While there are a good few smartphones out there with amazing battery life, there are many that could be better. This is where external battery packs come in very, very useful, like this deal on the RAV Power 3rd Gen Deluxe External battery pack. It carries a 15,000mAh battery capacity, and it has two USB charging ports so you can juice up two devices at once, and it comes with two USB cables so you don't need to provide your own. The status LED's keep you up to speed on how much battery life is left in the power bank, and it charges at speeds of up to 4 amps. It also has a security protocol in place that shuts the power bank down in case of a short circuit that happens while the unit is charging a device. you can grab the RAV Power 3rd Gen Deluxe battery pack on Amazon for a deal price of just $38.99.