What to Consider When Choosing an Electric Motor for Your Car Conversion

After months of research, you’ve finally decided to take the plunge and convert your classic car to electric power. So, what’s next? 

Choosing an electric motor is an exciting part of a car conversion project. After all, the motor is the heart of your car and a crucial component for propulsion. 

However, like the organs of your body, the electric motor doesn’t work in isolation and installing the wrong motor can have wide-ranging repercussions on your conversion, including battery size, performance and maintenance, and of course, the all-important cost factor. 

We’ve taken our collective know-how and rounded up the top considerations for choosing a motor for your classic car conversion. 

Application Requirements

First up, ask yourself how you plan to use your car. City driving? Long-distances? Something in between? 

Charging stations are typically more easily found in city centres, either in public charging areas or in your own charging port at home. As a result, cars primarily used for driving in urban areas require less range for long-distance travel. Additionally, they don’t need to maintain high speeds, unlike when driving on highways.

Conversely, maintaining top speeds on the motorway consumes more power and can quickly drain the battery. Charging ports can be more widely dispersed, with opportunities to stop less frequently. Your car conversion will require an electric motor and battery pack combination that can manage long-distance driving.  

Vehicle Characteristics

The design of your car will have an impact on its speed, power and torque requirements, so weight, size and aerodynamics must be carefully considered when choosing an electric motor. 

Larger, heavier cars will need both more torque and more power.

You may find that space is at a premium under the chassis of your classic car. When choosing your electric motor, you’ll need to make sure there’s enough room for everything, including the motor, a battery pack and anything else you may need, such as a power inverter or a cooling system. 

Battery Capacity/Voltage

Your chosen motor will need a battery to power it, and the battery size ultimately determines your car’s driving range. 

Generally speaking, the higher the voltage, the higher the capacity and the less frequently you’ll need to charge your car. Average EV battery voltages range from 350-400V, but technology improvements can see this go up to 800V. 

It’s better to avoid considering the distance range in isolation, check that your classic car has the physical space and composition to accommodate your preferred motor. Consulting with an electric car conversion professional can save you from making a costly mistake. 

Motor Type

The motor type most suited to your classic car will depend on how you plan to use your car, as well as the factors such as available space, the motor mountings and how it’ll be connected to the wheels.

Electric cars tend to run from AC electric motors: 

  • Synchronous Motors produce high torque at low speeds and are relatively light and compact, making them a good choice for urban driving; 
  • Asynchronous Motors use a magnetic field to turn the rotor, eliminating the need for DC power to get things started. However, they do not have high starting torque and tend to be heavier than synchronous motors. 

Asynchronous motors remain a popular choice for electric vehicles as they tend to be more cost-effective and have lower maintenance needs. 


The efficiency ratio tells us how much of the total energy consumed by the motor is converted into useful energy to move your car, informing us about the car’s range and electricity consumption. 

The type of motor will impact the efficiency of your electric car. Asynchronous motors tend to have a lower energy efficiency ratio of 75-80%, while synchronous motors can achieve 90% efficiency. 

Operating Environment 

Where you plan to use your car, or the operating environment, is as important as how you plan to use it. 

Cars that frequently find themselves driven up steep slopes will need more power than cars driven around on flatter terrain. Unlike the Internal Combustion Engines (ICE) of conventional cars, electric motors cannot sustain peak power continually, but equally, you won’t need an overpowered motor just to deal with the occasional hill climb. 

Maximal Torque

When converting a classic car, it’s all-too-tempting to simply install a motor with equivalent power to the original. However, maximum torque can be a more important factor than the power rating. 

Torque measures the twisting or turning force of the motor. The higher the torque, the better the acceleration. Electric motors develop torque at low or standing revs, which is in stark contrast to combustion engines. As a result, conventional cars compensate with more power to achieve the acceleration rates you’ll need to zip away when the lights turn green. 

Electric motors don’t suffer the same limitation, so you’re often better off choosing a motor with the same maximal torque, rather than matching the power of your car’s original engine. 

Maintenance Requirements

Electric cars tend to have lower maintenance requirements than petrol or diesel cars, but even within the world of electric cars, there can be some variation. Certain electric motors, such as synchronous motors, have more moving parts or need additional components to function. Consequently, these motors may need more maintenance, which can add to your operating costs. 


As with anything in life, there’s a trade-off between cost and performance. It’s always best to carefully weigh up your needs and work out your budget, and then buy the highest quality motor you can afford. 

Choosing the best electric motor is a critical step in your classic car conversion. At Electric Car Converts, our specialists will help you with your electric car conversion journey, assisting you to account for your individual needs, including torque, available space and performance.