How new energy vehicles survive the winter is one of the most concerned issues for car owners, especially in the northern regions with lower temperatures, where warm air conditioning and cruising range seem to always be inversely proportional. Once there is a problem with battery life, the experience of waiting for a trailer in the cold wind becomes even more difficult.
Therefore, Lixiang Auto used a winter vehicle technology event to demonstrate its strategies for overcoming the "shrinkage" of winter cruising range.
However, before providing the answer, Lixiang first addressed the basic question of "why the cruising range in winter is reduced."
Tang Huayin, head of Lixiang Auto's vehicle electric products, explained that the change in the physical properties of materials at low temperatures is the primary reason for the reduction in winter cruising range. Specifically, at -7℃, the rolling resistance of tires increases by 50% compared to normal temperatures, wind resistance increases by 10%, the lubricating oil in the drive system becomes viscous, resulting in a 2% reduction in efficiency, and the drag resistance of calipers and bearings also increases by 50%.
To solve the problem of increased energy consumption caused by these factors, Lixiang Auto has focused on improving the thermal management system and batteries to enhance winter cruising range.
The first step is to improve the efficiency of the air conditioner and the thermal management system. The traditional solution is to use electric drive waste heat for heating, but the electric drive waste heat will pass through the battery when transferred to the cabin to heat it. If the battery power is high, unnecessary energy consumption will occur.
Lixiang Auto's solution is to add an option to bypass the battery in the thermal management system's circuit, allowing the electric drive to directly heat the cabin. This not only speeds up the warm-up process but also saves about 12% in energy consumption.
In addition, Lixiang Auto has redesigned the components of the thermal management system. Tang Huayin introduced that the thermal management integrated module of the Lixiang MEGA integrates 16 main functional components such as pumps, valves, and heat exchangers. By reducing the number of components and shortening the pipeline length by 4.7 meters, heat loss from the pipeline is reduced by 8%.
Secondly, after turning on the air conditioner in the car, the warm and humid air inside encounters the cold glass, causing it to fog up. The common solution is to turn on the external circulation of the air conditioner and introduce dry, cool air from outside the car to defog, but adding additional cold air increases the energy consumption of the air conditioner.
To address this issue, Lixiang Auto proposed the "double-layer air conditioning box" solution. The double-layer air conditioning box introduces an appropriate amount of external air to the upper layer of the air conditioning intake structure, distributing it in the upper space to prevent fogging while allowing occupants to breathe fresh air. The warm air of the internal circulation is distributed in the lower part of the cabin, keeping the feet warm with less energy. Combined with various sensors such as temperature, humidity, and carbon dioxide sensors, Lixiang Auto has developed a more intelligent control algorithm, which can increase the proportion of internal circulating air to over 70% while ensuring no fogging and offering significant energy savings. For example, under the standard working condition of -7℃ CLTC, the double-layer air conditioning box reduces energy consumption by 57W, which translates to an increase in cruising range by 3.6km.
The main reason for battery energy exhaustion in winter is the decrease in electrochemical activity of lithium-ion batteries at low temperatures, leading to increased self-discharge resistance, decreased battery discharge efficiency, and higher energy consumption inside the battery. At the same time, the power capacity of the battery also decreases. Not only may it fail to support normal driving under low power, but it also requires additional energy to heat the battery.
The battery currently installed in the Lixiang MEGA is the Kirin 5C battery, developed jointly by Lixiang Auto and CATL. The battery's power is improved by optimizing the internal resistance of the battery cell and enhancing the heat dissipation of the battery pack.
According to Tang Huayin, the internal resistance of the Lixiang MEGA battery can be reduced by 40% at room temperature, and by 30% under low-temperature conditions, increasing power capacity by 30%.
Unlike the MEGA, the new Lixiang L6 is equipped with lithium iron phosphate batteries. The main issue with lithium iron phosphate batteries is inaccurate power estimation. The common solution in the industry is to recommend users regularly charge the battery for calibration, but this doesn't fundamentally solve the problem of inaccurate power estimation.
To address this issue, Lixiang Auto independently developed the ATR adaptive trajectory reconstruction algorithm, which is first applied to the new Lixiang L6. This algorithm enables automatic calibration of power based on the charging and discharging trajectory during the owner's daily use of the car. Even if the user is unsatisfied with charging for a long time or only drives on fuel, the power estimation error can be kept within 3% to 5%, which is more than 50% better than the industry norm.
Furthermore, the low-temperature environment in winter weakens battery discharge capacity, and the range extender starts prematurely when the remaining power is high, resulting in shorter pure electric driving mileage, which has always been a problem for new energy vehicle owners. To address this, Lixiang Auto launched its self-developed APC power control algorithm. Through a high-precision battery voltage prediction model, it enables millisecond-level prediction of the maximum battery capacity under future working conditions, maximizing the release of power within the safety limits.
Tang Huayin stated that with the APC algorithm, the peak power of the Lixiang L6's battery in low-temperature environments has increased by more than 30%, and the discharge power before the range extender is activated has also increased by more than 12%.