Probably never. This isn't a dumb question like the guy above made it seem. They would just release a battery with a case that would devoid the protection that the device receives from the back cover. Which still wouldn't be too bad, considering you'd still have the shock proof, dust proof, and "water resistant" front (I say that, because now the back isn't). It also probably won't ever come out, because very seldom few people like you and I would like a huge battery for the Active, as the only way to do that would really be to lose water proof capabilities. Which is the main reason why people got the phone. So, it's just not a money maker if they did. They might sell ten or maybe even 100, but not enough to spend the money to develop it and produce it.