Battery Test for Electric Cars

Battery age is not only a function of linear time (calendar age) but also of the cycle of charging and discharging (cyclical age). As the battery ages, its capacity gradually decreases, affecting the vehicle’s range. Ageing of the traction battery of an electric car means deterioration of the battery’s characteristics. In addition to aging, high temperatures, overcharging (high voltage), deep discharging (low voltage), high charging current affect the EV battery State of Health and consequently its capacity.

The battery is the most expensive component in an electric car, which makes its State of Health (SoH)—defined as its remaining capacity—a crucial factor in determining the car’s value. The SoH decreases rapidly beginning at 70-80% of the battery’s initial capacity. With our battery test, the battery capacity can be accurately measured. This is great news for car dealerships and leasing companies as well as private individuals, because it provides the basis for more transparent sales negotiations. It also gives a clear and precise statement regarding the actual battery capacity and thus an indication of usability.

This solution offers fast and accurate results, delivered in minutes rather than hours, which is typical for other battery tests. Those lengthy procedures require the battery to be discharged or charged, while the DEKRA battery test does not. In fact, our test can be completed in approximately 15 minutes, and its accuracy has been validated by RWTH Aachen university as well as by various car manufacturers.

The car must be equipped with an On-Board Diagnostics Interface (OBDI) in order to connect with the mobile application via Vehicle Communication Interface (VCI). In addition, the battery must meet the following preconditions:

• State of Charge (SoC) around 40% – 80%.
• Battery temperature between +10°C and +30°C
• Individual cell temperature differences within the battery of <2°C

If these conditions are not met, an error message will appear. Finally, for the dynamic test, a space of 100 meters is necessary for acceleration.

The procedure is based on measuring various battery data such as currents and voltages under load, i.e. during a brief acceleration, via the VCI. The real know-how, however, is in classifying the values measured here. Behind the procedure is a highly complex, very elaborate database and a patented algorithm. The basic data is determined in advance for each individual vehicle type with measurements run under a wide range of conditions; this is followed by appropriate structuring and further complex calculations, in some cases with the aid of artificial intelligence. We refer to the entire process as "parameterization". The values measured in the test case are then evaluated based on these type-specific parameters.

The easy-to-read report contains the SoH value, OEM data, such as nominal capacity, cell voltage and cell current as well as more general information about the vehicle, such as model, vehicle ID number and mileage. The result is available immediately following the evaluation and can be sent to the user via email.

So far, we have parameterized a large number of models. Among them are models of various German and European manufacturers but also Asian makes. We are constantly working on further parameterizations. Since the parameterization process is very complex, we are initially concentrating on the vehicle models that are frequently used in a specific market or by specific customers.