Why is DC charging faster than AC?

In recent years, there has been a growing interest in electric vehicles (EVs) as a more sustainable mode of transportation. One key factor that determines the adoption rate of EVs is the speed of charging. Direct Current (DC) charging, compared to Alternating Current (AC) charging, offers significant advantages in terms of charging time. Let's dive into the technical details to understand why DC charging is faster than AC.

The Fundamental Difference

To comprehend the difference between DC and AC charging, we first need to grasp the fundamental characteristics of these two types of electrical current. Alternating Current (AC) constantly changes its direction, following a sine wave pattern, while Direct Current (DC) flows steadily in only one direction. This basic distinction leads to various implications in terms of power transmission and device compatibility.

Efficiency in Power Conversion

One of the main reasons why DC charging is faster lies in its higher efficiency in power conversion. When electricity is transmitted through power grids or charging stations, it often needs to go through a process of conversion - transforming from high voltage/low current to low voltage/high current - before reaching the battery of an EV. With AC charging, this conversion happens twice, once at the grid level and once at the vehicle's onboard charger. On the other hand, with DC charging, the power can be directly delivered to the vehicle's battery without the need for an onboard converter. This eliminates the loss of energy during the conversion process, resulting in faster charging times.

Overcoming Limitations

AC charging, commonly available in households, possesses certain limitations when it comes to high-power applications like fast-charging EVs. The maximum current residential AC outlets can deliver is typically 16 to 32 Amps. In contrast, DC fast-charging stations can provide currents up to 350 kW, enabling significantly faster charging. While upgrading the electrical infrastructure of households for AC charging may be costly and time-consuming, deploying DC fast-charging stations along highways and public spaces can quickly expand the accessibility and convenience of EV charging.

In conclusion, Direct Current (DC) charging surpasses Alternating Current (AC) charging in terms of speed due to its higher efficiency in power conversion and ability to deliver higher currents. As the demand for electric vehicles continues to rise, further advancements in DC charging technology are expected to make EVs an even more viable option for sustainable transportation.