Electric motors can provide high power to weight ratios, and batteries can be designed to supply the large currents to support these motors.
Although some electric vehicles have very small motors, 15 kW (20 hp) or less and therefore have modest acceleration, many electric cars have large motors and brisk acceleration. In addition, the relatively constant torque of an electric motor, even at very low speeds tends to increase the acceleration performance of an electric vehicle relative to that of the same rated motor power internal combustion engine. Another early solution was American Motors’ experimental Amitron piggyback system of batteries with one type designed for sustained speeds while a different set boosted acceleration when needed.
Electric vehicles can also use a direct motor-to-wheel configuration which increases the amount of available power. Having multiple motors connected directly to the wheels allows for each of the wheels to be used for both propulsion and as braking systems, thereby increasing traction. In some cases, the motor can be housed directly in the wheel, such as in the Whispering Wheel design, which lowers the vehicle's center of gravity and reduces the number of moving parts. When not fitted with an axle, differential, or transmission, electric vehicles have less drivetrain rotational inertia. However, housing the motor within the wheel can increase the unsprung weight of the wheel, which can have an adverse effect on the handling of the vehicle.
A gearless or single gear design in some EVs eliminates the need for gear shifting, giving such vehicles both smoother acceleration and smoother braking. Because the torque of an electric motor is a function of current, not rotational speed, electric vehicles have a high torque over a larger range of speeds during acceleration, as compared to an internal combustion engine. As there is no delay in developing torque in an EV, EV drivers report generally high satisfaction with acceleration.
The disadvantage of providing high acceleration by high torque from the motor is lowered efficiency due to higher losses in the form of Joule heating in the motor windings caused by the high electric current. This energy loss increases fourfold as the input current is doubled, so the practical limit for sustained torque from an electric motor depends on how well it can be cooled during operation. There is always a compromise between torque and energy efficiency. This limits the top speed of electric vehicles operating on a single gear due to the need to limit the required torque and maintain efficiency at low vehicle speeds.
For example, the Venturi Fetish delivers supercar acceleration despite a relatively modest 220 kW (295 hp), and top speed of around 160 km/h (100 mph). Some DC motor-equipped drag racer EVs, have simple two-speed manual transmissions to improve top speed. The Tesla Roadster 2.5 Sport can accelerate from 0 to 60 mph (97 km/h) in 3.7 seconds with a motor rated at 215 kW (288 hp).