Agreed. But it is a functional battery more than it is "only a design"
Fair enough. Is a prototype flying car a design or a product? Can I get one -- not the design, the product?
Neither... it is a prototype. Somewhere between just a design and a product is a wide variety of other states. A single, physical item that actually functions as designed may not be a product yet (or ever) but it is leaps and bounds beyond "just a design." If "prototype" and "design" mean the same thing then a lot of people get that wrong everyday.