The principle of strength and rigidity

Meeting load requirements: During the operation of lithium battery packs, they are subject to various loads, such as their own weight, vibration and impact forces during equipment operation, and external collision forces, etc. The mechanical protective structure must have sufficient strength and rigidity to withstand these loads without obvious deformation or damage. For instance, in electric vehicles, the battery pack is installed at the bottom of the vehicle and is subject to the jolts and impacts from the road surface as well as the inertial forces during vehicle operation. The protective structure should ensure that the individual battery cells and electrical connections inside the battery pack are not affected under these complex loads through reasonable material selection and structural design. Generally speaking, for lithium battery packs used in automobiles, after the protective structure undergoes vibration tests of a certain amplitude (such as sinusoidal vibration and random vibration tests in accordance with relevant standards), the deformation should be controlled within a very small range, usually not exceeding 5% of the distance between battery cells, to ensure the stability of the relative position of the battery cells.

Optimize the structural form: Adopting a reasonable structural form can enhance the strength and rigidity of the protective structure. Common structural forms include frame type, box type, etc. The frame structure is composed of crisscrossing beams or members, which can effectively disperse the load and is suitable for battery pack protection with high requirements for space utilization and a certain degree of openness. The box-type structure has better sealing and integrity, which can provide all-round protection for the battery pack and is often used in situations with high protection requirements. For instance, in some large-scale energy storage power stations, battery packs typically adopt a box-type protective structure. The box is welded from high-strength steel plates, with reinforcing ribs set inside to enhance overall rigidity and load-bearing capacity.

The principle of lightweighting

Reducing energy consumption: In many application scenarios, such as electric vehicles and unmanned aerial vehicles, the weight of lithium battery packs has a significant impact on the energy consumption and performance of the equipment. A heavier battery pack will increase the overall weight of the device, resulting in higher energy consumption and shorter driving range. Therefore, mechanical protective structures should, on the premise of meeting the requirements of strength and rigidity, minimize their own weight as much as possible. For instance, in the field of electric vehicles, by replacing traditional steel with lightweight materials such as aluminum alloys and carbon fiber reinforced composites, the weight of the battery pack can be significantly reduced while ensuring protective performance. Generally speaking, the use of aluminum alloy materials can reduce the weight of the battery pack's protective structure by 30% to 50%, thereby increasing the driving range of electric vehicles.

Optimizing materials and structures: In addition to choosing lightweight materials, lightweighting can also be achieved by optimizing structural design. For instance, methods such as thin-walled structures, hollow structures or topological optimization design can be adopted to reduce the amount of materials used while ensuring the structural strength. Topological optimization design can automatically generate the optimal structural shape based on load distribution and performance requirements, making the material distribution more reasonable. For instance, in the design of the protective structure for unmanned aerial vehicle battery packs, through topology optimization, the weight of the protective structure can be reduced by 20% to 30%, while meeting the vibration and shock requirements during flight.

Principle of heat dissipation performance

Effective heat dissipation methods: During the operation of lithium battery packs, heat is generated. If the heat cannot be dissipated in time, it will cause the battery temperature to rise, affecting the battery's performance and lifespan, and may even lead to safety accidents. Therefore, the mechanical protection structure should be designed with effective heat dissipation pathways to ensure that the battery pack can operate within an appropriate temperature range. Common heat dissipation methods include natural heat dissipation, air cooling and liquid cooling, etc. Natural heat dissipation is suitable for battery packs with low power and heat generation. It increases the contact area with the air through heat dissipation holes or heat sinks on the protective structure to promote heat dissipation. Air cooling and heat dissipation use fans to force air to flow, removing the heat generated by the battery pack. Liquid cooling heat dissipation has the advantage of high heat dissipation efficiency and is suitable for high-power and high-heat-generating battery packs. By arranging coolant pipes inside or around the battery pack, the heat is carried away by the circulation of the coolant.

Heat dissipation structure optimization: To enhance the heat dissipation effect, the heat dissipation part of the protective structure can be optimized in design. For instance, the shape, size and arrangement of heat sinks can affect the heat dissipation efficiency. Generally speaking, the larger the surface area of the heat sink and the more appropriate the spacing, the better the heat dissipation effect. At the same time, the contact thermal resistance between the heat sink and the individual battery cells should also be as small as possible. This can be reduced by applying thermal grease to the contact surface and other methods. In a liquid cooling heat dissipation system, the layout and flow rate of the coolant pipes also affect the heat dissipation performance. The pipe direction should be reasonably designed to ensure that the coolant can flow evenly through each battery cell and carry away heat.

Principle of Protective performance

Dust-proof and water-proof: Lithium battery packs are typically used in various complex environments. Therefore, the mechanical protection structure should have excellent dust-proof and water-proof performance to safeguard the battery cells and electrical components inside the battery pack from damage caused by dust, moisture, and other factors. The protection level is usually indicated by IP codes. For instance, IP67 indicates that the protection structure can completely prevent dust from entering and remains unaffected after being immersed in a certain water depth (typically 1 meter) for 30 minutes. To achieve a higher dust-proof and water-proof level, the protective structure should adopt a sealed design, such as using rubber sealing rings, sealants, etc. to seal the connection parts. Meanwhile, the material of the shell should have a certain degree of corrosion resistance to prevent rusting or corrosion in a humid environment.

Shock and vibration resistance: During the operation of the equipment, lithium battery packs will be subject to varying degrees of shock and vibration, such as jolts when a car is driving and collisions during equipment transportation. The mechanical protection structure should have sufficient resistance to shock and vibration to protect the individual battery cells and electrical connections inside the battery pack from damage. The impact resistance performance can be enhanced by increasing the thickness of the protective structure and using cushioning materials, etc. For instance, by filling the interior of the battery pack casing with cushioning materials such as foam plastic and rubber, when impacted, these cushioning materials can absorb and disperse the impact energy, reducing the force exerted on each battery cell. Meanwhile, the protective structure should also fix the battery pack to the equipment through a reasonable fixation method to prevent loosening or displacement during vibration.

The principle of maintainability

Easy to disassemble and assemble: During the use of lithium battery packs, operations such as maintenance, inspection, and replacement of battery cells may be required. Therefore, the mechanical protective structure should be designed in a form that is easy to disassemble and assemble, so that maintenance personnel can operate the battery pack quickly and conveniently. For instance, detachable connection methods such as bolt connection and snap connection should be adopted, and non-detachable connection methods like welding should be avoided. Meanwhile, the connection parts should be provided with reasonable operating space to facilitate disassembly and assembly with tools.

The internal layout is reasonable: The layout of the battery cells and electrical components inside the protective structure should be reasonable to facilitate maintenance personnel's inspection and repair. For instance, there should be sufficient gaps between individual battery cells to enable the use of detection equipment to measure parameters such as voltage and temperature for each cell. Electrical components should be centrally arranged to facilitate line connection and fault detection. In addition, observation Windows or inspection doors can be set up on the protective structure to facilitate maintenance personnel to observe and conduct preliminary inspections of the internal conditions of the battery pack without disassembling the entire protective structure.