Reader asks: ‘Why is electric car charging slower in winter?’
With the arrival of cold weather, most electric car users have noticed that the charging speed at fast chargers is noticeably slower compared to summer temperatures. Why is that?
The answer lies in physics and chemistry
The battery is as important to an electric car as the engine is to a gasoline or diesel car. Maintaining its health and maximum lifespan is a priority for both car manufacturers and users.
Battery charging and discharging is a chemical process that is directly affected by temperature and environmental conditions. In winter, the chemical reaction in the battery is slower, which means that the battery cannot accept the charging current as quickly as in warmer temperatures.
In cold weather, the car itself limits the charging speed
The main reason for the decrease in charging speed is not the charger, but the temperature of the battery itself. The electric car’s control system detects the temperature of the battery and the surrounding environment and slows down charging to prevent excessive stress that can damage the battery. During the charging process, the battery temperature rises, which also increases the charging speed.
Therefore, it is recommended to drive for at least 10–15 minutes before charging, so that by the time charging starts, the battery temperature has risen, the charging is ‘healthier’ for the battery, and the speed is higher. To give you an analogy from everyday life, you shouldn’t put a hypothermic person in a hot sauna, but rather warm them gradually.
In addition to battery temperature, the following factors also affect charging speed.
- Charger power: how much power the charger can provide to the vehicle (eg 50 kW, 150 kW, 180 kW, and so on).
- Car capacity: each car and battery system has its own specific charging speed. It is important to keep in mind that even different versions of the same model from the same car manufacturer can differ from each other.
- Battery capacity: in other words, how much energy is in the car battery when charging begins. Charging speed is usually fastest when the battery is empty and slower when there is more energy.
Why does battery temperature affect charging speed?
As we mentioned at the beginning of the article, energy is stored and released in a battery through chemical reactions. As the temperature drops, these reactions become less efficient. For instance:
- in lithium-ion batteries (which are common in electric cars): at low temperatures, the viscosity of the electrolyte increases, making it difficult for lithium ions to move between the anode and cathode. This results in slower charging speeds;
- internal resistance increases in cold temperatures: higher resistance means that more heat is generated during charging, and the system limits the current to prevent overheating or damage to the battery.
How to make the most of fast charging in winter?
- Drive before charging: in cold weather, it is recommended not to charge the battery immediately after a long period of parking, when the car has been standing without use. The car battery heats up when you drive, so it is a good idea to drive the car before using the fast charger in order to warm up the battery for charging.
- Use preheating: many electric cars offer the option of preheating the battery and interior before driving if the car is connected to a charger. This reduces energy consumption while driving and promotes faster charging.
- Plan your charging rationally: in winter, it makes sense to charge after a long drive when the battery is already warm. In summer, on the other hand, it is a good idea to start charging before a long drive to prevent the battery from overheating.
Here you can find more useful tips on how to drive an electric car in cold weather and slippery conditions.
If you would like more information on electric vehicle charging solutions or have any other questions, we are here to help. Please contact us at [email protected], call 777 3030, or leave a consultation request on our website.