What is the reason for the failure of the power battery of the new energy vehicle

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In general, the reason for the first two failures of the single battery may be the consistency of the single battery when the power battery is grouped, and the SOC, capacity, and internal resistance of the single battery are different; During the application process, the consistency difference caused by the application environment difference (such as temperature, charge and discharge current) increases, which aggravates the inconsistency of the single battery.


Single battery failure There are mainly three types of single battery failures: 01 The faulty battery has normal performance and does not need to be replaced. The corresponding faults include low single battery SOC and high single battery SOC.


02 The reactivation energy of the faulty battery declines seriously and should be replaced in time. The corresponding faults include insufficient capacity of the single battery and too large internal resistance of the single battery.


03 The faulty battery affects the driving safety, and the corresponding faults include the internal short circuit of the single battery; the external short circuit of the single battery; the polarity of the single battery is reversed; under the strong vibration of the lithium ion battery, the tabs, active substances on the pole pieces, terminals, External wires and solder joints may break or fall off, causing internal short-circuit or external short-circuit failure in the single cell.


In general, the reason for the first two failures of the single battery may be the consistency of the single battery when the power battery is grouped, and the SOC, capacity, and internal resistance of the single battery are different; During the application process, the consistency difference caused by the application environment difference (such as temperature, charge and discharge current) increases, which aggravates the inconsistency of the single battery.


Battery management system failures Battery management system failures include CAN communication failures, total voltage measurement failures, cell voltage measurement failures, temperature measurement failures, current measurement failures, relay failures, heater failures, and cooling system failures.


Line or connector failure The diagnosis of line or connector failure is equally important to ensure driving safety and vehicle reliability. For example, due to the vibration of the car, the connecting bolts between the batteries may become loose, the contact resistance between the batteries increases, and the virtual connection between the batteries occurs, resulting in an increase in the internal energy loss of the battery pack, resulting in insufficient power and short driving mileage. In extreme cases, it can also lead to high temperature, generate arcs, melt battery electrodes and connecting pieces, and even cause extreme battery safety accidents such as battery fire.


During the operation of the electric vehicle, there may be a relative jump between the single cells, causing the connecting piece between the two cells to break. The electrical connection between the battery box and the electric vehicle is also a high-incidence point of failure. The electrical connector is prone to virtual connection after a long period of vibration, and failures such as easy ablation and poor contact occur.


The common fault causes and troubleshooting methods of the power battery system are shown in the following table: The common faults of several electric vehicle battery devices are shown in the following table: Motor drive system The faults of the motor drive system mainly include motor faults and motor controller faults.


The failure of the motor can be divided into mechanical failure and electrical failure.


The main mechanical failures are damage to the stator core, rotor core, bearing damage and shaft damage. The reasons for the failure are vibration, insufficient lubrication, excessive rotation speed, excessive static load or overheating. Wear, indentation, etc. Corrosion, electrical corrosion and cracking, etc.; electrical faults are mainly stator winding faults and rotor winding faults. The causes of faults include motor winding grounding, short circuit, open circuit, poor contact and cage rotor bar broken.


The faults of the motor controller mainly include IGBT fault, input power line and ground wire fault, rectifier diode short circuit, DC bus grounding error, DC side capacitor short circuit, thyristor short circuit, temperature over-limit alarm, phase current overcurrent, overvoltage and undervoltage Wait for the failure of the high voltage electrical system.

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