety, Cybersecurity. Define system elements, subsystems, logical and physical architecture, interfaces, communication topology, operational modes, and allocation of requirements to hardware, software, mechanical, diagnostics, functional safety, and cybersecurity domains.