Electric vehicles with mixed results at periodic technical inspections

Special evaluation of the "TÜV Report 2023" for the BMW i3, Nissan Leaf, Renault Zoe and Tesla Model 3. The main defects are brakes, low beam and axle suspensions. The TÜV Association calls for additional inspection points for electric vehicles at periodic technical inspections.

© Maxim Hopman via unsplash

Berlin, 11 April 2023 - Electric vehicles perform very differently in their first periodic technical inspection (PTI) depending on the model. This is shown by a special evaluation of the current TÜV Report of the four particularly popular e-models BMW i3, Nissan Leaf (ZE1), Renault Zoe and Tesla Model 3. "With the increasing sales figures of the past few years, more and more electric vehicles are turning up at the TÜV inspection centres. This allows us to evaluate the technical safety of selected electric vehicles," says Dr Joachim Bühler, Managing Director of the TÜV Association. With the Renault Zoe, an electric vehicle has made it into the "TÜV Report 2023" for the first time thanks to sufficiently high numbers. The report includes the results of 9.6 million general inspections. In the class of 2 to 3 year old vehicles, 5.3 percent fail the PTI with "significant defects" and have to be presented again after repair. The Renault Zoe's failure rate of 5.3 percent is exactly in line with the average of the 130 passenger cars tested in this age category. The Zoe's front axle suspension is the biggest focus of defects. Wishbones, track rods and coupling rods are particularly conspicuous. The function of the foot brake is also criticised more often than average. "Defects in the brakes occur with above-average frequency within all electric vehicles examined," says Bühler. One reason for this is recuperation, which is used to recover braking energy in electric cars. It relieves the brakes, which, depending on the driving style, can lead to the brake pads "falling asleep" (lowering of the coefficient of friction). "Electric vehicle car drivers should regularly brake hard to regenerate the brake pads and thus maintain full braking power," advises Bühler. 

The Nissan Leaf performs better than average with a defect rate of 4.3 percent. The Japanese car's dipped headlights and brake discs are conspicuous. With this result, the Leaf ranks in the upper third of the ranking for 2 to 3 year old vehicles. In contrast, the BMW i3 lands in the bottom third with a fail rate of 5.9 per cent. As with the Leaf, the i3's dipped headlights and brake discs are the most frequently criticised by the experts during the inspection. Last in line is the Tesla Model 3, which is one of the most popular electric vehicles in Germany. 8.9 percent of the vehicles inspected failed their first PTI. This would leave only four cars behind the Tesla in the ranking of this age group, including the Dacia Logan, Dacia Dokker and VW Sharan. In addition to the lighting, with defects in the low beam and fog lights, the Model 3's brake discs also have more frequent defects than the average of all vehicles examined. The same applies to the axle suspension. "Many electric vehicles are heavier than comparable models with combustion engines due to the battery. This often puts a particular strain on the axle suspensions," says Bühler. Even older electric vehicles have no particular problems with the issue of rust. 

The TÜV organisations inspect electric vehicles on the basis of the PTI Directive and type-specific inspection specifications. The focus is on the condition of the high-voltage battery, the electrical cables and the plugs. Among other things, the fastening, insulation and cooling of the power storage units are tested. "However, the high-voltage batteries of electric cars have so far only been subjected to a visual inspection. That is not enough," says Bühler. The PTI regulations would have to be supplemented with further specific inspection points for the safety of electric vehicles. "The high-voltage battery must be assessable over the entire life cycle of the electric vehicle. For this, the assessment organisations need access to the data of the battery management system," says Bühler. In addition, the high-voltage safety of the electric vehicle would have to be checked in general. Within the framework of the PTI, this could be implemented by measuring the insulation resistance and the potential equalisation in the entire high-voltage system. Another problem is the increasing encapsulation of the underbody of electric vehicles, which prevents a visual inspection of both the live high-voltage cables and the brake lines. Adaptations of the type approval regulations are required here, which, for example, prescribe appropriate inspection flaps in the panelling for a visual inspection of the safety-relevant components for the PTI. 

Methodology note: For the TÜV Report 2023, around 9.6 million main inspections of passenger cars were evaluated, which were carried out from July 2021 to June 2022. This guide published by TÜV and AutoBild shows 226 vehicle models in 5 age categories. In the ranking of 2 to 3 year old passenger cars, 130 types are listed. With the exception of the Renault Zoe, the electric vehicles considered are not yet included in the TÜV report because the number of vehicles tested does not yet allow for an in-depth analysis of the individual models.