Design ideas for the installation structure of lithium battery pack BMS

First, clarify user needs and core goals

User Demand Insight

Safety requirements: Users hope that the BMS can monitor the battery status in real time, promptly handle abnormal situations such as overcharging, overdischarging, overcurrent, and short circuit, prevent battery thermal runaway, fire or explosion, and ensure the safety of personnel and equipment.

Performance optimization requirements: It is expected that the BMS can accurately estimate the SOC (State of Charge) and SOH (State of Health) of the battery, rationally allocate the charging and discharging current, extend the battery's service life, and improve the overall performance of the battery pack.

Reliability and stability requirements: It is required that the BMS can operate stably in various harsh environments (such as high temperature, low temperature, high humidity, strong vibration, etc.) to ensure the normal operation of the battery pack and reduce the probability of faults.

Maintainability requirements: Facilitate the installation, commissioning, maintenance and upgrade of the BMS to reduce maintenance costs and time.

Core goal setting

Design a compact and reasonable installation structure: enabling the BMS to be stably installed inside the lithium battery pack while minimizing the impact on the space and weight of the battery pack.

Ensure good electromagnetic compatibility: Avoid electromagnetic interference between the BMS and other electronic components inside the battery pack to guarantee the accuracy and stability of signal transmission.

Provide effective heat dissipation channels: Prevent the BMS from being damaged due to overheating during operation, and enhance its reliability and service life.

Second, selection of installation location

Close to the central area of the battery pack

Advantage: The temperature in this area is relatively uniform, which can reduce the impact of the internal temperature gradient of the battery pack on the measurement accuracy of the BMS. For instance, in large energy storage battery packs, installing the BMS close to the center of the battery pack enables the BMS to more accurately sense the overall temperature changes of the battery pack, thereby better controlling the charging and discharging processes.

Note: It is necessary to ensure that the installation position does not block the heat dissipation channels of the battery pack to avoid affecting the overall heat dissipation effect of the battery pack.

Convenient for electrical connection

Principle: Select a position that is closer to the battery cells and the main circuit to reduce the length of the connecting wires, lower the line resistance and voltage drop, and enhance the efficiency and quality of signal transmission. For instance, in the battery pack of an electric vehicle, installing the BMS near the battery modules enables convenient electrical connection with individual battery cells and real-time collection of information such as the battery's voltage, current and temperature.

Considerations: At the same time, it is necessary to avoid interference between the connecting wires and other components inside the battery pack to prevent wire wear or short circuits.

Third, fixed method design

Mechanical fixation

Bracket fixation: Design a dedicated BMS installation bracket. The bracket should have sufficient strength and rigidity to withstand the weight of the BMS and the vibration and shock generated during vehicle operation or equipment running. The bracket can be fixed to the outer shell or internal structure of the battery pack through fasteners such as bolts and screws. For instance, in industrial energy storage battery packs, metal brackets are used to firmly fix the BMS on one side of the battery pack to ensure that it does not loosen during long-term use.

Snap fixation: For some small or lightweight BMS, the snap fixation method can be adopted. The buckle design should be simple and reliable, easy to install and disassemble, and at the same time ensure that the BMS does not shake after installation. For instance, in the battery packs of portable electronic devices, plastic clips are used to fix the BMS inside the battery pack, which not only facilitates production and assembly but also makes later maintenance easier.

Shockproof design

Buffer material application: Install buffer materials such as rubber pads or sponge between the BMS and the fixed bracket or battery pack to absorb and buffer vibration energy and reduce the impact of vibration on the BMS. For instance, in the battery pack of an electric bicycle, placing rubber pads at the bottom and around the BMS can effectively reduce the impact of vibrations generated during vehicle operation on the electronic components inside the BMS.

Optimization of shock absorption structure: Design a reasonable shock absorption structure, such as using spring shock absorption, damping shock absorption and other methods, to further enhance the seismic performance of BMS. For instance, in some special application scenarios with high requirements for vibration, dedicated shock absorption devices can be designed for BMS. Through the combined effect of springs and dampers, the vibration amplitude can be reduced to the minimum.

Fourth, electrical connection design

Wire selection

Specification matching: Select the appropriate specification of wires based on the input and output current and voltage requirements of the BMS. The cross-sectional area of the wire should be large enough to reduce the line resistance, minimize energy loss and heat generation. For instance, for battery packs with high current charging and discharging, wires with larger cross-sectional areas should be selected, such as 4mm², 6mm², etc.

