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625 of 654 people found the following review helpful
This battery pack is beautifully packaged with a black rubberized coated case. The black rubber coating is slightly textured so it is not a fingerprint magnet and it improves the looks of the case and your grip. It is a powerful battery pack rated at 6000 mAh of capacity and the test results were spectacular! I put together a video of the unit and the test results for your review.

The battery weighs in at 4 3/4 ounces. The battery pack has one USB output port that outputs 5 VDC at 2 Amps. It is a smart USB port whose output current will never exceed the capacity of your smart device's current charging capability. The battery is extremely energy efficient and its performance is 10 percent or more above the standard performance of a normal designed external battery. This is because of the superior quality of the battery cells used and the advanced control circuitry within the battery.

During the testing the temperature of the battery pack never even exceeded ambient room temperature. To start your device charging you connect it with the proper cable and the battery pack charging starts automatically. To check the battery pack charge status you have to shake the battery and the LED ring lights up.

This product is outstanding and I rate it at 5 stars. If you are a business person or a student and have to depend on your tablet or smart phone for long periods of time without the ability to get to an AC power source then this is a good battery to own. This is good for those who travel a lot or camp out. Now you can watch your movies or listen to your music on those long airline flights. While this battery pack can put some charge into your tablets it is more ideal for use in recharging your smart phone. Because of its size it is great to drop into a purse, briefcase or a pocket.

You should note that I did not operate my tablets or phones while I charged it but the WIFI and phone transmitter were left on. When I test a battery I do an extensive set of tests that fully charges the battery and then I use it to charge devices and make sure that it is fully depleted when my tests are done. I time each test and document the results as the test progresses. I then calculate the mAh of capacity that the battery supplied and I then calculate its charging efficiency. This process takes from 3 hours to, in very large batteries, about a day for testing. I don't take any short cuts or guess and every battery has these tests performed on it and documented. This is to assure that the battery is tested and it performs well. If a battery has performed poorly I then run the tests again to verify the results.

Items in the box:

* The Anker 2nd Gen Astro 6000 mAh battery
* The battery pack comes with an instruction manual.
* A USB charging cable that is 12 inches long.
* A nice carrying bag for the battery
* You may have to use the charging cable that comes with many of your own devices.

Anker 2nd Gen Astro 6000 mAh External Battery Pack Features:

* Powerful 6000 mAh capacity
* The unit is compact and weighs in at 4 3/4 ounces.
* Attractive design with a black rubberized external coating. The black rubberized coating is slightly textured so it is not a fingerprint magnet and easy to grip.
* The specifications and ports are nicely labeled on the case.
* It has 10 LED status lights in a ring located on the front that indicates the battery charge level. You have to shake the battery and the LED ring will light up and indicate the battery charge level. Each LED represents 10% of capacity.
* This is an ideal size and power of battery to carry in a purse, briefcase or backpack for your smart phone!
* There is one USB power output. It is a USB port rated at 5 VDC and 2 Amps and it is a smart USB port the uses only the current required by your device to properly charge it as quickly as possible.
* When you plug in a device then the charging process of your device begins automatically.
* The battery pack uses Lithium battery technology.
* The battery pack can be recharged 500+ times
* Warranty is 18 months
* The battery pack does not come with an AC wall charger. It is specified to be charged with 5 VDC at 1 amp. It will charge in 5 to 6 hours at 1 Amp input. You can charge the battery using a USB 2.0 port of your computer that is rated at 500 mA but the charging time will be 11 to 12 hours.
* The battery is extremely energy efficient and its performance is 10 percent or more above the standard performance of a normal designed external battery. This is because of the superior quality of the battery cells used and the advanced control circuitry within the battery.

