Portable devices like smartphones, tablets and iPods are equipped with built-in rechargeable batteries that always seem to need recharging at the worst moment. When that happens, the search for power can become desperate. Visit any airport terminal or similar venue and you are sure to see masses of power-starved devices -- and their owners -- huddled around every available electrical outlet.
Also called external battery packs, power packs and external power supplies, portable chargers eliminate the need to find an outlet while you're on the go. The most powerful portable chargers typically cost from $50 to $100, but models tailored for smartphones and MP3 players are also available for $30 or less.
Portable chargers are lighter, smaller and more ruggedly built than ever before. External power supplies the size of a keychain or lipstick tube (the trend of the moment for smaller chargers) can fully charge a drained smartphone once or twice over. On the other end of the spectrum are powerful chargers rated at more than 25,000 mAh that can juice up to four devices at once, are about the size of a juice box, and weigh just about a pound.
It can take anywhere between a few hours to overnight to completely recharge a mobile device using a portable charger, but bigger, higher-capacity portable chargers can power up devices faster than their mini counterparts. The charger itself also needs to be charged. Some have pass-through charging, so the charger can re-juice your devices while it recharges itself -- a real convenience, when you're pressed for time and outlets.
Reliability can be an issue. Looking through user reviews, tales of poor quality products or cheap knockoffs of better regarded external battery packs are easy to find. Because there are hundreds of portable USB chargers to choose from, it's generally advisable to stick with models from better regarded names, such as Anker, Jackery, Zendure, LimeFuel, New Trent and others. Portable power supplies from these and other makers are backed by a warranty, have a reasonable life expectancy, and have important features such as protection against overcharging, so they won't damage or overheat your devices.
Having an external battery pack with enough reserve power to charge your devices can be very handy, especially during emergencies. The best portable chargers are powerful enough to charge devices like smartphones, tablets and music players (such as the Apple iPod) nearly as quickly as a wall charger. The best models are also long lived -- able to be recharged and discharged for hundreds of cycles before their own internal batteries give out. Most can be recharged from a powered USB port on a computer or laptop, but fastest recharging is almost invariably via a wall outlet power supply -- most likely the one that came with your mobile device since most portable chargers don't include one in the box.
For this edition of this report, the Zendure 2nd Gen A2 (Est. $30) is an easy Best Reviewed choice. "The Zendure A2 changes everything," says Marie Brewis at PC Advisor. There's always a "catch" with portable chargers, but the Zendure truly has it all -- It's pocketable, powerful, fast-charging, inexpensive and stylish (its brushed-silver body looks like a tiny Samsonite gun case). Oh, and it's "the most durable portable charger in the world," GadgetViper.com adds, posting a video of it and other Zendure chargers being run over by a car to back that up.
The speedy Zendure A2 aces tough tests at TheWirecutter.com. It can charge itself in 4 hours, and it holds enough juice (6,700 mAh) to charge your smartphone twice. Still, this is the baby brother of the Zendure family; Zendure's slightly bigger, more powerful models can charge more devices at once (the Zendure A2 has just one USB jack). Versions of the A2 with and without pass-through charging are available.
However, experts still like the little Zendure A2 best. It's about the size of a business card, 1 inch thick, and just 5 ounces -- very convenient. "[The] A2 hits the sweet spot between price, capacity and portability," says PC Advisor, naming it "the best power bank."
Also consider the Aukey PB-T1 (Est. $30), especially if your smartphone or tablet boasts Quick Charge 2.0 (such as the Samsung Galaxy Note). Quick Charge 2.0 promises to cut charging time by up to 75 percent -- and the Aukey PB-T1 is one of the few portable chargers that's compatible with that. "[Thirty] minutes on this charger will give owners nearly 50% battery life," says Cory Gunther at GottaBeMobile.com, naming it one of the 12 best portable chargers. "Enough for the rest of an evening, or to get you through a busy work day."
