pv europe: What are the challenges in battery cells?
Herbert Schein: With all battery types it is the electrochemistry of the lithium batteries that is decisive, and often underestimated. Compared to the production of solar cells, the level of complexity is much greater. Producing solar cells much more depends on acquiring the right machine technology. That explains the rapid rise of the Chinese manufacturers, who built their success on German machines. In the battery sector things are a bit more complicated. Think of it this way: Imagine a battery cell as a component with 150 dials that you can change while you are making it. If you change one dial, that automatically changes many others along with it.
How are you dealing with this level of complexity?
With the cells that we produce here, we strive to control as much of the value chain as possible. For example, we design and build the most important machines ourselves. That is one of our core strengths and gives us an edge over our competition. We also do our own vocational training as well as training of engineers and computer technicians, in cooperation with local schools and universities, and also the Cooperative State University in Heidenheim.
Can you say more about that?
As I said, the electrochemistry requires a great deal of experience. We select a certain sample of cells from our production lines of Varta Storage in Ellwangen, which are then tested in very specific ways: some right away, some a few days or weeks later, and some even after a few months. These tests and the experience gained from them result in a data set that can tell us exactly how cells made with different formulas react. For example, a battery has changing properties when exposed to high temperatures for a long time. And if we want to build long-lasting batteries, we have to take that into account.
What characteristics does a energy storage system need to have?
It needs to have high energy density and great durability. It also needs to be robust and persevere under real-life conditions. We use our extensive know-how and experience with small cells and apply it also to our larger energy storage systems.
Interviewed by Heiko Schwarzburger
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