Test charging devices to measure the output capacity:

I charged the battery pack fully before I started my test. I started with a Kindle Fire at 25% and the Anker 2nd Gen Astro was fully charged with 10 LEDs.
* 30 min Kindle Fire at 48% and the Anker battery had 6 LEDs
* 60 min Kindle Fire at 70% and the Anker battery had 4 LEDs
* 90 min Kindle Fire at 82% and the Anker battery had 4 LEDs
* 120 min Kindle Fire at 87% and the Anker battery had 4 LEDs
* 150 min Kindle Fire at 100% and the Anker battery had 4 LEDs

I started with an iPhone 5S at 22% and the Anker 2nd Gen Astro at 4 LEDs.
* 30 min iPhone 5S at 54% and the Anker battery had 3 LEDs
* 60 min iPhone 5S at 84% and the Anker battery had 2 LEDs
* 90 min iPhone 5S at 95% and the Anker battery had 2 LEDs
* 120 min iPhone 5S at 100% and the Anker battery had 2 LEDs

A second iPhone 5S at 79% and the Anker 2nd Gen Astro at 2 LEDs.
* 30 min iPhone 5S at 97% and the Anker battery had 1 LED
* 60 min iPhone 5S at 100% and the Anker battery had 1 LED flashing

I started charging an iPad 2 at 10% and the Anker 2nd Gen Astro at 1 LED flashing.
* In two minutes the iPad was at 12 % and the Anker battery was dead

Summary of charging tests:

* Charge an Kindle Fire 75% x 4400 = 3300 mAh
* Charge an iPhone 5S 78% x 1560 = 1216.8 mAh
* Charge a second iPhone 5S 21% x 1560 = 327.6 mAh
* Charge and iPad 2 2% x 6944 = 139 mAh

* Test result = 3300 + 1216.8 +327.6 + 139 =4983.4 mAh/6000 mAh = 83% efficiency

* That is an outstanding efficiency result for this battery.

Here are some common devices and the amount of mAh of capacity they have when they are fully charged. This is just to give you an impression of how much energy it takes to charge your smart device:

* iPhone 4 battery 1,420 mAh battery capacity
* iPhone 4S battery 1,432 mAh battery capacity
* iPhone 5 battery 1440 mAh battery capacity
* iPhone 5S battery 1560 mAh battery capacity
* iPad 2 battery 6,944 mAh battery capacity
* iPad 3 battery 11,560 mAh battery capacity
* Kindle Fire battery 4400 mAh capacity
* Kindle Keyboard battery 1750 mAh capacity
* iPad 4 battery is 11,486 mAh 3.7 VDC at 42.5 Wh
* iPad Mini battery is 4490 mAh at 3.72 VDC 16.7 Wh

As you can see the Anker 2nd Gen Astro 6000 will not fully charge a totally dead iPad 2, 3 or 4 because it only contains 6000 mAh of capacity. You have to consider the losses in the charging circuits of both the battery pack and the device you are charging. When using an external battery you have to allow approximately 30 % of the battery capacity will be lost to heat, voltage conversion, powering the batteries electronics and the electronics of your electronics device's charging circuits. In addition you have to consider that your device is not truly off like a cell phone is still connected to the WIFI and phone networks and probably receiving emails, etc.

Real world examples of charging capability with this battery pack:

* iPhone 4 approximately 351% of a full charge out of a fully charged Anker 2nd Gen Astro 6000 mAh battery pack
* iPhone 5S approximately 319.5% of a full charge
* iPad 2 approximately 71.8% of a full charge
* iPad 3 or 4 approximately 43% of a full charge
* iPad Mini approximately 111% of a full charge
* Kindle Fire approximately 113% of a full charge

* A normal estimated usable storage is 70% of capacity or .70 * 6000 mAh = 4200 mAh charging capacity available for your electronic devices.

* In my testing I was able to use approximately 4983.4 mAh of capacity or roughly 83% of the 6000 mAh capacity. This is an outstanding result.

I received a sample product for evaluation and I promised to provide a fair and honest review.
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151 of 168 people found the following review helpful
TOP 500 REVIEWERon October 17, 2013
After rolling out new 2nd generation versions of Astro 3 (3 outputs) and Astro 2 (2 outputs), now is a turn for Astro with a single charging output. While Astro 3 was very impressive with three outputs and 12000 mAh capacity, it was a relatively large and heavy device, which is expected. Astro 2 shrunk it down to 2 outputs and 9000 mAh capacity with a more pocket friendly footprint. Here with single output Astro and 6000 mAh capacity the size was reduced down to an awesome compact size which you can store even inside of a very small purse. But don't let the small size fool you - you still get all new 2nd gen design with every bell'n'whistle of Astro 2 and 3. So let's take a closer look.

