Types of Charging
AC Charger (Slow Charging): a charger that outputs Alternating Current (AC) power. Used in residential chargers or smaller public stations where drivers are likely to park for a long duration. Likely to take minimally 8 hours or more.
DC Charger (Fast Charging): a charger that outputs Direct Current which flows directly into the battery. This is more efficient than AC charging; often found on highways or commercial sites where speed is a priority. Generally, 50 kW upwards, taking about 30-75 minutes depending on the type of vehicle and state of charge.
Why Does AC Charging Take So Long?
Whenever you feed AC Power into your EV, the convertor gets to work and changes it into the DC power your batteries need. The acceptance rate of this convertor, which varies by manufacturer, impacts the charging speed and time needed to charge an EV. This process requires an additional task to complete, so the AC-fuelled charging speed is relatively slow. All Level 2 charging stations rated between 7 kW and 22 kW use AC power from the power station, so they depend on the rectifier to convert it into DC.
The DC Fast Charging Process
DC power, on the other hand, bypasses the converter altogether so the charge can go directly into the battery. This speeds up the charging process, which is why it’s called fast or rapid charging. Compared to charging with AC power, using DC power for charging is very fast. DC charging offers advantages in situations where quick battery replenishment is either required or preferred. The only limiting factor here is the connector type used to charge the vehicle.
DC chargers come in a range of sizes. Those with lower kilowatt (kW) offerings may be able to charge up to around 50 kW while the fastest chargers go up to 180 or 360 kW. Not many consumer cars right now can accept that much power, so it’s good to know about your own vehicle.
So, Should I Always Charge With A Fast DC Charger?
Well, there are a few reasons why that might not be the best option.
First, it depends on the connector type. Every EV has a max acceptance rate for power. In simple terms, there is a max amount of AC power that the EV will be able to convert to DC. Additionally, there is a max DC power the EV can accept at once. Fast DC chargers use two types of connectors: CCS or CHAdeMO connectors.
Second, fast charging is good only occasionally. The fast-charging rate heats up the battery, which can be bad for batteries. Consequently, regular rapid charging may degrade your EV batteries in the long term.
Third, fast DC charging is more expensive. As it requires high voltage and amperage, the cost of electricity is higher. Also, since this is the fastest way of charging at any public station, you will be charged a higher rate for this kind of charging.
So we hope you now know what DC fast charging is and how it works. You should also now know why the speed of AC home chargers is slower. Next time you want to top up your EV batteries, you will be able to make an informed choice based on your situation. Choose wisely, and save yourself time and money!