I'm picky when it comes to rechargeable battery cases, but after potting the new Jackery Leaf case through its paces for about a month, I'm a fan.
The first thing you will notice about the Jackery Leaf is that it is a two-part case.
You get the case and the battery. It all fits together very easily.
The case fits onto the battery pack and snaps in very securely. The battery pack is Apple- approved, and is a Lightning connector. (5S, 5C)
On the backside of the Leaf is a power button so you can check the battery. When you push the button, LED lights will illuminate either red, blue, or green depending on how much battery you have remaining. When it's flashing red, you have reached less than 10% of battery left to use.
When charging, you can charge either the iPhone or the Jackery Leaf first.
The Jackery Leaf charges fast. Faster than other rechargeable packs I have tried. It also has more capacity than a Mophie Juice Pack. It also costs less than the Mophie.
I recommend this case. It's thin, it's light, has a huge capacity, and it charges quickly. It's all you could ask for in a iPhone rechargeable battery pack , and it costs less than other well known brands and models.