Anker's 2nd Gen Astro3 is the successor to its wildly popular Astro3E. It boasts more power (12,000 mAh as opposed to the 3E's 10,000) and powers up to three devices at once.
Smart port; smart design. Anker's 2nd Gen Astro3 offers a wallop of power (12,000 mAh battery) in a small package. Astro3 isn't the lightest, smallest or trendiest on the market -- it comes in black or white, weighs less than a pound and is about the size of a dense smartphone -- but reviewers rave about its triple-port design, including a smart port that can identify your devices and ensures they're charging at full speed. (For example, Apple and Android devices tend to require different levels of power.) Three devices can be charged at once. The battery includes a 10-point LED indicator, which gives more detail on the battery's status than competitors' indicators that use colors or fewer lights. Instead of an on/off button, the Astro3 can be shaken awake. It also includes a micro USB cable.
Charges tablets and phones, with room to spare. The Anker Astro3 is powerful enough to charge multiple devices at once. All three of its ports are compatible with a plethora of Apple and Android devices. PhoneArena.com reports that the Astro3 gave six full charges to an iPhone 5s and four charges to other smartphones in its tests. One Amazon.com user found it could fully charge an iPad 2 and still have some power left; a travel blogger reports it could simultaneously charge an iPad, Android tablet and iPhone. Gizmag.com notes that the maximum charge on the universal ports (1.5 Amp) is designed for Androids, so iPhone users seeking the fastest charge should use the smart port. The Astro3 can't be used while it's being recharged, however, and its battery takes about 10 hours to fill up.
Over 800 users give the Astro3 an overall score of 4.7 out of 5 stars. The reviews contain some detailed descriptions and analysis of the external battery charger. Many are more thorough than professional reviews or blogs, which tend to be fairly short and don't test portable USB chargers. Some reviewers note that Anker sent them test products and encouraged them to write reviews.
Review: Anker 2nd Gen Astro3, Contributors to Amazon.com, As of April 2014
This professional review from Tuaw.com (The Unofficial Apple Weblog) tests the Astro3 and praises its design and functionality, noting it worked well with the iPad 3. The reviewer also likes the Astro3's circular LED power meter, which shows how much juice is left.
Review: Anker Astro 3 12,000 mAh, Steven Sande, Sept. 4, 2013
PhoneArena.com praises the Anker Astro3's power, design and other features. The reviewer tests the Astro3 and finds it produces almost six charges for an iPhone 5s and four charges for smartphones with higher-capacity batteries. The website gives the Astro3 a score of 8.5 out of 10, knocking the charger for being "big and bulky."
Review: Anker Astro3 Review, "John V.", Feb. 3, 2014
4. The Travel Insider
This blog review is the longest and the only comparative review of the Anker Astro3. The portable charger shines in tests (including a simultaneous charge of an iPad, Android tablet and iPhone). It takes 10 hours to recharge the Astro3, but the battery's standby storage is "excellent." The Anker is stronger than the Callpod Duo and the Satechi 10,000 mAh, according to David Rowell.
Review: Anker Astro3 12,000 mAh External Battery, David Rowell, Sept. 19, 2013
9To5Mac.com provides one of the more detailed test reviews; the Astro3 charges the reviewer's iPhone 5s (empty to full) six times before dying and takes 8 to 10 hours to charge. (The iPhone plug doesn't charge the device, however.) The Astro3 is deemed "a must-buy for those who need extra energy for their devices wherever they go."
Review: Powering Your Mobile Devices, Scott Buscemi, Oct. 5, 2013
This review describes the Astro3 in detail, but does not appear to formally test the device. The charger still gets a good write-up, including props for its LED status indicator, simultaneous charging and high capacity.
Review: Full Speed Ahead with the Shake-to-Wake Astro3 Portable Battery Pack, Paul Ridden, July 30, 2013
Forbes.com's reviewer recommends the Astro3 as "a good all-around USB battery pack." The Astro3 performs well in tests with the iPhone 4S, the Samsung Galaxy Tab 10.1 and the HTC One, but the write-up for the Astro3 and other battery packs is short.
Review: Great USB Battery Packs, Geoffrey Morrison, Aug. 5, 2013
Lifehacker.com puts Anker's Astro series at the top of its list of best external battery packs, based on reader votes. Although the Astro3 isn't mentioned -- it wasn't released when the list was published -- its predecessor, the 3E, makes the cut along with the entire Astro series because of their high mAh and ability to charge multiple devices at once.
Review: Five Best External Battery Packs, Alan Henry, May 26, 2013
9. iPhoneLife Magazine
This is another positive review for the Astro3, which gets 4 out of 5 stars. The power and ability to charge multiple devices is a pro, but Mike Riley worries that the shake-to-wake feature could drain the battery if it's accidentally jostled. Riley also prefers a numerical LED readout rather than the 10-point light reader.
Review: Does Anker's Astro3 Multi-Device External Battery Deliver?, Mike Riley, Sept. 5, 2013