Volkswagen has provided an overview of the intelligent regenerative braking system on the ID.4 electric SUV. Regenerative braking can significantly boost the range of any electric vehicle.
However, Volkswagen says, what should happen when drivers of electric vehicles take their foot off the right-most pedal is a nuanced design question. Should the electric drive motor act as a generator, converting kinetic energy into electrical energy, or should it run without generating electrical energy, so that the vehicle’s momentum is used for coasting? I.e., regen or coasting?
The answers vary greatly depending on the manufacturer and model. Some electric vehicles recover energy whenever a driver lifts off the right-most pedal after acceleration. In the case of the new ID.4 electric compact SUV, Volkswagen opted for a different strategy: coasting takes priority because conversion of energy inevitably leads to losses. This applies to the D (Drive) position, the default mode, which is automatically activated upon start-up.
The coasting function, whereby drivers take their foot off the accelerator pedal early on, makes for relaxed and predictable driving. Should drivers want to decelerate more, they step on the brake pedal and activate brake energy recuperation.
During the majority of everyday braking maneuvers—up to around 0.25 g of deceleration—the electric drive motor performs the braking alone, while the electric brake servo only activates the friction brakes in situations that demand more stopping power.
The transition from generator-based to hydraulic braking goes almost unnoticed, due to highly accurate and swift brake and drive system control. These systems also make sure that the rear wheels, where brake energy recuperation takes place, always have a sufficient amount of grip.
Each ID.4 features predictive Eco Assistance as standard. It analyzes data from the navigation system and vehicle sensors to provide drivers with effective support in driving efficiently and in a relaxed way. Once the ID.4 approaches a low-speed area, such as urban environments, junctions and bends, Eco Assistance notifies drivers to take their foot off the accelerator pedal.
From this moment on, the system manages optimum coasting and energy recovery without drivers having to intervene. The car responds similarly when it approaches a vehicle ahead that is travelling at a lower speed.
Drivers can use the gear selector rocker switch to change from the D position to B (Brake) at any time. In this mode, the ID.4’s drive almost always recovers energy during lifting off, but not all the way to a standstill. The limit has been set at 0.13 g—enough for clearly noticeable deceleration that won’t confuse drivers of conventional internal combustion engine vehicles: intuitive operation is one of the vehicles’ greatest strengths.
The ID.4 is Volkswagen’s first all-electric SUV and the brand’s first electric world car. At launch in the US, the vehicle will be offered with an 82kWh (gross) battery and a rear-mounted AC permanent-magnet synchronous motor with 201 horsepower, 228 pound-feet of torque and an EPA-estimated 250 miles of range. A powerful, electric all-wheel-drive variant with 302 hp will follow later in 2021.