Charging speed is an increasingly huge selling point for electric cars. But you may find out that the charging speed can't meet your expectations. This phenomenon is common among EV owners. You shouldn't immediately think there's a fault with the charger or grid connection, though, as maximum charging speed is dependent on several factors. Let's explore why your home charger may not be delivering the expected charging rate to your EV.

Reasons Affecting Charging Efficiency

• Conversion Losses

For most households, the electricity you are using is AC. The process of converting AC from the grid to DC to charge the battery incurs energy losses in the form of heat, impacting overall efficiency.

• Charger's Output or Charging Capacity

One of the most common reasons is that the charger's maximum output is lower than the maximum power your car can accept or that your EV isn't charging as fast as you're expecting it to is a limit to its charging capacity. This mismatch is often the cause for charging speeds below expectation.

• Battery Temperature

Battery temperature will also affect how fast an EV charges. They are designed to work best in a narrow range of optimal temperatures. Extreme temperatures can affect charging efficiency, especially the battery's state of charge and health.

Calculating Charging Efficiency

You know your car's claimed maximum capability and you know the power of the charger… but will they achieve your expectation? Typically, Level 2 charging, prevalent in home and public charging stations, boasts an efficiency range of 85% to 95%. This means that out of every 100 kWh drawn from the grid, 85 to 95 kWh are effectively stored in the vehicle's battery. 

And on paper, it's a simple formula: the charger unit's maximum cable current x your car's maximum battery voltage.