This pertains to several safety and performance considerations:

1. Safety: An extension cord can increase the risk of overheating, fire hazards, and electric shock. Since charging an electric car requires high power, the electric current must be efficiently transferred. An extension cord can lead to voltage loss, heat buildup, and overloading of the cord, especially if it is of insufficient quality or not suitable for the expected power.
   
   

2. Cable thickness: When charging an electric car, it is important to have the appropriate cable thickness to allow sufficient power transfer without overheating. Extension cords are usually designed for lighter appliances and often have a smaller cable diameter, which can lead to increased resistance and heat development when charging a car.
   
   

3. Certification and standards: Charging cables specifically designed for electric vehicles meet strict safety standards and certifications to ensure safe and reliable charging. Extension cords may not be suitable for charging electric cars and may not meet the required standards.
   
   

4. Reduced performance: Using an extension cord can reduce charging efficiency and slow down the charging speed. The extra length and resistance of the cord can lead to energy loss and a longer charging time.

To ensure safety and achieve optimal performance, it is advisable to use a charging cable of sufficient length that is suitable for the expected power of your electric car. If you do not have a suitable socket nearby, you might consider installing an additional charging point at a convenient location.

It is always advisable to consult the instructions and guidelines of the manufacturer of your electric vehicle and the charging equipment, and to seek advice from a certified electrician or supplier if you are unsure about the correct way to charge your car.