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Anker Astro 2 8400mAh External Battery

Anker Astro 2 8400mAh External Battery


Product Description

High Capacity

If you're a long-haul power user, our Anker Astro2 external battery packs deliver 4 full charges or add 33 hours of talk time to your iPhone 4S / 4G / 3GS; 2-3 full charges for Samsung Galaxy S III, or 300% - 400% to most mobile phones' battery life.


Anker Astro2 8400mAh external battery is designed to get you powered up, without getting in the way. You can easily put the Anker Astro2 into your pocket, PERFECT for long plane flights, road trips, or whenever you need to charge your mobile devices wherever you are.


Whether you need to charge your smartphone, iPhone, iPad, PSP, netbook, or tablet, we have the right external battery and matching charging tip for you.


Share the convenience of a portable charge with multiple devices. Simultaneously charge two devices with our Anker Astro2 dual USB external chargers.

Customer Reviews

Simple Solutions
  • Love Anker Products And Great Anker Support!
  • When I first received this product it was defective. I sent a few E-Mails back and forth with Anker support and their techs diagnosed it as "broken". They mailed me a new one and I shipped them the defective one. New product worked as expected and sits in my car for when my friends and I need a recharge mid-evening.
  • 2014-04-15

Hazel L. Lee
  • Great Asset
  • Very good for travel and quick charges. No more roadside flats with dead phone in tow. Highly recommend thus far.
  • 2014-04-15

Steve Govedich
  • Anker Astro 8400mAh Portable Charger
  • This little guy works great. It charges all of my small electronics reliably and it holds its own charge remarkably well.
  • 2014-04-01

  • A great product
  • A friend of mine has one and that is how I learned about anker brand. I am so pleased with the easiness of how it works with both iPhone and iPad. When I'm gone for long periods of time I am confident that I'll have service. I keep the charger with me if I need to charge it. But would recommend that everyone get one.
  • 2014-03-09

Mr Dee
  • Works Perfectly
  • Use this when I am out golfing. Adds the extra juice when I use my phone as a range finder. Phone is constantly on for about 4.5 hours. This power supply has lots of extra reserves for those long rounds too.
  • 2014-02-27
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Customer FAQ

Q1.  Can I use USB cables other than those provided with my Anker external battery?
To ensure complete safety and best performance, we strongly recommend using your device’s original cable, a third-party certified cable (such as MFI) or our included cable.
Q2.  Does it work with the new iPhone 5s, 5c?
Yes. But the Apple connector is not included. Please use your device's original cable.
Q3.  Anker external batteries' efficiency.
ALL external batteries lose power due to voltage conversion and circuit resistance.

Approximately 20% of Astro 2nd Generation external battery’s total capacity is consumed, including power lost from circuit heat and voltage conversion within the external battery (approximately 6%) and the charging cable and your device (approximately 14%). This efficiency rate is 15% higher than the industry average of 35%.

Older Astro batteries have lose approximately 30%.

According to industrial standards, all external batteries are labeled based on their raw cells capacity not efficiency. Like others, we are following this standard.
Q4.  How long will the battery lasts while not in use?
Generally, most of our external batteries' static power consumption is lower than 100uA, which will take between 3.5 and 20 years to drain the battery completely.

However, the chemicals within the li-ion battery will gradually become less active over prolonged periods without use. Most will die in 2 years of inactivity.

To extend your battery's life:
1. Charge and recharge it at least once every 3-4 months.
2. Do not over-charge or over-discharge it. It is best to keep it charged between 5%-95%.
Q5.  Can Anker external batteries be used for international travel?
Yes. Be sure the USB adapter you bring with is compatible with the voltage of the country you will be traveling to. An adapter's voltage input is usually printed on the adapter.
Q6.  Can external batteries be taken on board airplanes?
Yes, all Anker external batteries can legally and safely be taken on board airplanes. Here are the relevant requirements:

Quoted from Federal transportation security rules (Effective January 1, 2008):
Lithium ion batteries (a.k.a.: rechargeable lithium, lithium polymer, LIPO, secondary lithium).
-Passengers may carry consumer-sized lithium ion batteries [no more than 8 grams of equivalent lithium content or 100 watt hours (wh) per battery]. This size covers AA, AAA, 9-volt, cell phone, PDA, camera, camcorder, Gameboy, and standard laptop computer batteries.
-Passengers can also bring two (2) larger lithium ion batteries (more than 8 grams, up to 25 grams of equivalent lithium content per battery) in their carry-on. This size covers larger extended-life laptop batteries. Most consumer lithium ion batteries are below this size.

