What is the Duration to Charge an Electric Vehicle (EV)?
With increasing traction towards eco-friendly transportation, electric vehicles (EVs) are gaining more recognition from potential new car owners. Comprehending EV charging, particularly charging durations, is crucial. This information is useful for daily usage and long-trip planning, and it addresses the primary question of potential buyers: How much time is needed to charge an electric vehicle?
Around the globe, the demand for EVs is on the rise. Recent market studies predict that by 2030, nearly 20% of all vehicles, in the United States as well as the European Union, will be electric-powered, reflecting the increasing acceptance of EVs in these markets. This growth is supported by substantial advancements in battery technology and charging speed. Contemporary EVs now feature batteries with higher voltages and improved energy density, facilitating quicker charging and lessening the duration to charge an electric vehicle.
Knowing the factors that impact the charging duration of an electric vehicle is crucial to owning one. This article delves into these elements, providing insights on what current and prospective electric car owners can expect in terms of EV charging durations.
Elements Affecting the Charging Duration of an EV
The charging duration of an electric vehicle can significantly fluctuate based on several vital elements. Understanding these aspects can assist drivers in effectively managing their electric car charging schedules and expectations. Here's a detailed explanation of these influencing factors:
- Battery Capacity: The size of an EV's battery, generally measured in kilowatt-hours (kWh), primarily determines the charging duration. Bigger batteries, which can store more energy, take longer to charge compared to smaller ones. For instance, an electric vehicle with a 30 kWh battery will charge quicker than a 100 kWh battery, provided all other conditions remain constant.
- Battery Structure (Voltage Systems): Modern EVs feature either 400-volt or 800-volt battery systems. Vehicles with higher-voltage systems, like Tesla’s Cyber truck or the Porsche Taycan, can tolerate quicker charging rates. For instance, a 400-volt EV might max out at around 150 kW, while an 800-volt EV could potentially manage charging rates up to 360 kW or higher. Vehicles with higher voltages can recharge quicker with 800-volt charging, significantly decreasing the total charging duration.
- Initial Battery Charge (SOC): The charging duration also depends on the initial charge state of the battery when plugged in, pretty much where the battery stands (empty 0% vs 100% full). Batteries charge quicker when at a lower charge state (emptier) and slow down as they approach full capacity. As the battery nears full charge, EV charging units reduce power output to maintain battery health and safety. With AC charging stations, the charging speed stays relatively consistent. However, DC fast charging stations typically reach the quickest charging speeds when the battery is between 20% and 60%. As the battery level approaches 80% to 100%, the charging rate drastically slows down for battery health and safety.
- Maximum Charge Acceptance Rate of the Vehicle: Every electric vehicle has a maximum charging rate it can handle, which might be lower than what the charging station can provide. If an electric car’s maximum charge rate is 100 kW, it won’t charge quicker even if it’s connected to a 180 kW charger. This rate is decided by the vehicle’s onboard charging hardware and battery management systems. Generally, all-electric vehicles have two charge acceptance rates: one for AC charging and the other for DC fast charging.
- Power Output of the Charging Station: The maximum output of the charging station, or how much power it can provide, plays a pivotal role. Even if a vehicle can accept high power levels, the duration to charge will depend on whether the charging station can deliver that power. Variations in station output can significantly impact charging durations. Charging stations are available in three different levels, which determine the charging speed – more on this later.
- Environmental Aspects: Extreme temperatures can affect battery performance and charging speed. In cold weather, batteries might require preheating using energy from the charger, which can slow down the charging speed. Similarly, cooling systems might need to operate in extremely hot conditions to maintain the battery at an optimal temperature, affecting overall charging efficiency.
After understanding the factors that impact how long it takes to charge an electric vehicle, it's evident that the selection of charging station plays a crucial role. Each type of charging station, classified into distinct levels, offers varying power outputs and, consequently, different charging speeds. Comprehending these levels is crucial as they assist in planning charging sessions and selecting the right electric car and charging infrastructure to meet lifestyle and travel requirements.
Charging time (hours) = Battery capacity (kWh) – Remaining battery capacity / Charging power (kW) or Charge acceptance rate of vehicle (kW), whichever is lower. See the illustration below.
This formula estimates how long it takes to charge an EV with an AC charger. See the illustration below.
Instructions for Computation:
- Determine Battery Capacity: The total power storage ability of your EV's battery is indicated in kWh. For example, if your battery power capability is 80 kWh, this is the number you will use.
- Assess Current Battery State of Charge: Verify the level of charge remaining in your battery. This detail can be seen on your in-vehicle screen. If your battery is half full and the full capacity is 80 kWh, the existing power level is 40 kWh. Hence, an additional 40 kWh is needed to achieve a full charge.
- Charger Power Output: This refers to the maximum power delivery rate a charging station can provide your EV, and is measured in kW.
- Vehicle Charge Acceptance Rate: This represents the highest power level in kW that the battery of your EV can receive from either an AC or a DC charger. The power absorption rate from a DC charger is generally much more significant than from an AC charger.
- Calculate Charging Time: Subtract the existing battery charge level from the total capacity to find out how much energy is needed. Then, divide this number by the power output of your charger or the vehicle's charge acceptance rate, whichever is lowest.
Example Calculations for EV Charging Times
AC Charging: An EV with an 80 kWh battery, 50% charged, 11 kW charge acceptance rate, using a 7.6 kW Leve| 2 charger:
- Charge needed =80 kWh-40 kWh =40 kWh
- Charging Time = 40 kWh / 7.6 kW=5.26 hours
In this example, we have used the charger's maximum output power, which is lower than the electric vehicle's charge acceptance rate.