Your phone does a lot of jobs on a backpacking trip. It's the map, the camera, the GPS track, sometimes the headlamp charger and, on a clear ridge, the only way to text home. A dead phone on day three is an inconvenience at best. That's why a power bank is one of the most common gadgets on a multi-day trip.
The trouble is that many power banks are sold to commuters. The listings brag about how fast they top up a laptop, and few of them tell you what you care about on a trail: how many phone charges you get per ounce, and whether the thing survives a rainstorm in a hipbelt pocket.
The eight below are ranked on those two things first: usable energy for the weight, and how much rain and knocking around each one takes. Ports and recharge speed come after that. My dad and I haven't bench-tested them. The order comes from each maker's specs, CleverHiker's power bank roundup, and what Amazon buyers report in their ratings and reviews.
One note on scope. Beyond a certain size a power bank turns into a laptop battery or a camp power station, which weighs pounds and rarely belongs on a trail. The Goal Zero here is about as far up that ladder as a backpacker should go.
