If you’re into technology, chances are your list of basic human necessities has one more thing on it after food, water, and air: extra battery power for your gadgets. Every device, whether it’s a smartphone, tablet, laptop, mouse, or Bluetooth headphones, needs power to keep going, and we’re not always near power outlets when we need them. That’s where a portable charger comes in handy.

Portable chargers, sometimes called power banks, are standalone batteries designed to recharge your gear. These small, black, nondescript boxes with USB ports might not look like much, but they can carry enough extra power to recharge a laptop several times over. There’s no way around it: if you regularly carry a lot of devices with you and want them to make it through the whole day, you need a portable charger.

The portable charger market is full of different models, ranging from keychain-size tubes with just enough to refill your phone to capacious models that can charge several devices at once. Picking the right one is a matter of knowing your needs and the best models available, and our shopping guide covers both, so let’s get started.