Abstract: Traditional vehicle battery management systems are often bulky, costly, and feature-overloaded, making them ill-suited for com pact applications.This paper presents the design of a compact, low-cost battery management system centered around an STM32 microcontroller and a lithium-ion battery.The system integrates hardware for parameter acquisition, charge/discharge management, multi-dimensional protection, and temperature control, and incorporates software functionalities for State of Charge(SOC) estimation and MQTT cloud-based communication.Experimental results demonstrate that the system can monitor the battery"s terminal voltage, current, and temperature in real time, accurately detect faults such as overvoltage, undervoltage, short circuits, and overheating, and provide rapid protection in response.The system features stable dual-link Bluetooth and 4G communication, with its operating status displayed simultaneously on an OLED screen and a cloud platform.Overall, it meets the requirements for low-power, low-cost design and holds promising application prospects.