One of the greatest efficiency advantages electric vehicles offer compared to combustion-only models involves recovering energy under braking. A recent test from ADAC (the General German Automobile Club) shows that EVs can recover up to 50% of their energy via regenerative braking. However, there are great differences between various models, with this being illustrated by testing a Dacia Spring and a BMW i7.
ADAC’s test started with the specialists recording the Kesselberg and then recreating this famous Bavarian mountain road’s profile—including the route and incline—on the test bench. This meant the tested vehicles’ energy consumption and recovery could be assessed while driving uphill and downhill.
The procedure, which took place at the ADAC technology center in Landsberg, included a Dacia Spring (single-motor, FWD, 33 kW/45 hp and 1,180 kg), and a BMW i7 xDrive60 (dual-motor, AWD, 400 kW/544 hp, 2,380 kg).
The Dacia Spring can recover up to a third of its energy under braking, while the BMW i7 goes up to half
The results? The Dacia Spring recovered 35% of the energy used while going uphill during the descent, and the BMW 50%. To be more precise, the Spring needed 26.4 kWh/100 km on the uphill route while registering -7.1 kWh/100 km on the downhill section, with an overall result of 9.7 kWh/100 km. The i7 required 59.3 kWh/100 km to go uphill and registered -26.3 kWh/100 km for the downhill part, with a total of 16.5 kWh/100 km.
So keep in mind that while the BMW i7 did recover more than the Spring can even take in when plugged into a charging station, the lighter, less powerful Dacia was more efficient overall in the mountain driving scenario.
The differences between the extremes, the Spring and the i7, are normal. That’s because the efficiency of an EV under regenerative braking depends mostly on weight (with more mass in motion, there’s more recuperation required to decelerate), the number and power of electric motors (the more, the better), and the battery, which needs to be able to absorb the recovered energy and have a certain depletion that allows the energy to flow back in.
For the record, hybrid vehicles also have regenerative braking, even though only the larger batteries of plug-in hybrids can make full use of the energy gained via regenerative braking.
EV energy recovery on flat terrain according to the WLTP cycle also tested by ADAC
Since many, if not most, driving scenarios are comprised mostly of flat terrain, ADAC has also performed Green NCAP measurements of how much energy electric vehicles can recover under braking.
The ADAC simulation was done according to the official WLTP driving cycle, assessing 19 different electric cars, so an important part of the market. All the vehicles received the same conditions, being tested at an ambient temperature of 23 degrees Celsius and having a partially depleted battery.
On average, EVs recover 22% of their energy via regenerative braking when driving on flat terrain. Out of the 19 vehicles tested, the Nio ET7 was the leader (31%), with the Hyundai Ioniq 6 coming close (29%). The Dacia Spring came last (9%), while the Cupra Born also scored below average (16%). The regenerative braking flat driving test also included two Teslas, the Model 3 (23%) and the Model S (24%).
The values above are the WLTP mix (specific average). This includes city driving—frequent braking brings the most recovery here (33% average)—country roads (21%) and highways (the maximum speed of 130% and almost no braking brings the energy recuperation average down to 12%).
So while, once again, heavier EVs with more than one motor, will recover the most energy via regenerative braking, lighter, single-motor EVs naturally remain more efficient overall.
Via: ADAC