With the rapid development of urban low-voltage electric vehicles (EVs) in fields such as short-distance travelling and logistics and delivery, the issues of range and charging efficiency are becoming more and more evident. The traditional fixed charging method has limitations such as long charging time and high cost of infrastructure construction, which affects the user experience and market penetration. In this thesis, an innovative battery swap system is designed for the M1 class of urban passenger cars, represented by the Fiat 500e. The study transforms the original 400V high-voltage power architecture into a modular 48V low-voltage system, which improves safety while providing greater scenario compatibility for battery swap operations.