If you want to effectively double the battery life of your phone, this is a great S5 battery case to consider. (heavy.com)
According to the manufacturer you can get at least double the battery life of your phone with this case attached, and it's one of the more impressive Android options out there. (t3.com)
In addition to virtually doubling the battery life available on one charge cycle, the new juice pack air is also designed to maximize the user experience. (ecoustics.com)