How Long Does It Take to Charge an Electric Car?

Learning Intention

Students will understand how electrical power affects charging time and calculate how long it takes to charge a battery.

Success Criteria

Students can:

• Describe the relationship between energy (kWh), power (kW), and time (hours)
• Use the formula:

$$\text{Time} = \frac{\text{Energy}}{\text{Power}}$$

• Calculate charging times for an electric vehicle battery.

---

Starter (10 minutes)

Think–Pair–Share

If you plug an electric car into a normal household power point, why does it take much longer to charge than at a fast charger?

Discuss ideas such as:

• power output
• electricity supply
• battery size

Introduce the concept:

• Energy = how much electricity is stored (kWh)
• Power = how fast energy is transferred (kW)

---

Real-World Example (Teacher Explanation)

The Toyota bZ4X has a battery of approximately 71.4 kWh.

This means it stores 71.4 kilowatt-hours of energy when fully charged.

Charging stations provide different power levels:

Charger type	Power
Home power point	2.4 kW
Wall charger	7 kW
Fast charger	150 kW

---

Key Formula

$$\text{Charging Time (hours)} = \frac{\text{Battery Capacity (kWh)}}{\text{Charger Power (kW)}}$$Charging Time (hours)=Charger Power (kW)Battery Capacity (kWh)​

Example:

Charging a 71.4 kWh battery using a 7 kW charger$$Time = \frac{71.4}{7}$$$$Time = 10.2 \text{ hours}$$

So it would take about 10 hours.

---

Student Activity

Part 1 – Charging Time Calculations

The **Toyota bZ4X battery capacity is 71.4 kWh.

Calculate the charging time for the following:

1. Using a 2.4 kW home charger

$$Time = \frac{71.4}{2.4}$$

2. Using a 7 kW wall charger
3. Using a 50 kW public charger
4. Using a 150 kW fast charger

---

Part 2 – Partial Charging

Cars are often charged from 20% to 80%.

1. How much energy is needed to charge from 20% to 80%?
2. If charging at 50 kW, how long will this take?

Hint:$$Energy = Battery \times Percentage$$

---

Part 3 – Real Thinking

Discuss:

1. Why might very fast chargers not always charge at full power?
2. Why do people usually charge at home overnight?
3. Why might the last 20% take longer to charge?

---

Extension Activity

Two versions of the **Toyota bZ4X exist:

• 2WD version: ~150 kW max charging
• AWD version: ~120 kW max charging

If both cars need 40 kWh added, calculate:

1. How long would the FWD take?
2. How long would the AWD take?
3. How much faster is the FWD?

---

Exit Ticket

Students answer:

1. What does kWh measure?
2. What does kW measure?
3. If a 60 kWh battery is charged using a 10 kW charger, how long will it take?