You can calculate charger speed and the added range per hour by dividing the rated power of the charger by the energy consumption rate of your Battery Electric Vehicle (BEV).
Here's a breakdown of how to calculate charging speed:
1. Understand the Key Metrics:
- Charger Power (kW): This is the output power of the charger. It's usually labeled on the charger itself. Higher kW means faster charging.
- BEV Energy Consumption (kWh/mile or kWh/100km): This is how much energy your car uses per mile or 100km. You can find this information in your car's manual or display settings.
- Battery Voltage (V): The voltage the charging station can provide (AC) and the voltage the battery pack operates at (DC). Charging stations usually are 240V AC for home use or 480V+ DC for public fast chargers.
- Battery Capacity (kWh): The total amount of energy that your battery can store.
2. The Basic Calculation:
The core formula is:
Charging Speed (miles/hour or km/hour) ≈ Charger Power (kW) / BEV Consumption (kWh/mile or kWh/km)
3. Example:
Let's say you have:
- A 7 kW charger
- A BEV that consumes 0.3 kWh/mile
Then:
Charging Speed ≈ 7 kW / 0.3 kWh/mile ≈ 23.3 miles/hour
This means you'll add about 23.3 miles of range for every hour of charging.
4. Considering Efficiency:
Charging isn't 100% efficient. Some energy is lost as heat. A typical charging efficiency is around 85-95%. To account for this:
- Estimate the charging efficiency (e.g., 90% or 0.9).
- Adjust the charger power:
Effective Charger Power = Charger Power * Efficiency
In our example: Effective Charger Power = 7 kW * 0.9 = 6.3 kW
Recalculate the charging speed: Charging Speed ≈ 6.3 kW / 0.3 kWh/mile ≈ 21 miles/hour
5. Factors Affecting Charging Speed:
- Charger Type (Level 1, Level 2, DC Fast Charging): Different charger types deliver different power levels. DC Fast Chargers are significantly faster.
- Car's Charging Capacity: Your car has a maximum charging rate it can accept. Even if you plug into a very powerful charger, the car will only draw what it can handle.
- Battery State of Charge (SoC): Charging is typically slower when the battery is nearly full (above 80%).
- Temperature: Extreme temperatures can affect charging speed. Some cars actively manage battery temperature during charging.
- Voltage Drop: If your home electrical system cannot provide the voltage requested by the EV, the charging speed can slow.
6. Using Charging Curves:
For a more precise estimate, refer to your car's charging curve (often found in online reviews or forums). A charging curve shows the charging speed at different SoC levels.
In summary, calculating charger speed involves dividing the charger's power output (adjusted for efficiency) by the vehicle's energy consumption rate. Remember to consider other factors that can influence the actual charging speed.
