Battling the Cold: How Freezing Weather Impacts Electric Vehicle Performance

The charging rate of an EV can be affected by low temperatures, thus increasing the overall charging time. Furthermore, the lack of a traditional combustion engine requires additional planning and preparation to ensure the vehicle can operate in optimal conditions during winter.

The scientific bases behind the impact of low temperatures on EV charging times are worth examining in the case of any electric car owner who plans to commute with its prized possession all-year round. By understanding how cold weather affects EV charging times and by implementing appropriate strategies, EV owners can confidently and safely navigate the winter months.

The heart of the EV: The inner workings of current battery technology

The most significant way cold weather affects electric vehicles and their batteries is through its impact on charging times. Cold temperatures can significantly slow the rate at which an EV charges, increasing the overall charging time. The most relevant reason behind this phenomenon is that the battery's basic chemical processes get altered, in other words bashing the system at its utmost core functionality.

To get a little bit into the science behind this, when the battery temperature is low, the electrolyte solution inside the battery becomes altered, in turn slowing down the chemical reactions taking place within the battery cell. It means the unit can't accept as much charge as it would at a higher temperature, thus slowing the charging rate. For example, lithium-ion batteries, commonly used in EVs, are known to be quite sensitive to temperature changes.

In addition, the low temperature can affect the electrolyte's ability to transfer ions between the electrodes, which also lowers the overall performance and efficiency of the battery. Based on these mechanisms, a battery's total capacity decreases with every degree of temperature drop, meaning it can reach a point where the car can't operate at all. Not least, cold temperatures can also cause the battery's internal resistance to increase, which further decreases its performance.

The automotive industry currently uses different battery compounds, such as lithium-ion, nickel-metal hydride, and lead-acid, each with its own advantages and disadvantages regarding cold weather performance.

Lithium-ion batteries, for example, widely used in battery-electric vehicles, may offer a higher energy density and lower internal resistance compared to nickel-metal hydride batteries, but nowhere near could they be considered a suitable answer to efficient cold weather performance. Not only that, but lithium-ion batteries are correspondingly sensitive to high temperatures, which can lead to reduced performance in hot weather, also.

The cold war: How next-generation batteries could win against the winter battle

To address some of these challenges, researchers are developing new technologies that, beyond providing more energy density, decreased charging times, and lower overall costs, will also mitigate the effects of cold temperatures on the battery.

For example, new chemistries such as lithium-sulfur and lithium-air, which have higher energy densities and could provide more stability, thus increased resistance to freezing temperatures, are currently being researched. Additionally, new promising designs of solid-state batteries, which could improve performance and efficiency in extreme temperatures, are also undergoing development.

Lithium-sulfur batteries are a newer type of battery chemistry that has been gaining attention in the EV industry. These batteries have an increased energy density versus current lithium-ion batteries, which means they can store more energy inside the same physical space. Additionally, they are less sensitive to extreme temperatures, making them more suitable for EV use in hot or freezing weather conditions.

Another advantage of lithium-sulfur batteries is that they have a higher lifespan than traditional lithium-ion batteries because the sulfur component of the battery is more stable than other materials used in batteries. It enables lithium-sulfur batteries to maintain their peak performance for an extended period, which can benefit EV owners.

On the other hand, lithium-air batteries, also known as lithium-oxygen batteries, are a newer type of battery chemistry that has been gaining traction in the EV industry.

These batteries operate by combining lithium and oxygen to produce electricity. The lithium serves as the anode, while the oxygen is drawn from the air to serve as the electron donor. When the battery is plugged in, lithium ions move from the anode to the cathode, reacting with oxygen to create lithium peroxide. When the battery is discharging, the lithium peroxide breaks down, releasing oxygen and lithium ions back into the anode.

One of the main advantages of lithium-air batteries is that they have a much higher energy density than traditional lithium-ion batteries. The theoretical energy density of lithium-air batteries is astounding, about 12 kWh/kg (26.5 kWh/lb), which is ten times higher than that of lithium-ion batteries and comes very close to the energy density of gasoline.

One of the main challenges is that these batteries are still in the research stage, and not yet commercially available. The electrodes tend to spontaneously accumulate discharge byproducts such as lithium salts, which can block the porous cathode, thus making them more complex to develop and implement than traditional lithium-ion batteries.

Researchers are trying to find efficient electrode coatings that could mitigate this issue. However, there still is a long way to go until this technology will be proven dependable enough to be fitted into commercially available EVs.

