Put an extended battery in my galaxy S3. Let's forever now. Original 2200 mah lasted me until lunch everyday. Got a 3200 mah, lasted me until end of work, and I would have to charge it in the car on the way home. But took the regular back. But if I was waiting and playing games or something, it still would go really. So hot a 5800 mah, had to get an extended back and case, so it is heavier and thicker, but I only use about 50% s day now. Totally worth it to me. 4951
@mpjp0907: I think it was about $18 for the battery, phone back and silicon TPE caseFrom eBayAmazon has some also, but not the 5800 mah, not sure about S4 4951