Consumption and driving range

1. Basic quantities

2. Driving cycles

New European Driving Cycle (NEDC)

• This is a recently used driving cycle for determining consumption.

WLTP (Worldwide harmonized Light vehicles Test Procedures)

• This is the current standard driving cycle.
  
• Power/weight ratio Pw (W/Tonne)
• Class 1 - low power vehicles, Pw <= 22
• Class 2 – vehicles, 22 < Pw <= 34
• Class 3 - high-power vehicles, P > 34
  

FTP 75 (USA)

3. Traction battery capacity

• Previously, the battery capacity of purely electric vehicles usually ranged from about 15 to 30 kWh, the normal range of such vehicles was about 80 - 200 km.
• Today, batteries> 30 kWh common, a normal range of hundreds of km.
• Development of vehicles from the beginning as BEV → battery part of the car floor → increase the capacity of the traction battery
• Chevrolet Bolt: 60 kWh
• Tesla: up to 90 kWh (502 km NEDC)
  

4. Indicative values of consumption and driving range

• The average annual consumption of a middle-class passenger car is around 20 kWh / 100 km (eg VW E-Golf).

Influence of temperature

Middle class passenger electric car

The driving range of vehicles with traction batteries can be half that of winter!

5. Consumption measurement on the city ring

Consumption and driving range measurement on a selected city route depending on temperature (season).

5.1. City circuit

5.2. Consumption dependence on temperature

Dependence of drive energy consumption (blue) and comfort consumption (green) on temperature (kWh on urban circuit 37 km, nonlinear x-axis)

Dependence of total energy consumption (blue) and comfort consumption (red) on temperature (kWh on urban circuit 37 km, linear x-axis)

Total consumption as a function of temperature (converted to kWh/100 km, urban circuit 37 km)

Conclusion

5.3. Driving range

Theoretical (recalculated from measurements) driving range (km)

                                                                                             Temperature (°C)

Recalculated vehicle driving range depending on temperature

5.4. Recuperation

• The energy returned back by recuperation is the energy that recharges the battery during braking, when the electric motor is controlled as a generator.
• Recuperation significantly affects the resulting consumption and driving range, especially those rides with frequent braking and accelerations, i.e. mainly in city traffic.
• At low temperatures, the traction battery is more prone to cell disbalancing; the battery management system then limits the amount of charging current and the proportion of recuperation is lower in winter.

                                                                                 Temperature (°C)

6. Main factors influencing consumption

• Temperature
• Driving speed (aerodynamic drag)
• Car weight
• Comfort consumption
  

Electric vehicle consumption depending on speed

7. Comparison with cars with internal combustion engine

Efficiency

• Electric drives are highly efficient compared to drives with internal combustion engines.
• Diesel engine: max. 42%
• Petrol engine: max. 35%
• Electric drive: 75 - 92% in wide operation range
  

Diesel and petrol engine efficiency maps

Electric motor efficiency maps

• Electric drives have a rated torque from zero speed.
• Electric motors can be overloaded for a limited time and thus significantly increase the maximum torque.
• The overload time depends on the warming time (windings, magnets).
• Air-cooled motors of the order of seconds, water-cooled motors of the order of tens of seconds.

Comparison of traction characteristics

8. Driving economics

• The efficiency of an electric car per 100 km is approximately 85% (75% including charging losses).
• The efficiency of a car with an internal combustion engine per 100 km is approximately 20%.

• Thanks to electricity prices (absence of excise duty) and high efficiency of electric drive, the driving economy of electric vehicles is the most favorable of all types of drives.
• However, electricity prices are rising.

Marathon runner                                        Car with petrol engine                      BEV (all season average)

Example

• Consumption - middle class passenger car: winter 26 kWh / 100km, summer 14 kWh / 100km, average 20 kWh / 100km.
• At an electricity price of CZK 4 / kWh, the cost per 1 km of driving is based on:
• 1,04 Kč/km in winter,
• 0,56 Kč/km in summer,
• 0,80 Kč/km in average.

• At an electricity price of CZK 6 / kWh,  the cost per 1 km of driving is based on:
• 1,56 Kč/km in winter,
• 0,84 Kč/km in summer,
• 1,20 Kč/km in average.

• However, the price of electricity may vary at public charging stations.
• Especially fast charging is problematic due to
  
• high losses,
• higher energy prices (9 up to 20 CZK / kWh).