Key points of multi-layer stacking structure design for lithium battery packs

First, safety design

Thermal management design

Heat dissipation channel planning: In a multi-layer stacked structure, the heat dissipation channels between batteries are crucial. Make sure there is sufficient gap between each layer of batteries so that air or coolant can flow smoothly. For instance, a 2-3mm gap can be set between two adjacent battery layers to form vertical or horizontal heat dissipation air ducts, enabling the heat to be dissipated in a timely manner.

Application of thermal conductive materials: High thermal conductivity materials such as thermal conductive silicone pads and graphite sheets are used between batteries and between batteries and structural components to enhance thermal conduction efficiency. Thermal conductive silicone pads can fill the tiny gaps between the battery and structural components, reducing thermal resistance and enabling the heat generated by the battery to be quickly transferred to the heat dissipation components.

Temperature monitoring and control: Install temperature sensors at key positions on each layer of batteries to monitor the temperature changes of the batteries in real time. When the temperature exceeds the set threshold, promptly activate the cooling system (such as fans, liquid cooling devices, etc.) to lower the temperature and prevent battery thermal runaway.

Electrical safety design

Insulation protection: Insulation treatment should be carried out at the electrical connection points between batteries and between batteries and structural components to prevent short circuits. Insulating tape, insulating sleeves and other materials can be used to wrap the connecting wires, and insulating gaskets can be placed between the battery and the metal structural components.

Overcurrent protection: Install overcurrent protection devices such as fuses and circuit breakers in the charging and discharging circuits of the battery pack. When the current exceeds the rated value, the protective device can quickly cut off the circuit to prevent the battery from being damaged due to overcurrent or causing safety accidents.

Explosion-proof design: The battery casing should have certain explosion-proof performance to be able to release pressure in a timely manner when the internal pressure of the battery abnormally rises. Explosion-proof valves and other structures can be adopted. When the pressure reaches a certain value, the explosion-proof valve will automatically open to release the internal pressure and prevent battery explosion.

Second, structural stability design

Selection of stacking method

Alignment and stacking: Align and stack the batteries in a unified direction and position to ensure the stability of the center of gravity of each layer of batteries. This stacking method is convenient for installation and fixation, and can reduce the displacement of the battery pack under vibration or impact. For instance, in the battery packs of electric vehicles, the alignment and stacking method is usually adopted to make the overall structure of the battery pack compact and stable.

Interlaced stacking: In some cases, to enhance the structural strength of the battery pack or improve heat dissipation, an interlaced stacking method can be adopted. That is, the arrangement directions of two adjacent layers of batteries are interlaced with each other, forming a certain support structure. However, interlaced stacking will increase the difficulty of installation and wiring, and a reasonable design is required.

Fixation and connection methods

End plate and side plate fixation: Install end plates and side plates at both ends and on both sides of the battery pack, and fix the batteries together by means of bolts, welding, etc. The end plates and side plates should have sufficient strength and rigidity to withstand the weight of the battery pack and external forces. For example, aluminum alloy end plates and side plates are used to fasten the battery pack into a whole through high-strength bolts.

Battery connection: The electrical connection between batteries should be firm and reliable, and appropriate connection methods should be adopted, such as welding, bolt connection, etc. The connection parts should be insulated to prevent short circuits. Meanwhile, it is necessary to ensure that the connection resistance is as small as possible to reduce energy loss and heat generation.

Buffering and shock absorption design

Buffer material application: Buffer materials such as rubber pads and foam plastics are set between batteries and between batteries and structural components to absorb and buffer vibration energy. During vehicle operation or equipment running, cushioning materials can reduce the impact force on the battery and protect its safety.

Optimization of shock absorption structure: For some application scenarios with high requirements for vibration, dedicated shock absorption structures can be designed, such as shock absorption springs and dampers. By rationally arranging the shock-absorbing structure, the vibration amplitude of the battery pack in a vibrating environment can be reduced, and the structural stability of the battery pack can be improved.

Third, space utilization and maintainability design

Spatial layout optimization

Compact stacking: Under the premise of meeting safety and structural stability requirements, a compact stacking method should be adopted as much as possible to reduce the space occupied by the battery pack. The space utilization rate can be improved by optimizing the arrangement and spacing of batteries. For instance, by using irregular-shaped batteries or customized battery modules, the gap between batteries can be reduced, thereby increasing the energy density of the battery pack.

Modular design: The battery pack is designed into multiple modules, each containing a certain number of batteries. The modular design facilitates the installation, disassembly and replacement of the battery pack, and also enhances the scalability of the battery pack. When it is necessary to increase the battery capacity, simply add the corresponding module.

Maintainability design

Easy-to-disassemble structure: The battery pack structure is designed to be easy to disassemble, enabling maintenance personnel to conveniently replace damaged batteries or perform other maintenance operations. For instance, detachable end plates and side plates, as well as easy-to-plug and unplug electrical connectors, are adopted to reduce maintenance time and costs.

Maintenance passage setting: Set up reasonable maintenance passages inside the battery pack to facilitate maintenance personnel to enter the battery pack for inspection and repair. The width of the maintenance passage should be designed based on the scale of the battery pack and the size of the maintenance tools to ensure that maintenance personnel can enter and exit freely.

Fourth, optimized design of electrical performance

Battery balancing design

Active balancing circuit: In multi-layer stacked battery packs, due to the performance differences among batteries, it may lead to overcharging or overdischarging of some batteries. The active balancing circuit can monitor the voltage and power of each battery in real time, and transfer the power from high-voltage batteries to low-voltage batteries through energy transfer, achieving balancing among batteries.

Passive balancing design: Passive balancing design typically employs the method of resistance discharge to consume the power of high-voltage batteries through resistors, thereby achieving the purpose of balancing. Although the passive equilibrium design has a relatively low cost, it consumes a certain amount of energy and has a relatively low efficiency.

Electrical connection optimization

Low-resistance connection: Select low-resistance connection materials and connection methods to reduce the resistance loss inside the battery pack. For instance, copper bars are used as electrical connectors between batteries. Copper bars have low resistance and good electrical conductivity, which can enhance the charging and discharging efficiency of battery packs.

Electromagnetic compatibility design: In the electrical connection of battery packs, electromagnetic compatibility issues should be taken into account to prevent electromagnetic interference between battery packs and other electronic devices. Measures such as shielded cables and filters can be adopted to enhance the electromagnetic compatibility of battery packs.