In December 2015, Apple released their first official Battery Case. It was released for the iPhone 6S and 6 in charcoal and white, and then later extended to the iPhone 7, along with a new color, red, just for the iPhone 7. Full review and thoughts below.
Colors: iPhone 6S: Charcoal Gray and White iPhone 7: Black, White, and (PRODUCT)RED
Charging: Charging for the Battery Case is very simple. You just place your phone in, and plug the in the Battery Case in with a lighting cable. It charges the phone halfway, then the case fully, then the phone. You will know if the case is charging by a little light on the inside. The only problem I have is that sometimes it doesn't charge the phone, but this is very rare, and only happens because I bought used one.
Price: Its $99, which is around what other battery cases cost.
Overall, the Battery Case is very awesome, and I get around a 12 hour battery life, which is amazing. I really think that this is a great investment, and its cool because you can also see the percentage of the case in iOS.