Charge your phones for nearly a week or any other USB device with this super handy Dark Energy Reservoir. The size of this massively powerful charger is a slight larger than the iPhone 5 but it comes loaded with an 8,000 mAh battery. Since the reservoir has been equipped with the pass-through technology, it will allow you to charge devices even when the Reservoir is attached to an outlet. It can retain its charge for one full year and can also charge two devices simultaneously. So if you are in desperate need of a power backup for your smart devices, this reservoir is indeed a worthy choice to make.