Experimental Investigation of Downhill Regenerative Braking of Electric Vehicles from CAN Bus Data

Regenerative braking in electrified vehicles is particularly useful to recuperate energy when going downhill. The road load of a 2017 Nissan LEAF AZE-0 30 kWh was obtained and used to determine energy losses when going downhill. Data acquisition was performed through the vehicle CAN buses. The analytical losses caused by the road load were compared to the amount of energy not recuperated by regenerative braking. It was concluded that through the use of road load estimation, it was possible to quantify losses in regenerative braking with less than 10.2% error in cases where no friction braking is used. From the road load equation, it was identified that the regenerative braking efficiency can be improved significantly by reducing vehicle speed. The results were compared to those from a 2019 Hyundai KONA Electric 64 kWh, from which it was shown that a combination of stronger regenerative braking during coasting and a higher peak regenerative braking power across a range of vehicle speeds can improve the round-trip regenerative braking efficiency.