(Image credit: Tom's Guide) Even devices with the best phone battery life will ultimately run out of juice. That’s why the best power banks exist to provide a charge while on the go, especially when you’re nowhere near an outlet. We bought five top-rated power banks on Amazon under $20 to see if they’re worth it, from brands you probably never heard of. Our testing ranged from the Amazon Basics option to one that offers the convenience of MagSafe , all to see how well they charge an iPhone. Personally, I prefer a charger that provides a significant amount of power in the shortest time possible. Below, I’ll break down the details, including how long they take to recharge and the unique features that come with them. Here’s what I found. Are $20 Portable Chargers a Steal or a Scam? | Value Verified - YouTube Watch On How We Tested For this roundup, we’re grading each power bank in three categories, with each receiving a score from 1 to 5.…