OK, in that case to me it looks like a tiny scratch, not even all the way through. It should be fine for now, but keep an eye on it and you swap it in and out for signs of further deterioration. Is that at the top or bottom of the battery? If the top be a bit more weary, if the bottom then it should be fine. The bottom of the battery is grounded to the whole chassis of the
mod anyway. If the top shorts to the chassis then that is where the problems come in.