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Need a backup battery for trips into the backcountry? The Sherpa 15 is an ideal choice to keep your devices going for days between plug-ins. With a capacity of 3,870 mAh it’s got more than enough juice to fully charge an iPhone 12, with enough left over to add some power to your GPS unit, headlamp, or smartwatch. (Bonus: It has both a lightning cable and a micro-USB cable built in.) Weighing just 4.6 ounces, the Sherpa 15 also has a slim profile that you can slip into nooks and crannies of your pack. Score it now at REI for 50 percent off its $49.95 list price, making it $24.73.