LR621 battery.Briefly describe the impact of fast charging on Nissan Leaf’s battery and cruising range

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　　Leaf50kW fast charging process, fast charging will automatically end after 1725 seconds, and then start another charging until the battery is fully charged.

　　Use the Leaf's on-board 3.3kW charger for charging. The statistical graph of the current and temperature of fast-charging vehicles and normal charging vehicles every day is as follows. It can be seen that the changes in current are basically the same, indicating that the driving and other conditions of the vehicles are similar. The temperature changes of the DC fast-charging vehicles are more drastic.

　　Battery pack temperature: A comparative analysis of the temperature of the battery packs of the two groups of vehicles within 250 days is as shown below. Before each vehicle starts, when the DC fast charging (DCFC) vehicle sets off in the morning, the average temperature of the battery pack is higher than that of the ACL2 rechargeable battery pack. The temperature is 2.1°C higher, indicating that fast charging still takes considerable time to dissipate the increase in battery core temperature. However, compared with the high temperature of the external environment, this temperature difference has little effect.

　　When the battery is depleted, the battery pack temperature before each charge is shown in the figure below. It can be seen that the temperature difference between DC fast charging (DCFC) vehicles and ACL2 vehicles is further reduced. During driving, the battery pack temperature of DC fast charging (DCFC) vehicles cooled down by an average of 1.1°C, and the battery pack temperature of ACL2 vehicles cooled down by an average of 0.4°C. Therefore, during driving, the battery pack temperature of DCFC vehicles cooled down by an average of 0.4°C. The battery pack temperature is 1.4°C higher, which is basically negligible.

　　When the battery pack charging is completed, the temperature statistics of the two groups of vehicle battery packs are shown in the figure below. It can be seen that the battery pack temperature has increased on average; the average temperature of the DC fast charging (DCFC) battery pack has increased by 6.5°C, and the ACL2 battery has The average temperature rise of the bag is 2.9°C, and the average temperature difference at the end of charging is 4.9°C. The statistical distribution of the temperatures of the two sets of battery packs during the entire test process is shown below. It can be seen that the temperature of the battery pack will not exceed 46°C 95% of the time (including driving, charging, and stationary) of the vehicle.

　　Battery pack capacity: After every 10,000 miles, the battery pack capacity of the four test vehicles was measured. The comparison chart is as follows. It can be seen that the capacity of the four vehicles is basically the same at the beginning and the first 20,000 miles. Starting from the 30,000th mile, the DC fast charging DCFC vehicle capacity attenuation is significantly greater than that of the ACL2 vehicle, with an average of 0.5kWh. However, this attenuation difference is much smaller than the capacity attenuation caused by the vehicle's own driving mileage (charge and discharge cycle) and calendar time. When driving 30,000 miles, the capacity attenuation reaches an average of 3.2kWh, and at 50,000 miles, the capacity attenuation reaches an average of 3.2kWh. During driving mileage, the average capacity attenuation reaches more than 6kWh.

　　Cruising range: The cruising range and capacity of the 45MPH (72km/h) constant speed test are shown in the table below. After 50,000 miles (80,000 kilometers), the cruising range of the four vehicles showed a large degree of attenuation. DC fast charging The average decline was 30%, with ACL2 vehicle dollars declining 21.5%. Year-on-year, capacity attenuation is also a large proportion.

　　To further compare the capacity tests under different conditions, the laboratory is C/3 test conditions, the track test is a constant speed test until the speed of the vehicle cannot be maintained (to maximize the use of power), and the road test is normal driving, starting from full power , and stops when it is prompted that there are still 5 miles of battery life left (part of the battery is not used).

　　Based on the above, it can be seen that: (1) Fast charging will make the temperature of the battery pack 3-4°C higher on average than that of normal slow charging; (2) Fast charging will accelerate the decay of the battery, and the cruising range will be higher than that of normal slow charging. The vehicle decays quickly; (3) The impact of fast charging on capacity decay and cruising range decay is much smaller than the overall impact of the number of charge and discharge cycles and calendar time, and is not a dominant factor.

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