ECO Assist offers a recuperation process optimised to the particular situation. It takes into account navigation data, traffic sign recognition and information from the vehicle sensors in its efficiency strategy. Anticipatory driving saves power, thereby extending the range.
ECO Assist coaches the driver with messages when the accelerator can be released, for instance because a speed limit is approaching, and with functions such as gliding and specific control of recuperation. For this purpose, navigation data, traffic sign recognition and information from the intelligent safety assistants (radar and stereo camera) are linked and processed.
ECO Assist continuously generates coasting simulations in the background: depending on the state of charge of the battery and the traffic situation, it computes whether the vehicle should ideally be allowed to coast (or "glide") with the lowest possible driving resistance with the driver's foot off the pedals, or whether it should be decelerated so that the battery can be efficiently charged (recuperation).
ECO Assist takes the following traffic situations and information into account in its driving recommendations and efficiency strategy:
- Route profile (bends, junctions, roundabouts, gradients)
- Speed limits
- Distance from vehicles travelling ahead
Within the limits of the system, ECO Assist controls the overrun according to the situation as soon as the driver's foot leaves the accelerator. The driver is also given a visual prompt to do this: by showing a "foot off the accelerator" symbol in the media display (or if available, in the head-up display). At the same time, a diagram gives the driver the reason for the recommendation (e.g. "Junction ahead" or "Gradient ahead").
ECO Assist predictively computes the driving situation when deciding whether to drive with the lowest resistance or whether to recuperate. Examples include dips in the road, brows or speed limits ahead, which the system recognises from the map data.
- Dip: The vehicle recognises that a downhill gradient is followed by a climb, and that a speed limit is shown. The driver receives the prompt "Foot off accelerator" in good time. As soon as the driver acts on this, the vehicle continues with the drive switched off. Recuperation takes place on the downhill stretch, but only enough to ensure that the maximum permitted speed is maintained. Recuperation ends just before the lowest point in the dip, and coasting commences, in order to maintain as much impetus as possible for the uphill stretch.
- Brow: If ECO Assist recognises that "gliding" makes sense on account of the individual driving situation, the topography and the speed limits, the driver is told to "remove foot from accelerator" even before reaching the brow. The vehicle then drives over the brow in "gliding" mode, and subsequently uses the downhill stretch to reach the target speed.
- Speed limit: When the system recognises a speed limit from the navigation data or via Traffic Sign Assist, the driver is once again prompted with "Foot off accelerator pedal". The vehicle is then gently decelerated (while recuperating) to the new speed, followed by coasting. In this way suitable speeds for junctions, roundabouts and bends are also supported.
- Slow-moving traffic: When the radar sensors of the system recognise slow-moving vehicles ahead while coasting, gliding is automatically interrupted if necessary. Deceleration with recuperation takes place to the extent that braking action by the driver is often unnecessary. If the vehicle ahead accelerates, coasting is reactivated automatically so as to cease deceleration and maintain the current speed as much as possible. The driver operates the accelerator if needed.
The EQA offers various ways to recoup energy through recuperation. In general terms the process involves recharging the high-voltage battery by converting the mechanical rotation in overrun mode or during braking into electrical energy.
The driver can select the recuperation function manually using paddles behind the steering wheel. The two paddles behind the steering wheel can be used to influence the recuperation level. The paddle on the left increases the level of recuperation, the paddle on the right reduces it. The driver can see the selected setting in the instrument cluster. The following recuperation stages are available: DAuto (recuperation via ECO Assist to suit the particular situation, see next section), D+ (coasting), D (low recuperation), D- (medium recuperation) and D- -(high recuperation). New with the EQA is that, if the function DAuto is selected, this mode remains the setting when the car is restarted. To stop, the driver must activate the brake as normal, whatever the recuperation stage.