Unless you have a charging cord handy, a USB battery pack is basically just an expensive paperweight. Luckily, that’s never a problem with today’s deal.
The Jackery Bolt (pictured above) is a little expensive at $24 for 6,000mAh (with promo code BOLT6000), but it includes a built-in Lightning and microUSB cable, so you won’t have to worry about carrying a spare. If you’re the forgetful type, that’s well worth the price premium.