Continuing with their environmentally friendly packaging, battery came inside of a neatly packaged box which contained a battery itself, a manual (always very detailed), and accessory box with usb to micro-usb cable and a mesh draw-string storage bag for a battery and a cable. Now let me tell you about the size of this battery - its is SMALL!!! Weighting around 130g and with a size of 90mm by 45mm and thickness of 25mm - it will easily fit in a palm of your hand where you can make a fist hiding it inside. That's how compact it is. With a new rounded design and smooth edges, the hard plastic shell is lined with a soft touch rubbery finish. You get one micro-usb battery charging port (1A speed to charge the battery itself) and one full usb smart output port for any Android or Apple device. The output supports a maximum charging speed of up to 2A. In my quick test with OEM usb cable I confirmed a charging speed of 1.5A using my Note 2. The speed will obviously vary depending on the cable you use, so keep that in mind and use usb cables with thicker wires.

Just like with Astro 2 and 3, this 2nd gen device uses a new 10-segment circle LED indicator to show you the charging progress of the battery or the remaining charge on the battery in increments of 10% thus giving you a higher precision reading. Most of the other batteries usually include 4 LEDs to indicate 25% increments, but with Astro you are getting a better precision. There is no power button anywhere around smooth surface of this battery. To start the charging or to check the remaining capacity you just shake it and display LED comes alive. Also, considering actual capacity of any external battery is typically 30% less then advertised value, in case of 2nd gen Astro a more efficient conversion circuit is used which gives close to 80% efficiency, so you can count on about 4700-4800 mAh of charging power. Considering super compact shape of this battery, this is very impressive and perfect as a portable emergency charge you can take with you anywhere.

Overall, the design, the efficiency, the charging speed, and compact size of this battery makes it a very attractive package. It is also very unique and sets it apart from competition. Add to that Anker's 18-month warranty and great support - with introductory price of $29.99 on Amazon this is one fantastic value. I highly recommend it!
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60 of 72 people found the following review helpful
on November 7, 2013
This batter pack worked great for a few weeks. Then one day it wouldn't charge again, and the light doesn't come on.
I have used other Anker products in the past and they have been great. Not sure what's up with this one.
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30 of 36 people found the following review helpful
on June 13, 2014
This battery just didn't work properly. I got the green one in February of this year, and about a month later it was already malfunctioning. It wouldn't "wake up" when I shook it to power on. It had a full or almost full charge, which I know because it would "wake up" when I plugged it into a power source (wall socket) and the little circle indicator would light up to let me know how much of a charge the battery held. The problem was that when it was away from being charged and taken on the road when I was using it for its intended purposes, it would just not wake up. I contacted customer support and they were responsive, which is good, and sent me a new one.

Well a month later after this one arrived, the same issue happens! The battery has a charge, it shows it does- but as soon as it's taken off the charger (wall socket via iPhone AC adapter and charge cord it comes with) it is completely unresponsive. I told customer support and they issued me a refund since this was within their warranty period of a year. (I think Amazon claimed 18 months but Anker says 12, btw.) Anyway they said they would notify the warehouse manager and test out their remaining batteries to see if it was a quality control issue. I think it obviously is, and it was a bummer (multiple times) to be on the road traveling, expecting to use your external battery to save your dying smartphone, only to find it's just a dead clunky box of uselessness. This thing has some weight to it too (as expected) so it was mildly infuriating to have this happen repeatedly after having carried it around in my already-too-full purse all day while traveling.

Edit 8/2014: I had customer service contact me to try to resolve the issue. I have to say they seem to be committed to having me be as satisfied as I could be at this point. They were communicative and responsive, so I would say I am at least happy with their customer service.
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30 of 36 people found the following review helpful
on February 18, 2015
Wow. I'm SO glad I paid nearly $30 for a USED and BROKEN product from Anker through Amazon.

