Gear Review: Mophie Juice Pack Reserve

Stay connected with this keychain-size battery charger.

Don’t underestimate the strength of this keychain-size charger. “It revived a dying iPhone, doubling—and sometimes tripling—my battery life,” reports one tester who used the Reserve to map dayhikes in Sequoia and Redwood National Parks.

The budget-friendly, 1000mAh lithium-ion polymer battery connects to every generation of iPhone through a retractable 30-pin connector, and (according to the manufacturer) can be recharged with the included micro USB cable for more than 500 full cycles (roughly 12 years if you hike two times per week every May through September).

Bonus: The Reserve doubles as an LED flashlight. Bummer: USB wall charger ($29) not included. $40; 1.8 oz.;