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Battery System Security

Mar 01, 2018

Regarding the safety of the battery system, we should start with the mechanism of the core material and the design of the electric core. And at the system level to prevent thermal diffusion, this is the whole process of control. In all aspects of safety (chemical, mechanical, electrical and functional), chemical safety requires no ignition, no explosion, and flame retardancy, including the release of toxic gases, including the failure to control heat, which is in chemical safety. Mechanical safety, including vibration and IP level, explosion-proof, anti-collision, prevent compression should be considered. The third is electrical safety, is to put electric shock, leakage, insulation failure and high pressure touch, these are the things that belong to electrical safety. There is also functional security, functional security here is a concept extension, in layman's terms, is when the function failure can not produce security incidents.

Battery safety is the bottom of the car is the core components, to obey the safety of the car, to obey the safety of people. Reliability is designed and manufactured, mainly speaking of the system design layered classification to analyze its failure mode and impact, according to each level to decompose the reliability index, this is a FMEA concept, do Dfmea, Pfmea is in order to identify risks in the design development phase, will bring reliability problems, Even bring security problems, the impact analysis derived from the severity, frequency, detection of various aspects, FMEA analysis is necessary to do, this is the automobile product development.

1. Battery system life. The evaluation of the life of the batteries will be assessed by placing them in the large environment of the battery pack and even the whole vehicle system. The core evaluation has a model, with the storage life and cycle life to assess the user's service life, storage life and cycle life impact mechanism and factors are different. Storage life is mainly the effect of chemical factors, cycle life is the chemical and mechanical effects. In microscopic view, charge and discharge cycle, the electrode plate will expand contraction, SEI interface will appear micro-cracks, repair cracks will consume lithium ions, affecting life.

Why is the power battery cycle relatively good? Because of the power of the pole sheet coating compaction density is relatively low, small expansion, mechanical stress is small. On the contrary, the higher the compaction density, the larger the swelling, the greater the mechanical stress, the greater the impact on the cycle life. So the power-type cycle life will be better than the high-energy batteries. The model assesses the significance of battery life: a year, for example, can evaluate whether the battery can store 8 years 10 years, 500 times within the cycle test data, can predict the whole life cycle can reach 5,000 times, 3,000 cycles.

Finally, the current market is very hot things: fast charge. The fast charging tank system must satisfy at least four conditions: the core performance, overcurrent, thermal management and high voltage connection safety protection must be satisfied.