The is one of the more stable, and diverse, portable chargers on the market. It can power iPhones and Androids at the same time with dual USB ports and is compatible with quick charge devices. On Amazon, if you put it into your cart and use special code Y18A1260 you will save $14, bringing the cost down from $50 to $36.
The Anker PowerCore II has enough capacity to charge an iPhone 7 fully 6 times over. With 4.7 stars out of 239 reviews, it's earned Amazon customers trust.