Explaining the Difference Between AC and DC in EV Charging
Electric vehicle (EV) charging can seem complicated at first glance, but one of the fundamental concepts that every EV owner should understand is the difference between AC (alternating current) and DC (direct current) charging. Both types of electricity play critical roles in powering your EV, but they operate differently and offer distinct advantages depending on the situation. This blog will break down the difference between AC and DC charging and explain how they fit into your EV charging routine.
Understanding AC (Alternating Current) Charging
AC charging is the most common type of EV charging, especially for home charging setups. Most electricity supplied by homes and businesses comes in the form of alternating current (AC), where the flow of electricity periodically reverses direction.
How AC Charging Works:
When you plug your electric vehicle into an AC charging station, the electricity flows into your vehicle’s onboard charger. This onboard charger then converts the AC power into DC power, which the battery can store. The conversion process is a key limitation in AC charging because the vehicle’s onboard charger can only handle a limited amount of power at any given time.
Benefits of AC Charging:
- Convenience: AC chargers are typically installed at home, making it convenient for overnight charging.
- Cost: AC charging infrastructure is generally cheaper than DC charging, both for the home and public stations.
- Availability: AC chargers are widespread, with most public charging stations in the UK offering AC charging for EVs.
Drawbacks of AC Charging:
- Speed: Because the onboard charger has to convert AC to DC, the charging process is slower. Home AC charging typically ranges from 3.6 kW to 7.4 kW, with some public AC chargers offering up to 22 kW.
AC charging is ideal for everyday use, especially when you're not in a hurry and can charge your vehicle overnight or during the day.
Understanding DC (Direct Current) Charging
DC charging is usually associated with faster, public charging stations, such as those found along motorways or at service stations. Unlike AC, direct current (DC) flows in a single direction, making it easier for the electricity to be stored in your vehicle’s battery.
How DC Charging Works:
With DC charging, the conversion of AC to DC power occurs at the charging station itself, rather than within the vehicle. This allows DC chargers to deliver power directly to the EV battery, bypassing the limitations of the vehicle’s onboard charger. As a result, DC charging is significantly faster than AC charging.
Benefits of DC Charging:
- Speed: DC chargers can deliver power at rates from 50 kW to 350 kW, allowing an EV to be charged from 20% to 80% in as little as 20-30 minutes.
- Long-Distance Travel: DC fast chargers are strategically placed along motorways and at high-traffic areas, making them ideal for long trips where quick recharging is essential.
Drawbacks of DC Charging:
- Cost: Installing and maintaining DC chargers is more expensive, and charging at a DC station is generally more costly than using AC power at home.
- Battery Longevity: Frequent use of DC fast charging may degrade the battery faster over time, although modern EVs are designed to handle it safely.
DC charging is excellent for quick top-ups when you’re on the road and need to recharge your vehicle quickly. However, it's not typically used for daily charging due to cost and potential battery wear.
AC vs DC: Which Is Right for You?
Most EV owners will use a combination of both AC and DC charging depending on their needs. Here’s a quick comparison to help you decide which to use in different scenarios:FeatureAC ChargingDC ChargingSpeedSlower, typically 3.6 kW - 22 kWFaster, 50 kW - 350 kWCostGenerally cheaperMore expensiveConvenienceIdeal for home and workplace chargingBest for long trips or quick rechargesBattery ImpactMinimal impact on battery healthMay accelerate battery wear with frequent use
Conclusion
Both AC and DC charging serve essential roles in the EV ecosystem. AC charging is perfect for home and overnight use, providing a slow but steady charge at a lower cost. DC charging, on the other hand, offers speed and convenience for long-distance travel or when you need a quick boost. Understanding when to use each type will optimise your EV charging routine and ensure that your vehicle remains ready for any journey.