Fairly linear, but it stays on 100 for quite a long time, I rang up apple today though and I've got an appointment on Monday to get a free replacement phone, the guy i spoke to said that it wasn't something that he had encountered before

Over the last few days, every time my iPhone 4 gets down to around 20%, usually just above, it suddenly closes the application I'm on, flashes that it's at 1% battery and turns off. I then put it on charge and starts at 20% again. It's happened 3 times in the last two days, I've tried a soft...