What was the decisive reason for specializing in battery repair at the Hoyerswerda site?
In 2019, Leadec received an order for the pre-assembly of battery housings from a company in Kamenz. We looked around within a radius of 50 km and found a building in Hoyerswerda that was ideally suited for the high-voltage sector.
Since September 2022, we have been repairing high-voltage batteries from electric vans for a major car manufacturer, which come to us from all over Europe. This has allowed us to build up extensive experience in the field of battery repair and we are a pioneer in the repair of batteries on an industrial scale. If you would like to find out more, you are welcome to read our white paper “The repair of lithium-ion batteries” to read more.
Saxony has now developed into a real hotspot for electromobility, with many exciting companies and initiatives. And it is easy to find qualified personnel in this region.
In which areas of application are repaired batteries typically used and how long do you know from experience that they are still in operation?
Once the cause of a fault has been identified, the decision on further use is made on the basis of a profitability test. Decisive factors are the repair costs, the spare parts costs and the remaining load capacity of the modules. For further use in the vehicle, at least 80 percent of the charging capacity must be restored after the repair. Of the batteries we have repaired since 2022, all are still in use and we assume that they can be used for several more years.
If a battery no longer reaches 80 percent charging capacity, reuse applications remain. The use of automotive batteries or modules as storage in the energy sector is well established, for example to compensate for grid fluctuations as intermediate storage.
Which fault patterns do you encounter most frequently when repairing batteries?
Leadec repairs batteries that come to Hoyerswerda from all over Europe. When they have to be returned to the vehicle, there are only 72 hours in total for transportation and repair. The number of repairs increases with the number of registrations, but overall the batteries are proving to be very robust.
We currently have around 230 known battery-specific fault patterns. The data analysis shows that in the past, electrical and electronic faults accounted for the majority of repairs. Contactors, for example, fail very frequently, presumably due to the high current load on the contacts. Another frequent cause of faults are loose plug connections. It remains to be seen how the electrochemical components — i.e. modules and cells — will behave in the medium to long term.
How does a typical repair work — from diagnosis to end-of-line testing?
The fault analysis and determination of the cause take place in two stages. First, a visual inspection of the vehicle battery is carried out to detect external damage, coolant leaks or similar. If no external damage is visible, the complete fault diagnosis and analysis follow.
The battery is then opened. To do this, the coolant must first be drained and the corrosion protection on the screw connections of the housing removed. Cooling the battery down to ‑20 °C makes it easier to remove. Once the vehicle battery is open, all components are visually inspected again and the contactor, wiring and busbars are checked.
Depending on the result of the fault diagnosis, the defective components are then replaced, for example the BMS, current sensors or modules. Defective cells can be replaced at module or cell level, for both hard case and pouch cell types.
After replacing the defective components, all electrical connections are restored. The screw connections are then refitted and the housing is filled with coolant. The leak test is carried out by blowing in forming gas and then carrying out a sniffer probe test to reliably locate any leaks.
If this test is successful, the corrosion protection is applied to the screw connections and the battery undergoes the final end-of-line test. The entire repair process is fully documented for later traceability — from delivery, fault diagnosis and repair through to the final test and dispatch.
How do you ensure that a repaired memory works reliably in the long term, even if the original defect is initially deemed to have been rectified? Are there measures in place for tracking during operation?
Leadec uses software developed in-house for documentation. All relevant battery and test data is stored in this for each repair process. This includes the battery ID and determined error codes, test logs and photos of incoming goods and all damage. At the same time, all defective and new parts are comprehensively documented. The torque values of the screw connections and the results of the leak test are also included in the documentation. Finally, the end-of-line test is carried out in accordance with the manufacturer’s specifications, after which the BMS takes over again. So far, we are not aware of any failures in repaired storage tanks.
What role does the operating data provided by the BMS play in fault diagnosis and how well can it be used to systematically detect faults?
The BMS knows everything: current, voltage, temperature, number of charging cycles and many other things. The informative value of this data is very high. With a probability of around 80%, the BMS data can be used to determine which fault is present if the relevant expertise is available. With the other batteries, either the BMS is unresponsive or further diagnostics are required to detect a faulty sensor, for example.
Both digital measurement technology for all battery types and diagnostic devices from battery manufacturers are used to obtain a complete fault pattern. The results are used to create battery-specific fault pattern catalogs, which are used for comparison in further analyses and are continuously updated.
Do you see potential in deeper analytics, e.g. at cell or module level, in order to make more precise statements or recognize recurring error patterns?
During fault diagnosis, the battery can be analyzed down to cell level in terms of voltage, current, capacity and temperature. This data can be used to decide on further use in the vehicle or in second-life applications. In addition, a predictive recommendation to replace certain modules that will soon reach their performance limits is possible as part of the repair. This reduces the need for follow-up repairs.
There are various approaches for looking inside cells: Impedance spectrography, tomography or X‑ray. These methods are used when the condition of the cell cannot be assessed from the data. They can be used, for example, to detect dentrids or to clarify why a resistance has changed.
We see great potential for estimating maintenance measures in the future and for preventive maintenance. There will be an increasing need for this, especially for stationary electricity storage systems.
Where do you currently see the biggest challenges in battery repair?
The number of e‑cars on the roads is developing more slowly than expected, while at the same time batteries are lasting much longer than many experts predicted. This combination means that the number of repairs is still quite low.
During the repair itself, the structure of the batteries sometimes causes problems, this is particularly the case with older batteries. Their design makes repair practically impossible, as components can no longer be reused after the battery has been opened due to gluing, for example.
How important is continuous monitoring after the repair for you, especially with regard to safety, performance and complaints?
It would be very interesting for us to have the lifetime data of a battery in order to derive preventive maintenance measures. This is particularly important for stationary storage systems. An important indicator is continuous temperature monitoring, for example, also with regard to safety.
You have already gained experience with the NOVUM Battery Analyzer. What particularly impressed you? And where could you see the Analyzer being used even more in the future?
NOVUM has many years of experience with test systems. We were particularly impressed by the ease of use, which is a decisive factor for our employees. Just one mouse click — the system does the rest. Thanks to AI, it’s also very fast, so we get an accurate picture of the current battery status in no time at all. We would like to use the test stand even more often if there are corresponding projects.
