News - General T&M

Standard to determine range of e-cars

16 December 2010 - TÜV SÜD has developed a standard for determining the range of electrically powered cars. The special-interest magazine "auto motor und sport" used the TÜV SÜD E-Car Cycle (TSECC) in a major comparative test for the first time. The result of the test underlines that for example, the ranges determined in the comparative test under standard conditions (23 degrees) and wintry conditions (-7 degrees) differed by over 50 per cent.

While motorists in a representative survey of TÜV SÜD presented at the AMI 2009 were basically open-minded and showed a positive attitude towards electromobility, 36 per cent of respondents said that they would only consider buying an electrically-powered car if a range of 300 km was guaranteed, and 23 per cent were unwilling to accept a shorter range than comparable petrol/diesel vehicles.

In view of the current state of development of battery systems, a similar range to that of petrol/diesel cars appears unrealistic in the near future. According to the manufacturers, the ranges of all e-cars currently sold on the market, such as the Mitsubishi iMIEV, are roughly 140 kilometres.

"In view of these relatively short ranges, it is of paramount importance to give motorists precise information on how far they will actually get in their electric cars. In addition, the range should be measured not only in sunny weather at temperatures of 23°C, but also at wintry temperatures or if the heating in the car is on. Motorists will only accept these short ranges if they can rest assured that their electric cars will reliably take them to their destinations", emphasizes Dr Ralf Giere, CEO of TÜV SÜD Automotive GmbH.

Strong focus on realistic conditions

Based on the awareness that range is of major importance, the TÜV SÜD experts at the Heimsheim-based exhaust-gas laboratory under the leadership of Richard Trücher developed a standard for determining the range of electric cars. As key criteria, the driving style and the selected route must be as realistic as possible. The standard also includes measurement of the range under difficult conditions, i.e. at low temperatures or when secondary power consumers such heating are in operation.

Based on these objectives, the TÜV SÜD experts developed the TÜV SÜD E-Car Cycle on the assumption of an average speed of 60 km/h, 60 minutes of driving and a distance of 60 kilometres covered in a combination of country road, clearway, motorway and urban traffic. "When defining the test cycle we focused on short distances and city driving, which is the most likely use for electric vehicles. We also considered it important to map the driving style as realistically as possible. Given this, we chose an average speed of 60 kilometres per hour, a speed that is significantly higher than the roughly 34 km/h specified by the NEDC (New European Driving Cycle)", explains Richard Trücher, head of the TÜV SÜD exhaust-gas laboratory. To implement the test, the team first digitized test routes with the required test profile and tested them on a test rig under exactly reproducible conditions.

Impacts of weather on range were stronger than expected

However, the most exciting question was how changes in weather conditions and the associated operation of secondary power consumers, e. g. the air-conditioning system, would influence the range. The TÜV SÜD E-Car Standard answers this question, as the defined test cycle is also performed both at a wintry -7°C and with the air-conditioning system in operation.

The comparative test carried out by special-interest magazine auto motor und sport on the basis of TÜV SÜD's test standard for determining range delivered dramatic results. To take the Mitsubishi iMIEV as an example, while the range of the Japanese e-car determined in accordance with the legal test cycle defined in ECE-R101 at 23°C and without additional power consumption amounts to 133 kilometres, it is only 113 kilometres when based on the TSECC (carried out also at 23 degrees, but at a higher speed). At a temperature of -7 degrees and when additional power consumers are turned on, the range drops to a meagre 64 kilometres.

According to the test cycles driven in accordance with the TÜV SÜD E-Car Standard, the average range of the Mitsubishi e-car is 110 kilometers. "However, the average range has limited informative value for motorists. The TSECC established that weather conditions and the operation of secondary power consumers have an enormous impact on the range of today's electrically-powered vehicles. With a view to generating consumer confidence, we consider it important in this early phase of the e-car to inform motorists as precisely as possible about the range of e-cars under admittedly non-ideal, but very realistic conditions", underlines Dr Giere.

www.tuev-sued.de

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