Apple did tell us the new iPhone 5S and 5C do have a bigger and better battery, but honestly the batteries aren’t all that great from the current iPhone 5. I don’t think there will be any big difference. This is the quote which Brian Klug of AnandTech said –
“While poking through the FCC documents and piecing together a story on the network band situation for the iPhone 5S and 5C, I remembered that part of a normal disclosure is in fact battery size. Apple noted the battery on the iPhone 5C increased, and I’ve been curious about the 5S battery size as well given the different PCB photos with slightly changed aspect ratio that floated around as potential candidates for the 5S. Apple also doesn’t disclose the battery size in Whr or mAh on their tech spec pages, making this the only real place to find out outside of opening them up and looking once they’re available.”
The iPhone 5 has a battery capacity of 1440mAh, the 5C is only slightly increased at 1507mAh and the 5S is further increased to 1570mAh, nothing great compared to the competition…
Also keep in mind, this information comes from FCC documents, and not Apple themselves, but i doubt these documents would lie.. What do you say?