Tablets typically have excellent battery life, but even eight or nine hours isn’t enough if you’re crunching quarterly sales numbers or planning PowerPoint decks on a cross-country flight, not to mention an intercontinental one. A portable external battery pack can keep you juiced up for your entire trip. However, just any old external battery pack won’t satisfy a power-hungry tablet. Luckily, these 10 tablet-optimized chargers promise to keep you working while far from an outlet. They'll also charge your smartphone, and some can even give your laptop a lift.