As I’ve learned from using Anker’s PowerCore Fusion, USB battery packs are way easier to keep charged when they can plug straight into the wall. This 9,000mAh model from RAVPower has folding prongs, and even a built-in Lightning cable for Apple devices, in addition to a USB port that can accept any cable. Get it for an all-time low $29 today with promo code KINJA056.