From March 2013, the author began to conduct an omnidirectional evaluation of electric vehicles on sale. Among them are the winter cruising range and charging compatibility evaluation. As we all know, many electric vehicles, including Tesla and Nissan Leaf, will be affected by the weather in winter, which will lead to problems such as shortened cruising range and reduced charging compatibility.
Electric vehicles rely on iron phosphate or ternary lithium-ion batteries as power, and use battery control systems, vehicle control systems and other software to reasonably allocate power to drive the vehicle. Regardless of the material used, the battery will be affected by the low temperature climate, and the reduction of the discharge efficiency will lead to the reduction of the cruising range. It's just that high-quality electric vehicles use "external force" to save the cruising range lost due to low temperatures. The issue of reduced charging compatibility in winter is also an important issue for many car manufacturers to solve.
In fact, the low temperature weather in winter causes the cruising range and charging compatibility problems, which can be classified into one category. The engineers of the vehicle manufacturer must balance the stability, safety, charging speed and reliability of power lithium-ion batteries.
recharge mileage:
On the premise of not adding battery capacity, increasing battery density (increasing battery cell voltage) is the most direct means of increasing the range. However, this method has the risk that the stability of the battery is reduced and abnormal failures are likely to occur. Therefore, engineers either add a new battery heat dissipation (preheating) system or improve the battery cell material (activity and density are at a higher level of stability).
Charging compatibility:
Solving the problem of charging compatibility is the same as the cruising range and stability. It is a breakthrough in contradiction. Through the software, engineers can adjust the battery charging cycle of the vehicle to be shorter, and the charging current and voltage are higher. However, this increase is not unlimited. The increase in voltage and current means a reduction in the charging cycle, and also makes the battery withstand greater impact in a short period of time. Once the safety protection measures are not in place, problems such as spontaneous combustion will occur. Therefore, engineers of vehicle manufacturers have to test many charging facilities on the market and also consider the performance of vehicle battery components under many parameters such as environment, temperature and humidity. After combining many factors, the difference between the charging current of different brands of electric vehicles on sale and the abnormal charging compatibility are caused.
The author takes JAC iEV5 (6S), Geely Emgrand EV, BYD Qin EV (e5) and BAIC New Energy EU260 as examples to compare actual and theoretical winter cruising range and charging compatibility. Because the reference data all come from the relevant evaluation manuscripts written by the author between October 2015 and March 2016 (Beijing autumn and winter)
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