According to our classification of the reasons that can cause the attenuation of low-temperature range of pure electric vehicles in winter, they can generally be divided into objective reasons and subjective reasons.
The objective reason is mainly due to the low temperature, which leads to a decrease in battery activity, and at the same time, high-power electrical appliances in the car also cause a surge in electricity consumption.
In addition, the NEDC standard currently used in China is also one of the factors that leads to significant differences in range between winter and summer.
As for subjective factors, they are more related to the driver’s driving habits and charging habits, after all, pure electric vehicles and traditional fuel vehicles still have essential differences, and cannot be treated in the same way as traditional fuel vehicles.
From a normal perspective, the impact of low temperatures in winter on driving is not only present in pure electric vehicles. Traditional fuel vehicles also experience a direct decrease in engine temperature under low temperature conditions. Before the water temperature reaches normal temperature, the fuel consumption of the vehicle will also increase significantly. However, the increase in fuel consumption of fuel vehicles only exists in the initial few kilometers of vehicle start-up. After the water temperature is normal, all aspects of the vehicle’s performance can return to normal.
In contrast, pure electric vehicles are more affected by low temperatures in winter, and this impact will run through all aspects of pure electric vehicle use, so consumers will have a more obvious feeling.
According to the experimental results of a certain institution, it can be seen that low temperatures in winter have a significant impact on the performance of pure electric vehicle power batteries, especially when the ambient temperature reaches -20 degrees Celsius or even lower, the power battery can only output about 60% of its electricity.
Especially currently, all pure electric vehicles use lithium-ion battery packs as the main material. In low-temperature environments, the internal resistance of lithium-ion batteries increases, the activity decreases, and the charging and discharging power also significantly decreases (such as when the ambient temperature is -25 degrees Celsius, the charging capacity decreases by 80% compared to 5 degrees Celsius, and the discharging capacity decreases by more than 85%). Moreover, low-temperature charging is also prone to negative electrode lithium deposition, which can easily affect battery life and safety.
So the battery BMS control strategy will also limit the working boundary of the battery at low temperatures, resulting in a decrease in the performance of the power battery.
Perhaps it is easier to understand through data display. Currently, the power batteries of pure electric vehicles are mainly made of ternary lithium materials and lithium iron phosphate materials.
Let’s take the ternary lithium material as an example. Assuming the battery level is 50 kilowatt hours and the range is 500 kilometers, when the temperature is 25 degrees Celsius, the vehicle can basically maintain normal state, which means that the 50 kilowatt hour battery can travel 500 kilometers.
When the ambient temperature drops to -20 degrees Celsius, the battery can only output about 60% of its power, which is about 30 kilowatt hours, and the range will correspondingly decline to around 300 kilometers.
As for lithium iron phosphate material, due to its greater emphasis on high temperature resistance, its performance in low-temperature environments is worse than that of ternary lithium material. The battery output capacity at -20 degrees Celsius is only about 55%, which means that in an environment of -20 degrees Celsius, the vehicle’s battery capacity can only output 27.5 kilowatt hours, and the range is only about 275 kilometers.
The above calculations are only based on the theoretical data generated by relevant institutions after testing, and there are far more factors that affect the range of pure electric vehicles. However, with only this one factor, the range of pure electric vehicles has decayed by more than 40%. Adding other factors, the results can be imagined.
Heating the interior of the car also requires battery power consumption. In low temperature environments during winter, there is also a major consumer of electricity, which is heating the interior and battery.
Due to the fact that the power battery carried by pure electric vehicles is the only source of electricity on the vehicle, and pure electric vehicles are not like traditional fuel vehicles that can generate vehicles during driving, the importance of air conditioning is weakened. Air conditioning for pure electric vehicles and heating or insulating the battery also require the energy consumption of the power battery. Therefore, we must not ignore the impact of the electricity consumption on the range of pure electric vehicles.
At present, pure electric vehicles mainly provide heating for the interior through PTC heaters or heat pump air conditioning.
According to relevant information, the energy consumption of PTC heaters is higher than that of heat pump air conditioning. The working power of PTC heaters varies from 3 to 4 kilowatts for different vehicle models, and using them for one hour will consume 3-4 kilowatt hours of electricity.
However, the driving environment for each of us is not the same, and the duration of heating used may also vary. Therefore, the power consumption of PTC heaters cannot be presented in specific values, but theoretically, the energy consumption of air conditioning accounts for about 20%.
Although heat pump air conditioning can reduce the energy consumption of this part to a certain extent, it will increase the cost of pure electric vehicles, so this is also a balance issue.