Anker's largest external battery is currently the Anker Pro 20000mAh (74 wh) which is lower than the above 100 wh limit.
Q7.  What can I do if I lose the provided accessories?
Please check to see if you have extras or contact us via email at for help.
Q8.  Anker external batteries' compatibility
Anker external batteries are compatible with Android and Apple smartphones and tablets except Asus devices (Apple connectors are not included, please use your devices original cable).
Q9.  Can it be charged and charge other devices at the same time?
Q10.  Do I need to press the power button when charging other devices?
Q11.  How long does it take to fully charge this Anker external battery?
7-8 hours with a 1A output charger.
Q12.  How to turnthe flashlight on and off?
Please press the power button for 2 to 6 seconds to turn the flashlight on and off.
Q13.  Can I charge two devices at the same time?
Yes. But please note that when using 2 output ports simultaneously, the total output current will not exceed 3A.
Q14.  What if the Astro2 fails to recharge?
a. Check that the adapter is connected securely, or replace it if the current one is not functioning normally.
b. Check that the USB cable is connected securely, or replace it if the current one is not functioning normally.
c. Please email us at duiring your 18-month warranty period if the provided acessories or the external battery have problems
Q15.  What if the Astro2 fails to charge other devices?
a. Check that the connection between the Astro2 and the electronic device is secure, or replace the cable if the current one is not functioning normally.
b. Check that the Astro2 still holds a charge, and recharge it when the remaining power is low.
c. Check that the Astro2's voltage is compatible with your device's.
d. Please email us at duiring your 18-month warranty period if the provided acessories or the external battery have problems.
Q16.  How can I identify the voltage specification for my device?
Please refer to your device's instruction manual, product labeling, or adapter to find this information.

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Latest Post

Looping CHarger recharge

Hi there, I have a question regarding this product:

Basically, i want to use it to power a small 5v DC input device via a USB to DC barrel plug. However, when I connect an external battery to the device the battery will power down after 30 seconds as if nothing is connected. I have found a work around, by leading the second USB output back into the input of the battery. THis appears to keep the battery on and not time out. However, is this bad for the battery? Can I still do this with out causing major damage to the battery or device I'm powering?


Replies(4) Collapse Report as spam Apr 3, 2014 at 9:08 AM

There's nothing "wrong" with it, but it is very inefficient as you will be losing lots of power to conductivity and heat.

As I read more of Anker's website and product FAQs, I'm finding that they have a position on charging devices while charging the unit. Though it is inconsistent device to device and therefore I'm not certain if it is a physical issue to a technical one.

Not a great answer, but Anker Team needs to chime in for the "official" response. And add that to the FAQ.

Reply Report as spam Apr 3, 2014 at 9:28 AM

Oops, they have...

Yes, this battery can simultaneously charge and discharge. However, constant pass-through charging may affect the battery’s lifespan.



