What's the Future: AC or DC?

     Is AC or DC the future of electric vehicles? Alternating current (AC)and direct current(DC) were once caused a minus opinion wars. Some believe that installing a large number of AC charging points will be enough, but others believe that high-power DC charging points are the only way to go.

      Firstly, let’s compare the difference between AC charger and DC charger:

For AC charger, as we know, the converter is built into vehicle, and it converts power from AC to DC then feeds into car’s battery. So, it takes longer time, and typically, it takes approximately 4 – 6 hours to fully charge a EV(battery capacity: 75 kWh.) .

     Unlike AC chargers, DC chargers contain a converter within the charging station itself. That is, it can power the car battery directly without the conversion of onboard charger, thus more power can be supplied as the current has already been converted to DC when it reaches the vehicle. DC charging stations can generate up to 350 kW of electricity and charge electric vehicles in 15 to 30 minutes.

     Secondly, let’s analyze it from the perspective of charging scope:

     Charging infrastructure has four core areas:  

21. Highway long distance charging
21. Public parking lots and supermarket
21. Workplace
21. Your own home

     Due to the difference in charging speed, we can see that on highways, public parking lots or large supermarkets, DC fast charging at DC charging piles is the only economically feasible and practical solution in public places. It makes reaching 80% SoC within 10 minutes possible, which can effectively reduce the driver's waiting anxiety.

     Some people also pointed out that AC charging piles are economical, practical and easy to install at workplace and at home, so AC charging piles are the best choice.

However, according to a research in large urban office building projects, DC power is no longer more expensive than AC power when it exceeds a certain scale. One main charger supplies power to many individual interfaces provides a feasible solution.

     For home application, a growing number of DC wall box will soon prove that bi-directional charging is the best choice. German company 1komma5 Grad provides an example of what advanced home systems will look like in the medium term. The whole thing gets interesting when an electric vehicle with bi-directional charging capabilities is combined with a DC wall box, photovoltaic system and fixed buffer storage unit. In any case, both photovoltaic systems and traction batteries operate on DC, thus avoiding conversion losses from DC to AC.

     Therefore, it is only reasonable to assume DC in the case of 100% electric vehicles. This could take a long time, perhaps until 2050. But it's not impossible.