Massive power: Best of the biggest power banks and portable battery packs

Remember walkmans? They sparked quite a revolution back in the day by letting us listen to our super awesome megamix tapes even while on the go. Most walkman models ran on a couple of AA batteries which could be easily replaced when exhausted.

Smartphone batteries, however, are a bit different from garden variety AA cells. They have to be recharged regularly, and there's not always a power outlet nearby. The solution? Get a power bank! These portable battery packs are extremely convenient as they provide emergency power when we need it. And while they come in a broad range of sizes, today we'll focus on the largest among them.

In the slideshow below we've put together a bunch of super-sized power banks – the kind you'd want to have in your backpack while traveling. These are large enough to recharge a smartphone multiple times, while their multiple USB outputs allow you to recharge a couple of devices simultaneously. Check them out!