I was so excited yesterday when I was notified that my package from Amazon was delivered! I got home, grabbed the box and opened it, as excited as a kid on Christmas morning. I slowly and carefully took my Anker 6400mAh Power Bank out of it's packaging. First thoughts: wow! This thing is small and pretty lightweight- perfect for my purse! I grabbed the information booklet and read it, learning about the power bank. I then plugged it in to charge.

I waited for the light to come on signaling it was charging. Nothing. Hm. Tried a different outlet. Nada. Hm. Well, I'll let it power for an hour or two and then check on it. After dinner I checked on it only to be disappointed again.

I unplugged it and started carefully inspecting the product. Whoa! This thing looks like it barely survived a war! Both ends are scratched and dingy. The Micro USB port is crooked. There are two cracks in the plastic on the charging end. It rattles when I lightly shake it, almost as if a piece is loose inside the power bank. Upon further investigation, I saw the specs: 6000mAh. It CLEARLY states 6400mAh online. Well that's just a blatant lie.

I've owned Anker products in the past ordered off Amazon and I've never had a problem. I also don't generally write reviews, but this is an exception.
Waste of time.
Waste of money.

I will be exchanging this for a different brand power bank ASAP.
I am EXTREMELY disappointed in both Anker and Amazon for this.
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16 of 19 people found the following review helpful
on February 25, 2014
I really liked the look, feel, and build. The only problem is that it didn't work every time. It sometimes just refuses to charge my iphone 5 although the indicator shows that its fully charged.
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13 of 15 people found the following review helpful
on July 4, 2014
This is the second external battery i bought from anker and it really sucks that after about 10 uses it does not charge and it does not light up anything really disappointed will be sending it back soon hopes this helps.
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29 of 37 people found the following review helpful
on November 16, 2013
Item failed on first use - charged Iphone from 8% to 16%, then started backing down to 13% - even while still showing it had enough power to perform a change

Contacted Anker support through their website and received no response at all. Sent them a detailed email with Amazon receipt number, model number, and description of problem days ago - nothing came back - really very shocked.

Have used and been happy with other Anker products in the past, but this is just garbage and their lack of response to my email just makes it even worse.

Very disappointed in both the product and the company

---------

Update - Anker followed up with me after seeing my review here. They sent me another unit, which did work. The product now charges my Iphone 5, but it does charge it rather slowly.

I do appreciate their customer service following up and coming to the rescue, however

That said, I also have one of their 5 in 1 (Anker® 25W 5-Port USB Wall Charger) wall chargers that I purchased a week ago - this worked for a few days and then died

Based on my experiences with these two items, I have to conclude that Anker is having some quality control issues at this time - which is really a shame for a company that makes such well thought out products.

I am hopeful that they can get their issues worked out and will update as further developments happen
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12 of 14 people found the following review helpful
on May 28, 2014
I liked the size and power capacity this one had.

But unfortunately you will be lucky if you get a working piece!

I ordered 3 of these at once, so far opened 2 of them and only one is still working but the second one stopped working after a few weeks!!!!

It just stopped working, does not get charged nor charge no matter what I do!!

That's a shame for a premium device with premium price, I wanted to run away from the chinese generics but whats the use!!

I really want a brand to trust, they should reimburse the customer directly for such inconvenience and money paid!

That's really unprofessional.
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6 of 6 people found the following review helpful
on March 13, 2014
It's a great product if you're out and about without a charging place in sight. It's heavier than my phone (S4) though, but does it's job well. It's able to charge my phone proficiently, as long as i'm not using my phone while it's charging it.

Only real cons I have about this product is that it takes too long to charge itself and it scratches easily. So the black bag they give is not really a commodity more of a requirement to prevent scratches (Uploaded pictures).

It's such a great product though I bought another one.

Update: It's been 3 months and both have broken down. I'm not sure if I just simply used all the battery, but they won't recharge themselves. I was able to get a refund directly from Anker though as they sent me a follow up email.
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