Solid-state batteries are a type of battery chemistry that uses solid electrodes and electrolytes instead of the liquid or gel designs found in traditional lithium-ion batteries.

These batteries offer several potential advantages over traditional lithium-ion batteries, including higher energy density, improved safety, and better performance in cold weather conditions versus the existing technologies.

Their solid-state architecture may be highly beneficial when it comes to extreme temperature driving, as the electrolyte solution in a solid form should be less susceptible to density changes in harsh climates.

Despite these advantages, solid-state batteries are still relatively new, and some challenges still need to be resolved before they can be widely adopted in the EV industry. One of their main disadvantages is that the solid electrolyte design inherits an increased internal resistance that is difficult to overcome in an efficient manner, and for this reason, solid-state batteries are still in the research and development stage, and not yet commercially available.

Beyond the batteries

Cold weather can also affect other components of an electric vehicle (EV), besides the battery. The electric motor, gearbox (some EVs are fitted with a two-speed or higher-geared transmission to protect the drivetrain during hard accelerations), and other mechanical components of the car may be affected by cold temperatures, leading to a decrease in performance. Also, chilly temperatures can cause the motor to work harder, leading to increased wear and tear.

Of course, the tires can also be affected by cold temperatures. Although some EVs use specially developed rubber compounds designed with maximum efficiency in mind, they can become more rigid in the cold, leading to decreased traction and handling.

Using the car's heating system further affects the vehicle's total driving range, especially if it is fitted with a resistive system which is far more inefficient than a heat-pump solution found in newer models.

The vehicle's charging system can also be affected by cold temperatures. Low temperatures can stall charging rates, as the actual charging equipment can work less efficiently.

Impact of the cold weather on the charging infrastructure itself

Furthermore, cold weather can also affect the charging infrastructure, with some charging stations not functioning well in extremely low temperatures.

When it comes to plugging in an electric vehicle, choosing the right type of charger is crucial when talking about charging times. There are three main types of commonly available units: Level 1, Level 2, and DC fast chargers. During winter, all EV charging methods may take longer, but this is particularly true for DC fast charging.

Level 1 chargers are the most basic type and are typically found in residential settings. They use a standard 120-volt household outlet and can take around 20 hours to entirely charge an EV, depending on its battery size. They tend not to be affected by the cold weather and are a good option for overnight charging at home because of their slow rates of charging, which, in a way, provides a "friendly" interaction with the battery chemicals, considering their current behavior in the cold.

Level 2 chargers are more potent than the Level 1 alternative and use a 240-volt outlet. Depending on the vehicle and the charger's capacity, they can charge an EV in 4-8 hours. However, Level 2 chargers are more affected by cold weather than Level 1 chargers, as low temperatures can significantly slow their charging rate.

DC fast chargers pertain to the Level 3 category and are considered the most powerful charging solution. They can juice up an EV in as little as 20-30 minutes, but they are also the most affected by cold weather. Low temperatures can severely reduce their charging rate, with some charging stations not functioning well in extremely low temperatures.

When choosing a charging method during the winter months, it's essential to consider the charging rate and the equipment's susceptibility to cold weather. Level 1 chargers are a good option for overnight charging at home, but Level 2 and DC fast chargers may not be as suitable in sub-freezing temperatures unless the battery was already preconditioned using manufacturer-specific guidelines.

For example, Tesla recommends using the Trip Planner to navigate to a charging location, no matter if the driver already knows the route to that respective location, because, on the way there, the vehicle's software can automatically optimize the battery's behavior, increasing its temperature, which helps efficiently adapt to rapid charging conditions despite the harsh conditions. If the drive to the charging location is less than 30-45 minutes, drivers can precondition the battery beforehand using the available smartphone app or vehicle infotainment software.

Understanding some basic facts about how cold weather affects the batteries in EVs is crucial for getting optimal performance and range from your electric vehicle during the winter months. EV owners should be aware of the different battery chemistries, how they respond to cold temperatures, and the impact of such conditions on the battery's capacity and performance.

Additionally, it's a good idea to take steps to alleviate the effects of cold weather on their vehicles, including preconditioning the battery, carefully planning charging stops, and adequately maintaining the car according to manufacturer policies. Future developments in EV charging technology may also eliminate some of the cold weather challenges of today and significantly improve the all-year-round EV experience.