Researchers in Germany have developed software that checks the inside of used electric vehicle batteries with X-rays, without opening them. The work, from the Fraunhofer Institute for Integrated Circuits IIS and Hochschule München, aims to make it easier to decide whether an old battery is safe to use again. If the method works at scale, more batteries could move into home and grid energy storage instead of going straight to recycling.
The software is part of a project called AIR. It reads 2D X-ray images of a sealed battery pack and looks for signs of physical damage. These include cells that have moved out of place, cells that have bent out of shape and cells that have swollen. Fraunhofer says it works with the three main cell types used in electric cars: cylindrical, prismatic and pouch cells.
Why a battery's health is only half the story
When an electric car battery reaches the end of its life in a vehicle, it often still holds a useful amount of charge. A battery that no longer gives a car enough range can still store energy for a home, a business or the electricity grid. Fraunhofer notes that this kind of reuse can save resources and lower carbon dioxide emissions.
The difficulty is knowing which batteries are safe to reuse. At present, the main measure is the battery's State of Health, a figure that describes its electrical and chemical condition. It shows how much energy the battery can still store, but not whether anything inside it is physically damaged.
That physical condition matters. Fraunhofer points out that ageing, vibration, accidents and deformation can all affect battery cells and modules, and may have safety consequences. Until now, these problems have been hard to check in a closed battery pack without taking it apart. Opening a pack takes time, needs trained staff and carries its own risks.
How the scanner works
The AIR system is a scanning line. Either a battery pack or a whole car moves through a narrow X-ray beam. A source above sends the beam down through the battery, and a detector below captures the image. Fraunhofer compares the setup to a car wash.
Software then analyses the images automatically. It finds each cell and checks its position and shape against what it should look like. In the test environment, checking one battery pack takes about five minutes. Fraunhofer says the real time depends on the size of the pack, the setup and the number of images taken.
Fraunhofer first presented the AIR scanner in 2024, when more than 100 private car owners took part in a pilot project. The new step is the software that reads the images on its own, which removes much of the manual work.
Testing on crashed cars
The researchers test the system on a VW ID.3 that has been through a laboratory crash test at DEKRA, a vehicle testing organisation. In that test, the car hits the back of a stationary VW Tiguan at 79 km/h. The front of the ID.3 is badly damaged.
The X-ray scans of the battery under the car show no safety-critical damage. All nine battery modules have a regular cell layout, with no overlapping or bulging cells. After electrical tests and other checks, the battery receives EUCAR Hazard Level 0, the lowest rating on a safety scale used by the car industry. It is judged fit for continued use.
A second test gives a different result. In a crashed battery made of cylindrical cells, the software finds an area where several cells have moved out of place. There is no sign of swelling, but the researchers do not recommend further use because of the clear damage.
Together, the two cases show what the system is for: separating batteries that can keep working from those that should go to recycling or careful storage.
Limits and next steps
Fraunhofer is clear that the X-ray check does not work alone. The findings are one part of a wider assessment and do not replace electrical testing or safety checks for each case. The crash results also come from individual case studies rather than large trials, so wider testing is still needed.
The institute suggests the technology may also play a role in future regular inspections of electric vehicles, although it presents this as a possibility rather than a plan. It is also preparing a larger system, called Giant-Eye, at its X-ray technology centre in Fürth. This is expected to allow three-dimensional scans of complete vehicles.
For now, the work addresses a practical gap. As more electric cars reach the end of their life on the road, the question of what happens to their batteries becomes more pressing. A fast way to see inside a sealed pack could help more of them find a safe second use.