The Aukey PB-T1 can also charge non-Quick Charge devices, automatically detecting them and using a slower charging rate. One negative: though it has a higher capacity at 10,000-mAh, the PB-T1 charger is roughly twice the size of the Zendure A2 and more than twice as heavy (at nearly 13 ounces) -- so you'll probably want to carry it in your bag, not your pocket.
Mini portable chargers are external battery packs that can easily slip into a pocket or hang on a keychain. These chargers don't have high-capacity batteries (most range from 1,000 mAh to 3,000 mAh) but they're ideal for putting a charge onto a cellphone or even a smartphone or tablet (though perhaps not to full capacity)
The lipstick-sized Anker 2nd Gen Astro Mini (Est. $22) "is an Amazon bestseller for good reason," says Marie Brewis at PC Advisor. Unlike a lot of cheap, unreliable lipstick chargers you can pick up at the checkout counter, this one's the real deal. It sports a rugged anodized aluminum case and more efficient 3,200 mAh power cells than most minis, so it'll actually charge your smartphone fully.
Unlike most cheap lipstick chargers, the Astro Mini is brainy enough to sense your device's recharge rate and match it automatically -- "an undeniably cool feature that meant the Anker was able to charge even our iPad mini, and iPads are notorious for being fussy about the devices from which they charge," Brewis says.
Amazon.com customers overwhelmingly love the Anker 2nd Gen Astro Mini. With more than 17,000 reviews, it earns 4.4 out of 5 stars. Owners say the Astro Mini can take a while to charge itself (4 to 6 hours), but it charges phones quickly. The tiny Mini is especially handy if you need to keep using your phone while it charges, because it just slips into your pocket. It's available in black, silver, gold, pink and blue.
The Astro Mini earns a spot on GottaBeMobile.com's list of the 12 best portable chargers. Reviewer Cory Gunther sums it up: "If you want [a] cheap and portable battery, get this."
High-capacity portable chargers are ideal for travelers who constantly use several personal electronics devices, but are not always near an outlet. These mega-chargers certainly aren't the smallest of the bunch, but they pack the power needed to charge smartphones, music players, tablets and more, even simultaneously.
The Best Reviewed choice in this category is the Zendure 2nd Gen A8 Pro (Est. $70). It looks just like a bigger version of the pocket-sized Zendure 2nd Gen A2 (Est. $30) -- but with nearly four times the capacity (a mammoth 25,600 mAh), four USB ports (so you can charge four gadgets at once) and pass-through charging (so you can charge the A8 Pro while it charges your devices). It also adds an LED display that shows exactly what percentage of the A8 Pro's power remains.
And for such a powerful charger, it's pretty small, experts say. It's about the size of a juice box, and it weighs about a pound. "You might not want to slip it into a pocket, but throwing it in a handbag or rucksack is no problem," says Marie Brewis at PC Advisor.
Like the top-rated Zendure 2nd Gen A2, the A8 Pro's stylish brushed-silver case is tough enough to get run over by a car and keep on ticking. And it's powerful enough to charge an iPhone eight to 10 times -- plenty for even long camping trips, vacations, and hugely important conferences.
"The Zendure A8 Pro is an absolute beast, it's the Incredible Hulk of external batteries," says Simon Tunnard at GadgetViper.com "When it comes to high capacity power banks the Zendure A8 Pro is in a league of its own and worth every penny."
Perhaps because there are so many portable chargers on the market, there aren't as many professional reviews from highly reputable tech sites as one would expect -- although tests at TheWirecutter.com and PC Advisor are outstanding. Other sites, such as GottaBeMobile.com and GadgetViper.com, offer valuable insight and critical reviews, too. User reviews -- and there are thousands of them at sites like Amazon.com and BestBuy.com -- add to the picture as well, including feedback on issues like reliability and support that expert reviewers often can't address. After analyzing all of this data, we've found the best portable chargers based on design and performance.