All phone batteries have one thing in common: They die. Sure, Apple Inc.’s iPhone 13 Pro can last for roughly 15 hours of typical browsing, about the same as Samsung Electronic Co.’s Galaxy S22+ Ultra, according to tests by the specifications experts at PhoneArena. But at some point—usually when you’re the farthest from a wall outlet—the electrons stop ricocheting and the screen goes dark. For people on the go, a portable charger such as Belkin’s $70 Boost Charge Plus remains an essential accessory. It’s just 2.9 inches wide and less than an inch thick, and it weighs a mere 8 ounces, with enough juice to give you an extra 31 hours on your phone—plus it has a snazzy blue cover.