Introduction:
In plug-in hybrids and fully electric vehicles, we discuss capacity and power. These data are essential when purchasing a vehicle as they help determine, among other things, the range and charging times. For many, the key question for choosing a car is: How many miles does a vehicle travel on a single charge, and how quickly does the battery recharge from empty to full? We often encounter the units kW and kWh, but confusion frequently arises about their exact meaning. In this section, we explore the meanings of capacity and power alongside the units kW and kWh. Additionally, we describe what the consumption of an EV entails and the three ways consumption can be found in instructions or displayed on the dashboard.
Range:
Range refers to the distance a vehicle can travel on one tank of fuel or a full battery charge. It is expressed in kilometers. Many factors can negatively impact the range. Below are a few considerations:
- driving style: rapid acceleration and incorrect engine braking:
– internal combustion engine: the engine does not inject fuel during deceleration;
– electric vehicle: energy is recuperated to the battery during gentle braking. During harsh braking, energy is “lost” as the brake pads press against the rotors; - vehicle weight: more weight results in higher consumption;
- aerodynamics: a bike rack or roof box increases consumption due to air resistance;
- low tire pressure;
- low outside air temperature;
- many engaged electrical consumers (such as seat heating or electric heater);
- engaged air conditioning.
The driver has a significant influence on the range. By considering the above points, vehicle consumption can be reduced, achieving a higher range.
Power [kW]:
Power is the amount of energy that can be delivered in one second. Energy is measured in joules. 1 J/s (joules per second) equals 1 Ws (watt-second). The term watt-second is uncommon, and we refer to the unit as “watt.”
1 kW = 1000 watts = 1000 J/s = 1000 joules in 1 second.
In electric vehicles, power is encountered during the charging or discharging of the vehicle and the power delivered to the wheels:
- charging via an emergency charger (mode 2) at home from a wall socket with a power of 2.3 kW;
- charging via a fast charger along the highway (mode 4) with a power of 43 kW;
- the power delivered by the electric motor (torque multiplied by angular speed) without accounting for losses in the drivetrain:
– BMW iX3: 210 kW;
– Peugeot e-208: 115 kW;
– Volkswagen ID.5: 128 kW.
Capacity [kWh]:
Capacity refers to the amount of energy a battery can store. The higher the battery’s capacity, the greater the range will be.
In electric vehicles, kilowatt-hour [kWh] is often used as a measure for energy and battery capacity.