Reply Report as spam Apr 3, 2014 at 9:35 AM
Tech X-Ray

That is still very inefficient, it's not necessarily bad since it's meant to recharge and discharge but it will definitely affect the longevity of the device

Reply Report as spam Apr 5, 2014 at 10:03 PM
Sorry to hear you're having an issue with your Astro2.Could you email us at please and let us know exactly which device it is you're using? Our customer service team will help you out.In terms of the USB routing, we wouldn't recommend you do this as it could shorten the battery's lifespan. You could try plugging a phone into the 2nd USB port, that would keep the battery up and running.
Reply Report as spam Apr 8, 2014 at 5:02 AM
A great piece of energy
Compact to fit in a poket, powerfull to give really much extra time for daily and extra activity. The charging is a bit slow, but you have a whole night to do that
Replies(2) Collapse Report as spam Jan 29, 2014 at 6:09 AM
True, although you may feel it slow at charging but the reason is that its charging your phone via usb. I estimate it charging at 500mAh. Correct me if I'm wrong
Reply Report as spam Jan 29, 2014 at 6:36 PM
Justin Rohr
Charging a big battery like this will take longer than a phone. Just make sure its getting at least 1A for optimal charging time!
Reply Report as spam Jan 29, 2014 at 8:55 PM
need a full package
Hi anker. I got anker 8400 last 2 days. What i get is different from video u attach here. Im only get long wire n extentn for ipad only with anker 8400. I act really need the ext for PSP. What can u do for my situation? Im from malaysia n bought it from dealer from singapore.
Replies(3) Collapse Report as spam Jan 27, 2014 at 10:28 PM
Package only includes: Package includes: Anker® Astro2 External Battery, Micro USB wire, instruction manual, travel pouch. You will need to purchase extra adapters and cables for your device. Try to contact Anker's customer service if they can help you with this: 1-800-988-7973 (US) Mon-Fri 9am-5pm (PST)
Reply Report as spam Jan 27, 2014 at 11:40 PM
What you received is the current package contents. Please contact for further assistance.
Reply Report as spam Feb 13, 2014 at 4:02 AM
IT Owl
Sorry but that is the full package. You can use your old cables to charge as well
Reply Report as spam Jan 28, 2014 at 10:20 AM
is there a reason this will not....
Support a motorola xoom 2?
Replies(6) Collapse Report as spam Jan 8, 2014 at 1:46 PM
xnap that's what i assumed. think i'll just decided when i buy as what one i buy. hopefully they will be really nice and have sales in the next couple of weeks. needed one the other night phone was near dead but had to sit at hospital for 3 hours.
Reply Report as spam Jan 10, 2014 at 6:20 AM
If your motorola xoom 2 can be charged through a computer's USB port, it will work with our astro 2 8400mah.
Reply Report as spam Jan 14, 2014 at 10:40 PM
I believe it will support the Xoom though compatibility as indicated only included the following: Motorola: X Phone, Droid Razr, Bionic / Atrix 2 / Triumph
Reply Report as spam Jan 8, 2014 at 4:58 PM
It will work as the Xoom 2 takes a micro USB port to charge! Anker probably did not list every compatible device as that would be hundred or thousands of devices. And since the Xoom 2 is 3 years old now, it's not a recent device that people carry
Reply Report as spam Jan 8, 2014 at 7:34 PM
thanks guys. i understand that they may no list them all but when i was looking at the astro E4 they said i quote 'This external battery can work with Sony Xperia Go, but isn't compatible with the Motorola Zoom 2. Hope that helps!' i was just wondering why as i understand that a device will only draw what it needs. maybe im wrong but im just trying to understand as im waiting for a deal to appear on amazon. tho i wish amazon send me their god dam free £!0 voucher soon!
Reply Report as spam Jan 9, 2014 at 11:58 AM
Quote From mike551: That's really strange. The 2A can definitely charge your tablet well with no problem. Yep, I'm with you. Hopefully Anker has some sales coming up in January as I'm looking for more external batteries as gifts for family. Can never be without more power as backups. But they're usually good at announcing them on their social networking pages, so follow those to stay tuned
Reply Report as spam Jan 9, 2014 at 6:37 PM
