This test is useful for those who want to buy a used electric car to determine if the battery is faulty or damaged, as well as for sellers to get a better price when selling their electric cars. Tziazzius, an expert from the Dekra inspection authority, noted that a good battery condition is between 80 and 100%, but even if the battery drops to 75%, there is no need to worry. Although the range will not be the same as the original value, the car can continue to be used effectively in city traffic. Checking the battery condition is also useful if one decides to drive an electric car for a long period. Expert Shabus confirmed that a battery condition test shows early indicators of the remaining battery life, which helps avoid more costly repairs. A high battery condition value indicates that it is in good condition, which significantly affects the range, a decisive factor in the value of an electric car. Therefore, the importance of these tests increases in the used car market. Fogt emphasized that «a battery condition test is very useful, especially for older cars, 7 or 8 years old, as the battery warranty granted by many car manufacturers expires during this period». If this value decreases, it means a reduction in the distance that can be covered on a single charge. There are two main metrics that play a crucial role in determining battery condition: battery capacity, i.e., the stored energy, and the internal resistance of the battery, which indicates the amount of energy loss inside the battery. However, there are no unified standards or a specific measurement procedure to determine the battery's State of Health (SoH), and therefore the battery's own value cannot be compared to the WLTP range. Fogt explained: «Each car manufacturer defines this value differently in its warranty terms, which complicates the matter for the end customer». Currently, there are two main methods for determining battery condition. In a power analysis, the amount of energy that can be extracted is measured. In this case, the battery is fully charged, and then the car is driven until the battery is almost completely discharged, after which the company calculates the SoH value using algorithms. Another method is to measure the internal resistance of the battery, which requires a short acceleration. If the resistance is high, it indicates a greater voltage drop and heat generation, which leads to a decrease in the usable battery capacity. In addition, some car manufacturers provide the ability to assess the battery condition directly through the Battery Management System (BMS). German expert Fogt considers this method less reliable because the SoH value is estimated by the BMS itself. The German expert added: «In all measurement methods, battery condition testing companies reach a dataset from car models, so that the measured values can be compared with the values of new cars». One can have battery condition tests performed at many repair shops, testing authorities, and car clubs, and the cost varies depending on the choice of test type, whether it is a quick test or a premium version. Quick tests are usually performed when the car is stationary, while more comprehensive battery condition checks last a day or several days with the car in operation. The Dekra inspection authority focuses primarily on measuring the internal resistance of the battery in its tests. Michel Tziazzius from the German inspection authority said: «This inspection method is done by quickly loading the battery; data is collected by accelerating the car for about 100 meters». He added: «We compensate for these effects through internal resistance, and a power analysis of the battery condition provides higher accuracy regarding the current range». Frequent fast charging and severe acceleration, especially when the battery is not at operating temperature, usually lead to battery aging. Shabus explained: «It is best to perform a battery condition test that analyzes the cell level if the range suddenly and rapidly decreases; a battery condition test can reveal a fault in it». He confirmed that combining the two methods will cover most needs: «After that, the measurement data recorded for each car model or battery type are compared with the parameters stored in cloud computing services, and the algorithms finally calculate the battery's State of Health (SoH) as a percentage». The Austrian company Aviloo, specializing in battery fault diagnostics, relies on power analysis in its battery condition test. Depending on the type of fault, it is not necessary to replace the entire battery if the problem can be solved by battery balancing. In addition, the German inspection authority is developing a second method in which the car's battery is charged for a short period. Even if only one cell in the battery is weak, it will affect the entire system. When buying a used car with a gasoline or diesel engine, one usually relies on some factors to assess the car's condition before purchase, such as reading the odometer, checking for any oil leaks, reviewing the timing belt's condition, and engine sounds can indicate the car's condition. However, with electric models, there are no worn valves or faulty clutches, and the battery is the most critical inspection point. But the problem is that one cannot determine the health of the battery in a used electric car just by looking at it or listening to its sounds. This is where the importance of what is known as a battery State of Health (SoH) test comes in, which is the primary metric for evaluating the most expensive component in the car. Matthias Fogt, an electric car expert from the German ADAC automobile club, said: «The SoH abbreviation stands for the battery's state of health, which is usually expressed as a percentage». He added: «Battery condition (SoH) describes the ratio of the current battery capacity to its original capacity. When the value is 100%, it means the battery can store the same amount of energy as it did on the first day of operation». Patrick Shabus from Aviloo explained: «This test requires an additional determination of the battery's internal resistance, and there are several factors, such as cold and heat and driving style, that greatly affect the result».
