Key points of battery module and battery pack hierarchical structure design

Integrated design of battery cells

Physical fixed structure

Elastic buffer frame: The battery cells are wrapped with flexible materials such as elastic silicone pads and flame-retardant rubber strips and then embedded in a metal frame. This design can absorb the slight expansion deformation (about 1% - 3% volume change) of the battery during charge and discharge cycles, avoiding internal structure damage caused by hard squeezing. For instance, during the frequent acceleration and deceleration of electric vehicles, the battery pack will be impacted by inertial forces. The elastic frame can disperse the stress and protect the battery.

Snap-fit splicing structure: Adjacent battery cells are connected by plastic clips with barbs, which can be quickly assembled and disassembled. Compared with traditional welding or bonding methods, this structure does not require damage to the battery pack structure during maintenance, and faulty cells can be replaced separately, reducing maintenance costs.

Thermal management channel

Microchannel heat sink: An aluminum alloy heat sink with microchannels is adhered to the surface of a single battery cell. The channel diameter is controlled at 0.5-1 millimeter, and the interior is filled with phase change material with a high thermal conductivity (greater than 2W/m·K). When the battery temperature rises, the phase change material absorbs heat and undergoes a phase change, rapidly transferring the heat to the surface of the heat sink, and then dissipating it through an external air cooling or liquid cooling system.

Three-dimensional air duct layout: Inside the battery module, "S" -shaped or "回" -shaped three-dimensional air ducts are designed, with a width of 5 to 10 millimeters, ensuring that air can flow evenly through the surface of each battery cell. According to the experimental data, a reasonably designed three-dimensional air duct can keep the temperature difference of the battery pack within 3℃, effectively improving the consistency and service life of the battery pack.

Battery module packaging design

Detachable sealing cover plate

Sealing structure: A sealing method combining silicone rubber sealing rings and metal cover plates is adopted. The cover plate is connected to the module housing through bolts, and the tightening torque of the bolts is controlled within 10-15 N·m. This structure not only ensures the internal sealing of the module (with a protection level reaching IP67), but also enables the cover plate to be quickly opened for internal inspection and maintenance when necessary.

Observation window: A transparent organic glass observation window is set on the cover plate, with the window area accounting for 10% to 15% of the cover plate area. Through the observation window, maintenance personnel can directly inspect the appearance of the battery cells, such as whether there are bulges or leaks, without disassembling the entire module.

Electrical connection design between modules

Quick-plug interface: The electrical connection between battery modules adopts aviation plugs with self-locking function. The contact resistance between the plug and the socket is less than 0.5mΩ, and the number of plugging and unplugging cycles can reach more than 500 times. During the maintenance process, simply unplug the plug to disconnect the electrical connection between the modules, making it convenient to inspect and replace individual modules.

Wiring harness arrangement bracket: A wiring harness arrangement bracket is set up inside the module to fix the electrical connection wiring harnesses on the bracket, preventing the wiring harnesses from loosening or interfering with other components. Meanwhile, clear numbers and functional identifiers should be marked on the wiring harness to facilitate maintenance personnel to quickly identify and troubleshoot faults.

Key points of Battery Management System (BMS) and electrical connection design

BMS hardware layout

Modular design: The BMS is divided into multiple independent modules such as the data acquisition module, control module, and communication module, and each module is connected through standardized interfaces. This design makes it convenient to replace a certain module separately when it malfunctions, reducing maintenance time and costs. For instance, when the data acquisition module malfunctions, only that module needs to be replaced instead of the entire BMS.

Heat dissipation and protection design: The BMS motherboard adopts a multi-layer PCB design. The surfaces of key components are covered with heat dissipation grease and heat sinks to ensure stable operation within the working temperature range (typically -20℃ to 60℃). Meanwhile, the BMS housing is made of dust-proof, water-proof and moisture-proof materials, with a protection level reaching IP65. to prevent damage to the BMS caused by external environmental factors.

Electrical connection optimization

Redundant design: Redundant design is adopted at key electrical connection points (such as the connection between the positive and negative terminals of the battery and the BMS, the communication lines between the BMS and external devices, etc.), that is, two or more connection lines are set up. When one of the lines fails, the other line can still ensure the normal operation of the system and improve the reliability of the system.

Identification and positioning design: Clear identification should be set up at the electrical connection harness and interface, including information such as the harness number, function, and connection direction. Meanwhile, in the layout of the wiring harness, color distinction or fixed direction is adopted to facilitate maintenance personnel to quickly find the corresponding connection points during repair and reduce the possibility of misoperation.

Key points of battery pack enclosure and safety protection design

Shell structure design

Lightweight and high-strength materials: The battery pack casing is made of lightweight and high-strength materials such as aluminum alloy and carbon fiber reinforced composite materials, ensuring the strength of the casing while reducing the overall weight of the battery pack. For example, the density of the aluminum alloy shell is approximately one-third that of steel, but its strength can meet the protection requirements of the battery pack.

Quick disassembly and assembly structure: The shell adopts a split design and can be quickly assembled and disassembled by means of clips, bolts, etc. Sealing strips are set at the connection parts of the shell to ensure the sealing performance after assembly. During maintenance, simply open the corresponding casing part to operate the internal battery module and BMS without disassembling the entire casing.

Safety protection design

Multi-level safety protection devices: The battery pack is equipped with multiple levels of safety protection devices such as fuses, circuit breakers, temperature sensors, and smoke sensors inside. When the battery experiences abnormal conditions such as overcharging, overdischarging, short circuit or overheating, the corresponding protective devices will act promptly to cut off the circuit or issue an alarm signal to prevent the accident from escalating.

Fuse selection: Based on the rated current and short-circuit current of the battery pack, choose the appropriate rated current and breaking capacity of the fuse. For example, for a battery pack with a rated current of 100A, a fuse with a rated current of 125A and a breaking capacity of 10kA can be selected.

Temperature sensor layout: Multiple temperature sensors are evenly arranged inside the battery module to monitor the battery temperature in real time. When the temperature exceeds the set threshold (such as 60℃), the BMS will activate the cooling system or reduce the charging current to ensure that the battery temperature remains within a safe range.

Pressure relief and fire extinguishing design: Install a pressure relief valve and a fire extinguishing device on the battery pack casing. When the internal pressure of the battery is too high or a fire occurs, the pressure relief valve will automatically open to release the internal pressure and prevent the battery from exploding. The fire extinguishing device will spray fire extinguishing agent to quickly put out the fire. For instance, the use of heptafluoropropane fire extinguishing agent has a high fire extinguishing efficiency and a small impact on the environment.