compatibility with samsung galaxy tab 2
Is there a way for this product to work with samsung galaxy tab2 10.1. Is it not supported because the cable is not included in the package? if so can i use a third party cable to charge my tablet or will it still not charge using the proper cable. Thank you in advance Christos Haralambous
Replies(4) Collapse Report as spam Jan 6, 2014 at 5:20 AM
Yes it will work if you use the right cable. Third party cables will also work on it and charge your tablet
Reply Report as spam Jan 6, 2014 at 9:44 AM
As long as you have the right cable, even a third party cable should work. However, be careful of cheap counterfeit cables, as they could damage your device.
Reply Report as spam Jan 6, 2014 at 9:56 AM
Unfortunately, the Astro 8400 is not compatible with the Samsung Galaxy Note 10.1 tablet. Some Samsung tablets require a special charging signal that this battery cannot provide. However, our 2nd Gen Astro batteries will work with the Samsung tablets. Hope that helps!
Reply Report as spam Jan 14, 2014 at 9:58 PM
Nic Smith
I imagine it is just a usb to whatever your phone or tablet uses cable. So, the cable that came with your phone or tablet should be all you need.
Reply Report as spam Jan 9, 2014 at 5:01 PM
charging cable
You could try getting this from Amazon
Replies(3) Collapse Report as spam Oct 13, 2013 at 3:36 AM
Amazon themselves said the cable has problems.
Reply Report as spam Oct 14, 2013 at 4:48 PM
or try these cables: or
Reply Report as spam Oct 14, 2013 at 10:15 PM
Great charging cable recommendation. Thanks for helping out!
Reply Report as spam Oct 17, 2013 at 4:36 AM
Power cord
Hi, I am the happy owner of a anker astro 2 8400 I lost the cable to charge it. Where can I per chase a new one ? (This site, amazon ?) I am in France. Thank you
Replies(2) Collapse Report as spam Oct 12, 2013 at 5:12 PM
I am in the USA. i wen to Frances Amazon and i found this:
Reply Report as spam Oct 13, 2013 at 1:58 PM
Yup, just any Micro USB cable will do. You don't need a specialized one.
Reply Report as spam Oct 16, 2013 at 4:24 AM
Great product
I have two Anker Astro 2 8400mAh and both have worked nicely for changing iPhone & iPad. Got them to use on a camping trip when power was not readily available. Have charged with solar panel between access to AC power. After about 4 months of ownership I would recommend the battery line and would strongly consider other product lines. I would love to be able to obtain a power tip that fits the new Apple products (iPhone 5/5S).
Replies(2) Collapse Report as spam Sep 28, 2013 at 8:23 PM
Glad to hear you like our products! Unfortunately, at this point we are not authorized by Apple to produce connectors compatible with their products - working hard to change that though. In the meantime, we apologize for the inconvenience.
Reply Report as spam Sep 30, 2013 at 4:17 AM
Quote From ANKER Team: You should sell a connector that is certified. I know it is more expensive. Keep up the good work.
Reply Report as spam Oct 13, 2013 at 2:00 PM
Power tip for iPhone 5/5S?
I have two Anker Astro 2 8400mAh. Is it possible to obtain a power tip that fits the newer Apple products. It is cumbersome to carry along an entire power cord where a compatible tip would be better.
Replies(2) Collapse Report as spam Sep 28, 2013 at 8:15 PM
Unfortunately, we don't currently have a connector for them, but are working hard to become certified so we can include Apple connectors in future product releases. In the meantime, sorry about the cumbersome cord...
Reply Report as spam Sep 30, 2013 at 4:06 AM
Maybe a very short Lightning cable will do the trick. Put it in a carrying case and you are good to go.
Reply Report as spam Oct 14, 2013 at 4:50 PM


Hi, could you please tell me if the Anker Astro 2 8400mAh External Battery is compatible with Samsung Galaxy Note 10.1 and Motorola DEFY+. Thanks Gopi
Replies(1) Collapse Report as spam Aug 23, 2013 at 5:29 AM
Unfortunately, the Astro 2 is not compatible with Samsung tablets. You should check out either our Astro Pro line (10000mAh or 14400mAh) or the Astro E4/E5 to power your Samsung tablet. As for your Motorola, any of our Astro batteries will do the trick.
Reply Report as spam Aug 26, 2013 at 2:22 AM
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