The Jackery Bolt 6,000 mAh External Battery Charger with Built - in lightning and Micro USB Cables is the best external battery pack you can buy if you have an iPhone. (businessinsider.com)
Rechargeable Phone Case: While I love the above external battery chargers and always bring them on our camping trips, having a phone case with a built - in external battery means I'll never be caught with a dead phone battery. (ordinarytraveler.com)
Hiwill Solar Charger 12000mah, Waterproof IP67 Portable Solar Phone Charger, Dual USB Solar Power Bank Input 2.0 A MAX External Battery Charger with 2 LED Flashlight for Outdoors - with SoS Modes (amazon.com)