Tech review: The best portable USB battery pack for daily use
This post was done in partnership with The Wirecutter, a buyer’s guide to the best technology.
Smartphone batteries don't always last through a busy day, but a pocket-size USB battery pack can give your handset enough of a boost to survive the evening. After 40 hours of research and 65 hours of testing, the one we like the most is Anker's 2nd Gen Astro 6400. It fits in any pocket or purse, and it charges phones and small tablets about as fast as any pocket-friendly pack out there. At 6,400 mAh, a measurement of battery life, it has a larger capacity than most, too.
How we decided
We started by looking for packs that could slide into a relaxed-fit jeans pocket without bulging too much. We also wanted a pack that could fully charge power-hungry phones like the Apple iPhone 6, Motorola Moto X and Samsung Galaxy S6 at least once, and at full speed. From there, we favored packs with the best cost-to-capacity and size-to-capacity ratios and higher-current power output (up to a point).
We settled on eight finalists and put each pack through a timed charging test on a few different devices so that we could measure charging speed. Wirecutter staff also evaluated each battery.
Our pick
Our pick The Anker 2nd Gen Astro 6400 can slide into a relaxed-fit pants pocket alongside a smartphone, though a jacket pocket or purse will be a more comfortable fit.
The Anker 2nd Gen Astro 6400 can slide into a relaxed-fit pants pocket alongside a smartphone, though a jacket pocket or purse will be a more comfortable fit.
The Anker 2nd Gen Astro 6400 ($20) is the best pocket-size USB battery for most people because it comes closest to hitting the sweet spot for price, charging speed, capacity and portability. Thanks to its smart-charging circuitry, it works well with any current smartphone, and it should be able to handle new models that come out in the next couple of years too. It's sturdy enough for the daily grind and small enough for a pair of relaxed-fit jeans.
Runner up, with pass-through charging
Runner-up, with pass-through charging The Zendure A2 is your best bet if you need pass-through charging, but it’s larger and more expensive than our favorite pack, the Astro 2nd Gen Astro 6400.
The Zendure A2 is your best bet if you need pass-through charging, but it is larger and more expensive than our favorite pack, the Anker 2nd Gen Astro 6400.
If you need pass-through charging (the ability to connect the battery pack to both a wall charger and a device), and if you want to have two gadgets charge in sequence (or simultaneously)—the 6,400 mAh Zendure A2 is the best pack we found. It performed just as well as the Anker and AmazonBasics packs, but it's bulkier and more expensive than the Anker.
A flatter pack
More than half of the Wirecutter staff preferred the narrower but thicker shape of the Anker 2nd Gen Astro 6400 (left) to the flatter, wider AmazonBasics pack (right).
More than half of the Wirecutter staff preferred the narrower but thicker shape of the Anker 2nd Gen Astro 6400 (left) to the flatter, wider AmazonBasics pack (right).
If you don't like the chunkier shape of the Anker 2nd Gen Astro 6400, the AmazonBasics Portable External Battery Charger 5600 ($25) might be more your style. It offers the lowest price and the best overall price-to-capacity ratio among our finalists. We didn't name it our top pick because a slim majority of Wirecutter staffers preferred the candy-bar shape of the Anker over the smartphone-like slab shape of the AmazonBasics. The capacity is a bit less than that of other packs, but it's as good a battery pack as the Anker.
A really, really small and portable USB pack
A really, really small and portable USB pack As long as your wallet isn’t overstuffed, the TravelCard can fit into the slots.
As long as your wallet is not overstuffed, the TravelCard can fit into the slots.
Our top picks are small enough to fit into most relaxed-fit pockets, but if you're looking for a very small battery, consider the Go Design TravelCard. It's small enough to fit into most wallets (or slender makeup cases, or tiny clutches, or slim pockets), and it sports a built-in cable (micro-USB or Lightning, depending on the model).
At 1,500 mAh, its capacity is quite a bit smaller than that of our top picks, but it can charge about 50% of the battery in a typical 4.7-inch smartphone. This pack is the "Always have it with me just in case I need a small boost to get through the rest of the day" option.
In closing
For reliable backup battery power that can fit in your pocket, we recommend the Anker 2nd Gen Astro 6400 or the AmazonBasics Portable External Battery Charger 5600—whichever is your preferred shape. If you want something even smaller, the TravelCard is a great alternative.
This guide may have been updated. To see the current recommendation, please go here. The Wirecutter's extensive research and testing is supported by a small commission from the purchases made by its readers.