Taking a pure electric vehicle with a range of 50 kilowatt hours and 500 kilometers as an example, based on the 20% energy consumption of the PTC heater, the theoretical power consumption of a pure electric vehicle at an ambient temperature of -20 degrees Celsius is 40% of the low-temperature power attenuation+20% of the PTC heater. In other words, without considering other factors, a pure electric vehicle has basically consumed 60% of its power and only has about 40% of its range left.
In addition to heating inside the cabin, the power battery also needs to be heated in low-temperature environments to achieve optimal operating temperature.
So many pure electric vehicles are equipped with battery temperature control systems or battery heating systems.
However, what we need to know is that this system, like air conditioning, actually requires energy from the power battery to drive its operation. Therefore, when the battery heating system heats the power battery, it is also consuming the power battery itself.
However, currently no car companies have announced how much electricity is consumed for every 1 degree Celsius increase in battery temperature when using a battery heating system. However, what we can basically determine is that this system also consumes the power battery during use.
The current NEDC standards in China are relatively idealized. Of course, for pure electric vehicle owners, perhaps the most unacceptable thing is the difference between the official nominal range of the vehicle and the actual range, which brings a sense of discrepancy.
And this can be attributed to the relatively ideal testing environment of the NEDC endurance test standard currently used in China, which deviates from the actual driving state.
The NEDC standard is called “New European Driving Cycle”, translated as “New European Driving Cycle” in Chinese. It is a European endurance testing standard that has been implemented in Europe since 1997, and is subsequently cited in China.
This standard consists of four urban cycles and one high-speed cycle.
However, we can also see from the NEDC standard test cycle distribution that this set of standards has a short testing time, less mileage, and a very simple testing method, which can easily lead to significant deviations between the final results and actual results. Therefore, Europe has stopped using NEDC testing since 2018 and instead adopted the new WLTP testing standard.
The full name of WLTP is “World LightVehicle Test Procedure”, which translates to “World Light Vehicle Test Procedure” in Chinese. It is a globally unified set of automotive fuel consumption testing regulations jointly developed by Japan, the United States, the European Union, and others.
The testing time and distance of this standard are much longer than NEDC, and the acceleration and deceleration frequency of the vehicle is also higher, which can better simulate the actual usage environment.
At the same time, this set of standards also takes into account factors such as vehicle rolling resistance, gear, weight, etc., so the final result is much more reliable than NEDC.
In fact, according to relevant plans, after adopting the National VI standard for motor vehicles in China, the range testing standards for pure electric vehicles will also be changed to the WLTC standard derived from the WLTP standard. However, it is unclear why this set of standards has not yet been widely adopted.
From the deviation between the test range and actual mileage, the EPA standard used in the United States is currently the closest evaluation standard to actual use. This set of standards was developed by the National Environmental Protection Agency and consists of FTP75 (urban cycle) and two supplementary cycles (SC03 high-temperature air conditioning full load operation cycle and US06 high-speed and higher acceleration working cycle).
The duration of this set of standards is close to 1900 seconds, and the shifting will be more frequent, including multiple test items where the vehicle comes to a complete stop and then starts, so the EPA standards will be closer to the actual driving environment.
At present, Tesla’s displayed range data in the car is based on EPA standards. Taking the upgraded version of the domestically produced MODEL 3 standard range as an example, the data displayed on the Chinese official website is 468 kilometers under NEDC conditions, but the actual displayed range in the car is only about 380 kilometers.
Of course, in addition to the objective technical reasons we have explained above, there are also some subjective factors that can unconsciously affect the winter endurance performance of pure electric vehicles.
Below we will mainly explain two aspects that affect winter endurance performance, which are actually two driving habits. If you pay more attention to them in daily use, it should be helpful for you to alleviate the decline in winter endurance.
For pure electric vehicles, the biggest difference in usage habits compared to gasoline models is in terms of supplementing energy.
When a gasoline powered car needs to restore its range, it only needs to go to the gas station, take 5-10 minutes to fill up the fuel, and then continue to run hundreds of kilometers.
However, for pure electric vehicles, the current level of charging technology cannot be compared to refueling for gasoline vehicles.
Although the charging rate has increased with the continuous increase of battery capacity, it still takes at least 30-45 minutes to charge the battery to 80% when the battery level is low.
So, many car owners use DC fast charging stations to charge with a mentality of “since they have been waiting for so long, they are full of walking”.
However, for power batteries, frequent use of high current from DC fast charging piles can cause damage to the charging and discharging capabilities of the battery cells to a certain extent.
