Charging Systems

Charging is how EVs "refuel." Understanding charging standards, power levels, and charging curves is essential for EV adoption. India is rapidly building charging infrastructure, but compatibility and availability remain key concerns.

Charging Levels

AC Charging (Level 1 & 2)

• Power: 1.4-2.4 kW
• Connector: Standard household plug
• Use case: Emergency/overnight charging
• Time: 20-40 hours for full charge

• Power: 3.3-22 kW
• Connector: Type 2 (Europe/India), Type 1 (US/Japan)
• Use case: Home, workplace, public
• Time: 4-10 hours for full charge

DC Fast Charging (Level 3)

Charging Time Calculator

Why Charging Slows Down

Charging follows a CC-CV (Constant Current - Constant Voltage) profile:

• Battery accepts maximum current
• Power is constant (or ramping up)
• Fastest charging phase
• Typically 0-80% SOC

• Battery voltage reaches maximum
• Current tapers down gradually
• Power decreases significantly
• 80-100% SOC takes as long as 20-80%

Charging Time Formula

$$t = \frac{(SOC_{final} - SOC_{initial}) \times C_{battery}}{P_{charger}}$$

$$t_{total} = t_{CC} + t_{CV}$$

$$t_{CV} \approx \tau \times \ln\left(\frac{I_{CC}}{I_{cutoff}}\right)$$

Example Calculation

• 50 kW DC charger
• 10% to 80% charge

$$t = \frac{0.70 \times 40.5}{50} \times 60 = 34 \text{ minutes}$$

Actual time: ~45 minutes (includes taper and derating)

Indian Charging Standards

Bharat Standards

• Power: 3.3 kW
• Connector: IEC 60309 (industrial plug)
• Voltage: 230V, single phase
• Current: 15A

• Power: 15 kW
• Connector: GB/T based
• Voltage: 72-200V DC
• Current: 200A max

CCS2 Adoption

India has adopted CCS2 as the standard for DC fast charging:

• All new DC chargers must support CCS2
• Most new EVs come with CCS2 port
• Interoperability with European standards

Charging Infrastructure

• Tata Power: 4,000+ chargers
• EESL: 2,000+ chargers
• Ather Grid: 1,500+ (two-wheeler focused)
• ChargeZone, Statiq, Kazam: Growing networks

• Limited DC fast charging outside highways
• Inconsistent pricing across networks
• App fragmentation (each network has own app)

Charging Curves

Factors Affecting Charging Speed

• Cold battery (<15°C): Reduced charging speed
• Optimal (25-35°C): Full speed
• Hot (>40°C): Reduced to prevent damage

• 0-50%: Full speed typically
• 50-80%: May start tapering
• 80-100%: Significant taper

• Degraded batteries accept less current
• BMS limits charging to protect cells

• Shared power with other vehicles
• Grid constraints
• Cable current limits

Peak vs Sustained Power

Marketing claims often use peak charging power:

• Porsche Taycan: "270 kW charging"
• Actual: 270 kW for a few minutes, then tapers

Onboard Charger (OBC)

The OBC limits AC charging speed:

Charging Economics

Cost Comparison (India, 2024)

Charging at Home

• Dedicated 15A/16A circuit
• Earthing/grounding essential
• Smart charger recommended (scheduling, metering)

Battery Preconditioning

For optimal DC fast charging:

• Faster charging (10-20% improvement)
• Less stress on battery
• Better cold weather performance

Vehicle-to-Grid (V2G)

Emerging technology allowing EVs to export power:

• Peak shaving (export during high demand)
• Backup power for home
• Grid stabilization

• Bidirectional charger
• Smart metering
• Grid operator agreement

Key Takeaways

• AC charging (Level 2) is best for home/overnight; DC fast charging for highways
• India uses CCS2 standard for DC fast charging
• Charging tapers significantly after 80% SOC
• Real charging time is longer than simple calculation due to taper
• Home charging is 70-90% cheaper than petrol
• Battery temperature significantly affects charging speed

What's Next

In the next lesson, we'll explore Range & Efficiency — understanding what affects EV range, drive cycles, and how to maximize efficiency.