One of the reasons I purchased the S4 was the ability to have a removable battery. I have installed an Anker 5200 Mah battery in the S4. It comes with a removable back cover in either black or white. My S4 is white and the new white back cover is a very nice fit. Of course it makes the phone bulge somewhat and it is heavier, but you can get use to it very quickly when you never, ever have to look at the battery percentage and worry if you can get through a long day. I have used Anker products before and they are pretty good. The battery is warranteed for 18 months. If you can get used to the extra weight it's pretty nice. I ordered a extended battery TPU case from Hyperion that fits it nicely.