Constant Clamping Force Module Box Design Research

With the rapid development of electric vehicles, people pay attentions to the safety and performance of their power batteries. When lithium battery is in the charging and discharging process, its chemical reaction will lead to its expansion or contraction. But existing products of battery modules have not take this problem into account, which may cause security risks. At the same time, most of the existing modules use mucilage to make up batteries, which is not beneficial to the battery recycling. Designing a kind of constant clamping force module box is necessary, which can compact the batteries by an ideal 2-5kN constant clamping force in the process of expansion. Meanwhile, assemble methods are conducive to the battery recycling. And the strength of the new designed module structure meets the criteria of the national standard under the mechanical shock and random vibration. This study is very meaningful to the safety and performance of the module, as well as resource recycling.First of all, In order to solve the problem of a existing type module box that can't adapt to the expansion of the batteries, by analyzing the performance characteristics of the compaction mechanism, and studying the common variable-stiffness springs and mechanisms, a constant clamping force mechanism inside the module box is designed. The total amount of expansion of the batteries and the performance curve of the constant clamping force mechanism is simulated based on ABAQUS contact analysis. Results show that, the constant clamping force module can provide the battery with the ideal 2-5kN clamping force. The new module structure is simple, and the batteries can be recycled.Secondly, a finite element model of the module structure is set up based on HyperMesh. Using the LS_DYNA restart technology realizes the passing of model plastic strain parameters under the repeated impact loads. Strain and stress nephograms of the model are obtained under three cumulative impact loads. The maximal damage of the model is 0.11 according to the Johnson_Cook failure model, which meets the criteria of the safety test conditions.At last, the work condition of the module structure is analyzed under random vibration loads. The fatigue life nephograms of the model are obtained under the random vibration loads of X, Y, and Z directions. The most dangerous fatigue damage is the element on the joint of angle steels and end covers, of which cumulative life damage of the three directions is 0.56. So the strength meets the criteria of the safety test conditions.In this paper, the expansion and contraction problem of the batteries in the module structure design is solved for the first time. The research methods and ideas of the constant clamping force module box can provide references for the study of the similar power battery system structures.