A technology ahead of its time: the emerging world of flow batteries, page-17

In the 2013 document, there's an explosion diagram of "Gen 3 tank with Gen 2.5 stack exploded". There's also a separate drawing of a "Gen 3 stack" which looks not dissimilar to the stack on the Gen 3 battery just announced. So it seems to me that the product that was actually introduced back then was the "Gen 3 tank with Gen 2.5 stack", and that Redflow now refers to this as the "Gen 2.5 battery". The Gen 3 battery just announced has a totally new design (??Gen 4 tanks??), but the electrode stack looks more similar to the "Gen 3 stack" depicted in the 2013 document.

By the way, it has been explained to me that the current battery stack is actually 2 5kWh battery stacks bolted together, and that's certainly what the "Gen 2.5 stack" depicted in the document looks like.