Especially in high battery conditions, continuing to charge with high current (even when entering the trickle mode with relatively soft charging current, it is still relatively high compared to the current of slow charging piles), coupled with the fact that the charging and discharging capacity of batteries in winter is already affected by temperature, even if the charging current is constrained at a lower level in the charging strategy, it is relatively easy to cause irreversible damage to the battery.
Once damage is caused, it will lead to a decline in endurance, which is irreversible.
So what kind of charging method can minimize the discount on the battery’s carrying capacity as much as possible
If you are limited by the surrounding hardware conditions and can only use DC fast charging piles for recharging in the vast majority of cases, you should pay attention to three points: first, try to recharge the power battery after a period of operation and the battery activity has recovered; Secondly, do not charge the battery too fully. It is advisable to stop charging as long as it reaches the trickle charging mode (the arrival of trickle mode may vary depending on the vehicle model and battery temperature, usually entering trickle charging mode when the battery reaches 80% or 90%). This way, you can also save some time and cost of charging, because in trickle mode, the replenishment of electricity will be slower; Thirdly, regularly go to the 4S store for battery maintenance. The general maintenance method is to leave the car at the 4S store for 1-2 days to perform balanced charging of the battery, in order to help restore the good charging and discharging ability of batteries with partial capacity failure. If you don’t want to leave the car at the 4S store, you can also use slow charging, but be sure to charge the battery to full charge and jump the gun state for better results. In addition, if you have the conditions for slow charging, whether you have slow charging piles near your home or in the parking lot near your company, try to use slow charging piles for recharging. This way, regardless of the season, it is less likely to cause damage to the power battery during the charging process, and it is also less likely to affect the vehicle’s endurance. Another thing to note is not to recharge the battery when it is too low. In this case, the power battery is more likely to be in an over discharge state (over discharge), and it is also more likely to cause irreversible damage to the battery. It is best to recharge between 20% -30% of the remaining power. Perhaps at this point, do you think that the range of electricity I can use is only 50% -70%?
To be honest, at first I was just as surprised as you were, but this driving habit can keep the battery in a relatively good performance state, which helps the vehicle reduce the degree of degradation of its endurance in harsh environments.
Driving habits: Try to treat your accelerator pedal as gently as possible. Additionally, driving habits can affect the vehicle’s endurance. In fact, the truth is that if a gasoline vehicle is frequently driven aggressively, it will consume high fuel and require frequent refueling at gas stations. If a pure electric vehicle is driven in a more aggressive manner, its power consumption will inevitably be higher. As the value of power consumption increases, the distance it can travel under the same level of power will definitely decrease.
Moreover, if conditions permit, try to maintain a constant speed while driving at a speed between 60-80 kilometers per hour, which will put the vehicle in a relatively economical energy consumption range.
As mentioned earlier, battery temperature can affect the charging and discharging performance of the battery, and in winter, it is necessary to heat the battery through a temperature control system to restore its performance.
However, it also takes time to increase the temperature of the battery, so in winter, when the vehicle is just started, it is best not to accelerate quickly, because when the battery performance is poor, high current discharge can also easily damage the battery cells, affecting the capacity of the power battery.
We can also understand it as a “hot car” operation, but there is no need to wait in place. As long as you drive relatively gently for about 5 kilometers, you can basically reach the normal performance state of the power battery.
Of course, in addition to making your feet softer, it is also important to pay attention to traffic safety and efficiency on public roads.
Because in daily driving, there are indeed some drivers who, due to severe mileage anxiety, drive at a lower speed on urban expressways. In fact, if the speed is too low, it can actually increase the energy consumption of the vehicle, and may also cause slow driving in the rear, which is not worth the loss.
Another way is to make good use of the energy recovery system. During driving, as long as there is a difference between the wheel speed and the drive motor speed (the wheel speed is higher than the motor speed), the drive motor will be converted into a generator and the generated electricity will be stored in the power battery; At the same time, the system also generates a certain drag force, causing the vehicle to slow down.
As long as the safety distance is well controlled and the kinetic energy recovery system is used for braking, a portion of the electrical energy can be recovered, reducing the vehicle’s energy consumption, improving its endurance, and reducing the consumption of brake discs to a certain extent, it is a win-win situation.
Compared to gasoline powered vehicles, pure electric vehicles still belong to two different species at the current stage and do require different ways of using them.
Of course, regarding the current data and information, there will definitely be a gap between the range of pure electric vehicles in winter and the official nominal range value. If this gap cannot be clearly communicated to users before purchasing a car, it will definitely create a huge psychological gap for users when using it.
Even with the best charging habits and driving methods, there will be a problem of reduced battery life.
However, we can further reduce the degree of attenuation through various means to ensure our winter driving experience.
