Audi e-tron Sportback - Recuperation

The battery system of the Audi e-tron Sportback 55 quattro stores 95 kWh of gross energy (86.5 kWh net) and operates at a rated voltage of 396 volts. It is fitted as a wide flat block beneath the passenger cell, to which it is bolted at 35 points. The battery system is exceptionally rigid and crash-proof-thanks to a solid protective frame and an aluminum laminate that holds the 36 cell modules. These are arranged on two levels, as a long lower "floor" with 31 modules and a short upper floor with five modules. Each module integrates twelve 'pouch cells.' The cooling system is located beneath the cell chamber.

During deceleration actions of up to 0.3 g-which applies to over 90 percent of such actions in everyday driving-the high-voltage battery is charged by the electric motors, primarily by the rear electric motor, which act as generators in these situations. The recuperation system provides for variable regulation of energy recuperation between both electric modules-both in coasting mode when the driver releases the right-hand pedal as well as during braking. The degree of coasting recuperation can be set to three stages by means of paddles on the steering wheel and is even more strongly differentiated than on the e-tron.

When braking from 100 km/h (62.1 mph), the Audi e-tron Sportback can recuperate a maximum of 300 Nm (221.3 lb-ft) and 220 kW. As with its sister model, this amounts to more than 70 percent of its output and more than any other production model. Overall, the SUV-coupé attains up to 30 percent of its range through recuperation.

The wheel brakes, whose innovative electrohydraulic activation concept allows them to respond with exceptional speed, come into play only at deceleration forces greater than 0.3 g. Depending on the driving situation, the control system decides individually for each axle whether the SUV coupé recuperates using just the electric motors, just the wheel brakes, or a combination of both. The transition between electric and hydraulic braking is smooth and homogeneous so the driver does not even notice it. Brake forces remain constant.

On the wheel brakes of the Audi e-tron Sportback, the developers have substantially reduced what is referred to as residual brake torque-the losses that occur during brief application of the brake pads against the disk. This benefits both efficiency and range. The same applies to three additional measures: During normal vehicle operation, the front electric motor is almost completely decoupled from the drive. An increase in the usable range of the high-voltage battery combined with a reduction in several of the volume flows in the coolant circuit means that the pump has to provide less power.

The highly flexible thermal management, which comprises four separate circuits, regulates the temperature of the high-voltage components with maximum efficiency. This enables rapid DC charging, a long battery life cycle, and reproducible performance even under heavy loads. The standard heat pump, which harnesses waste heat from the high-voltage battery, can use up to 3 kW of actual power losses for heating and air conditioning the interior-which is exceptionally efficient. Depending on the outside temperature, that can boost the Audi e-tron Sportback's range by up to ten percent in customer operation.