Real-world performance data harvested from field testing of battery-electric and hybrid vehicles—including details of stop/start and regenerative braking use—highlighted the recent "Electronics Systems for Vehicles" conference, held in mid-October by VDI (The Association of German Engineers) in Baden-Baden. An audience of 1350 attended the event, which is held bi-annually.
John Dennis, representing the hybrid competence center of MAN Truck and Bus, confirmed the benefit of stop/start systems in commercial vehicles. His report was based on results from a fleet of seven diesel-powered series-type hybrid buses and trucks used across Europe. “We found that during 84% of all potential engine-off situations the diesel engine was indeed switched off," Dennis noted.
Probably even more outstanding is the consistent use of regenerative braking in the MAN vehicles. “In only 10% of all braking events, the service brakes were applied. In other words, during 90% of all braking situations, the negative torque of vehicle deceleration was exploited to generate electricity,” he said.
According to Dennis, the overall fuel efficiency benefit recorded among the MAN vehicles ranged between 22% and 27%, compared to an equivalent diesel-powered truck or bus.
Dr. Roland Krüger of FORD-Werke, Germany, reported on feedback from a prototype test fleet of 25 battery-electric vehicles (BEV) in commercial used in Cologne. The fleet has covered 70,000 km (44,000 mi) as of October 2011, with over 1800 charge events. The average daily range of the vehicles is 25 to 70 km (15.5 to 44 mi). However, the average distance between two charge events was found to be just 30 km (18.6 mi).
“The positive feedback unanimously mentions the quiet ride and the vehicle performance. In particular the torque characteristics turned initial skeptics into convinced drivers,” Krüger said. The bottom line is that “BEVs are well suited for goods delivery and service drives. The range anxiety gets lower with increasing BEV usage experience,” he explained.
The effect of regen braking
Volkswagen gave some insight into the average energy consumption of its Golf blue-e-motion BEV test fleet, equipped with a 26.5 kW·h lithium-ion battery and 84.5-kW (113-hp) electric motor.
“We observed an average energy consumption of around 16 kW·h per 100 kilometers," said Thomas Lieber, head of VW's electric traction engineering group. "On average 6.6 kW·h were generated by recuperation. E-drivers are proud to save energy. An e-driver does not brake. Instead he or she will recuperate,” he said.
Still, the results are not all welcome. “We observed 2.9 kW·h per 100 kilometers energy consumption caused by comfort functions. This is way too high," Lieber asserted. He added that another urgent issue that needs to be addressed is the reliability of the remaining range information to the driver. "This must be precise,” he said.
Toward the end of the year, VW will start a fleet test with the 20 Golf blue-e-motion cars in the U.S. To reduce the cost of e-mobility, VW is heavily relying on a modular concept that is expected to reduce the number of variants and increase quality while reducing testing effort.
VW expects e-mobility to have a great cost reduction potential. Ralf Milke, head of VW’s E/E development, chassis electronics, and on-board network, thinks it possible that "the level of cost is halved by each doubling of production numbers and by ongoing technological advance.” However, he adds that “the big construction site of e-mobility is the business case.”
Fuel cell across Europe
Daimler presented findings from 400 BEV and HEV prototype vehicles that covered 10 million km (6.2 million mi) in total. Jürgen Schenk, Director and Chief-Engineer Electric Vehicles for Mercedes-Benz Cars, underlined that learning is one of the most important parts of BEV and HEV development.
“Therefore, every one of our prototype cars has an Internet address and we are reading out the load collectives for analysis," he reported. "This game will be won by whoever learns the fastest.”
During an extreme test, the carmaker demonstrated the potential of electro mobility. An electrically powered Mercedes-Benz A-Class E-Cell drove from Stuttgart to Monaco across the Alps within 2.5 days. “On average this BEV consumed a diesel equivalent of only 1.97 liters per 100 kilometers,” Schenk said.
The A-Class E-Cell is powered by an electric engine with 50 kW (70 kW peak) and 290 N·m (214 lb·ft) nominal torque. The electric motor is supplied with energy from a liquid-cooled 36 kW·h lithium ion battery. Daimler rates the range at more than 200 km (124 mi). Series production of 500 units started in 2010.
Dr. Ing. Stefan Kampmann, member of the divisional board of Bosch gasoline systems, electric vehicles, and hybrid systems, reported on a mixture of psychological findings and market dynamics. Under the heading “Lessons Learned,” he said that according to a customer survey and market feedback, “Electric driving is not about CO2. It is about fun."
Dr. Kampmann noted that from the survey, Bosch learned that people ultimately prefer plug-in hybrids because they want mobility without compromise. "Electric driving generates initial fun. However, when the drivers realized the limitations of a BEV, they opted for PHEV vehicles,” he said.
Electric bikes are cool
A growing market for Bosch electric motors and Li-ion batteries is electric bicycles (pedelecs). During the 18 months the supplier has been serving this market, the image of pedelecs drastically changed from what the supplier initially expected it to be. At first, the technology was considered mainly to be a great help for people who find riding a standard bicycle too much of a physical effort. Now, pedelecs are "cool, fancy, and stylish, and they are bought by young drivers,” Dr. Kampmann noted.
Commenting on results from an e-mobility solution currently under test in Singapore, he said there is “a business eco-system developing around our open platform with a level of creativity we cannot imagine.”
Hans-Jürgen Schneider of ZF Friedrichshafen highlighted the constant increase of electric traction power in the BEV. “Initially we were working with 15 kW," he explained. "Today we have reached 35 kW of power and we will soon be handling 75 to 80 kW.”
In a byline he added something that was quite remarkable for a national market desperately seeking well-trained engineers: “The green image of this topic attracts motivated young engineers.”