TÜV Rheinland and Twaice develop battery check for e-cars

TÜV Rheinland is also advancing the transformation of its inspection business and has now started development with the battery analysis specialist Twaice for a new service to evaluate traction batteries. The subsidiary Battery Quick Check GmbH will implement a service of the same name that allows traction batteries to be reliably assessed. "Currently, there is no market-ready service for business customers to evaluate used traction batteries—the most expensive single component of electric vehicles—across manufacturers and independently," says Matthias Schubert, Executive Vice President Mobility globally responsible for TÜV Rheinland's mobility business. Recently, however, the competitor GTÜ, together with the Austrian battery diagnostics specialist Aviloo, launched a similar service, which, however, involves an examination during the drive using a dongle installed by the user at the OBD.

At Standstill and During Charging

This should be different with the new offer. Testing is done while the vehicle is stationary and during the charging process, largely automated and with external hardware, so that other services can also be performed on the vehicle. Together with the technology partner Twaice, they aim to build the leading company for the independent evaluation of used traction batteries in the coming months. The Munich-based company offers specialized analytics software that optimizes both the development and operation of lithium-ion batteries. The new Battery Quick Check service will be available from autumn 2022, for example for car dealerships, workshop chains, logisticians, insurers, leasing companies, or fleet management of companies. Private customers can use the service through their car dealerships or workshops. The service includes a detailed report on the battery's condition (State of Health, SoH), certified by TÜV Rheinland. The headquarters of Battery Quick Check GmbH is in Cologne.

"We firmly believe that all market participants will benefit from greater transparency about the battery life of electric vehicles. Because it builds trust," says Stephan Rohr, founding partner and one of the managing directors of Twaice.

In recent years, comprehensive knowledge and technical know-how have been built on how to quickly and reliably determine the actual condition of traction batteries, Rohr advertises. Now, the urgently needed transparency is being brought to the market for used electric vehicles. He refers to a market survey from September 2020, in which more than 90 percent of electric vehicle users requested an independent battery assessment before deciding to purchase a used electric vehicle.

A system based on on-board diagnostics is being developed

For the Battery Quick Check, the cooperation partners use the on-board diagnostics system (OBD) with the OBD2 interface of a vehicle. Workshop personnel read out all relevant data from the interface in about 60 minutes. This data is then processed using battery analytics developed by the Munich-based company. The result is an independent condition report on the traction battery certified by TÜV Rheinland, which takes into account individual aging, beyond the algorithms of the vehicle manufacturer, which consider nominal capacities or calendar age.

The aging is influenced by driving behavior

The aging of the battery depends on many factors, such as how often fast charging is used, driving style, or how often it is charged to 100 percent, explains a Twaice expert. For driving behavior, a sporty-aggressive driving style with strong acceleration and infrequent regenerative braking leads to higher stress on the battery. For charging, frequent use of fast charging options also stresses the battery more. In contrast, a predictive driving style is gentle on battery aging—for example, by already planning the optimal charging method for later. 

Batteries also age differently calendrically

In calendar aging, various factors such as temperature and charge level influence the aging process, as the specialists describe. The "comfort temperature" of a lithium cell is around 20 degrees Celsius. If the cell is permanently stored at, for example, 30 degrees Celsius, it ages about twice as fast as at 20 degrees Celsius. The state of charge also influences calendar aging: Ideally, it is around 50 percent of the maximum capacity. Permanent storage at maximum charge level or at 0 percent charge level leads to a shortened lifespan. Based on all the data, a longevity prediction for the expected mileage of the battery is also targeted in the mid-term.

"Although electric vehicles themselves provide information about the battery condition, practice shows that the 'State of Health' supplied by the battery management system often diverges significantly from reality. Consequently, predictions about the further lifespan and performance of a traction battery are often inaccurate based on this," the providers explain the step. 

According to the partners, the actual remaining capacity cannot be reliably determined without an independent diagnosis of the traction batteries of electric vehicles.

The expected market volume is growing very dynamically

The certified Battery Quick Check can thus be included in the overall assessment of a used electric vehicle, as performed by TÜV Rheinland's experts in the Autoservices & Appraisals business area. An independent assessment of the 'State of Health' of the traction battery is central to determining the market price of a used electric vehicle, says Matthias Schubert. The new service is planned to be introduced in the German market from autumn 2022, initially with a double-digit number of vehicle models, which will continuously grow. Even Tesla models, which do not have an OBD interface, should be eligible for the service. Alternative analysis methods will be used for these, according to Twaice. The rollout in other European markets is then planned for 2023. The service price is not yet set. The partners expect that there will be a need for around 150,000 evaluations of traction batteries for electric vehicles in Germany alone in 2023.