These portable chargers and power banks give you the most boost when you're out of juice. I’m a Mobile Analyst at PCMag, which means I cover wireless phones, plans, tablets, ereaders ...

This is where a portable charger, battery pack, or power bank becomes invaluable. By connecting your phone to a portable charger, you can recharge your device without being tied to one location.

Some power banks ... on Qi chargers (7.5W) and Qi2 chargers (15W). Some battery makers have built Qi or MagSafe-compatible wireless charging into the surfaces of their portable batteries.