Insulation performance: The wire should have excellent insulation performance, capable of withstanding the working voltage of the battery pack and environmental conditions, and preventing leakage and short circuit accidents. Meanwhile, the insulation layer of the wire should have certain properties such as temperature resistance, moisture resistance and corrosion resistance.

Connection method

Welding connection: For some electrical connection points with high requirements for connection reliability, welding can be adopted. Welding connection has the advantages of firm connection and low resistance, but it requires professional welding equipment and operational skills. For instance, the voltage sampling line between the BMS and the individual battery cells can be connected by welding to ensure the stability of signal transmission.

Plug-in connection: To facilitate installation and maintenance, some electrical connections can be made by plug-in method. The plug-in parts should have good contact performance and insertion and extraction service life. At the same time, it is necessary to prevent the plug-in parts from loosening during vibration or use. For instance, the communication interface between the BMS and external devices can adopt standardized connectors, facilitating quick connection and disconnection.

Wiring harness arrangement

Reasonable layout: The electrical connection wiring harnesses of the BMS should be arranged reasonably to avoid crossing, entanglement and excessive density of the wiring harnesses. The wiring harness can be fixed inside the battery pack by using wire troughs, wire clamps and other fasteners, making the wiring harness neat and orderly. For instance, dedicated cable trays can be set up inside the battery pack, with different functional wire harnesses placed in separate trays to facilitate installation and maintenance.

Clear identification: Make proper markings on the wiring harness, indicating the connection objects and functions of the wiring harness to facilitate quick identification and operation during installation, commissioning and maintenance. For example, use wires of different colors or stick labels on the wire harness to distinguish different signal lines from power lines.

Fifth, electromagnetic compatibility design

Shielding design

Metal enclosure shielding: Metal enclosures, such as aluminum alloy enclosures, are designed for BMS to shield against electromagnetic interference. The metal casing should have good grounding performance to introduce interfering signals into the ground. For instance, in the battery pack BMS of the industrial control field, the use of an aluminum alloy casing can effectively shield the influence of external electromagnetic radiation on the internal circuits of the BMS.

Shielded wire application: For some signal lines that are sensitive to electromagnetic interference, such as communication lines and sensor signal lines, shielded wires are used for connection. The shielding layer of the shielded wire should be reliably connected to the metal casing or grounding end of the BMS to ensure the shielding effect.

Filtering design

Power filtering: Install a filter at the power input end of the BMS to filter out high-frequency noise and interference signals in the power supply, ensuring a stable power supply for the BMS. For instance, the use of π -type filters or EMI filters can effectively suppress electromagnetic interference in the power supply.

Signal filtering: For sensitive signals within the BMS, such as analog signals and digital signals, filtering circuits can also be used for filtering processing to enhance the quality and anti-interference capability of the signals. For example, adding a low-pass filter to the voltage sampling circuit can filter out the high-frequency noise in the sampled signal.

Sixth, heat dissipation design

Natural heat dissipation

Heat dissipation channel design: In the BMS installation structure, design a reasonable heat dissipation channel to allow the air to circulate freely and carry away the heat generated by the BMS. For instance, set up heat dissipation holes or grooves around the BMS to increase the convection area of the air.

Selection of heat dissipation materials: Choose materials with good heat dissipation performance to make the shell or heat dissipation components of the BMS, such as aluminum alloy, copper alloy, etc. These materials can quickly conduct the heat inside the BMS to the external environment.

Forced heat dissipation

Fan cooling: For BMS with high heat generation, fans can be installed for forced cooling. The selection of fans should be reasonably matched based on the heat dissipation requirements of the BMS and the installation space to ensure that the fans can provide sufficient air volume and air pressure. For instance, in some high-performance electric vehicle battery pack BMS, the use of small cooling fans can effectively reduce the operating temperature of the BMS.

Heat sink cooling: Install heat sinks on the key heat-generating components of the BMS to increase the heat dissipation area and improve the heat dissipation efficiency. The material and structure of the heat sink should be designed according to the characteristics of the heat-generating components to achieve the best heat dissipation effect. For instance, installing heat sinks on the power tubes of BMS can effectively reduce the operating temperature of the power tubes, enhance their reliability and service life.