There are a number of reasons why traditional petrol and diesel vehicles get better fuel consumption in open driving conditions.
Internal combustion engines are designed so that they perform better at relatively high speeds – according to the Energy Saving Trust, the most efficient speed in terms of fuel economy is between 55mph and 65mph.
City driving also tends to involve far more acceleration and braking than driving on the open road.
This adds to the fuel consumption as a petrol car uses more energy to accelerate than maintaining a steady speed and also loses energy in the form of heat when braking.
It might be expected that a battery electric vehicle (BEV) would perform similarly, but the opposite is true.
According to researchers at the University of Windsor in Canada, the country’s 2022 fuel consumption guide found that electric vehicles that were tested required lower power to drive 100km in cities compared to highways.
A study by the American Automobile Association also found that BEVs achieved a longer range at lower speeds in city driving conditions.
Conducting a series of experiments at the university’s battery management systems research lab, the Windsor team charged and depleted batteries similar to those used in a BEV.
Electric car batteries use more power at higher speeds
The researchers first discharged it at a certain power before fully recharging the battery and discharging it at half the original power.
This was repeated five more times, with the power being halved again each time, before the total energy discharged during each experiment was analysed.
The researchers found that the discharge energy capacity was higher the lower the discharge current.
They concluded that electric vehicles need more power or electric current at higher speeds – such as when driving on a highway compared to in the city.
The batteries also become less efficient at high currents due to energy loss, meaning that they perform less efficiently at higher speeds.
Another factor is that BEVs don’t lose as much energy to braking as some of the kinetic energy is converted back to electricity using regenerative braking systems.
The researchers suggested that power consumption guides for electric vehicles should include the information that drivers can expect to achieve shorter ranges and higher costs per mile at higher speeds.
Today’s news was brought to you by TD SYNNEX – the UK’s number one solutions distributor.
