Source: The article excerpted here is from a post by Green Car Congress analyzing Volkswagen’s engineering decision to allow the new ID.4 electric vehicle to coast when the driver releases the accelerator (much like a gasoline-engined vehicle), a product of the sport utility’s intelligent regenerative braking mode.
WOLFSBURG, Germany – 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?
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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.
The entire post can be viewed by clicking HERE.