The options are plentiful, and so are the price tags. The really nice battery cases for the iPhone cost well over $100 dollars.
As cases go, this 3,000mAh accessory battery case is really more like a back plate with a pretty thin profile, though that may appeal to some folks that like to keep their gear “naked.” This battery should provide several extra hours of talk time and video usage. Recharging is done through micro USB and should take less than four hours.
Like most battery cases, this one also has an LED battery level indicator. It is also available in three different colors, black, gray-ish blue and white. If you are looking for some affordable extra juice for your iPhone 5 or iPhone 5S, this thin case is on sale for one day only for $15 (see source link).
iPhone 5 and 5S battery case