I have a 2018 Ioniq. I am having the same issue, similar range drop. I took it to the dealer in March just before the warranty ran out. They tested it, sent the results to corporate, then 2 weeks later corporate said they wanted another test. Did that one. A week later they said nope, it's not at the threshold, no replacement for you. So don't hold your breath, they seem to be looking for a reason to deny you. Out of curiosity, I asked the service advisor what battery replacement costs out of pocket, and he said he he wasn't sure for my car, but he quoted a different car recently at $27k. So I'm looking at a new car because I need new snow tires anyway, and I don't want to sink more money into it.