Bought two of these. Anker is pretty good quality. What we found with this model is that is DOES hold a large electricity supply, but it has very poor shelf life. That is, if I fully charge it, then keep it on my desk for a week or two without using it, it DISCHARGES completely. While in use, yes, it can power a phone or two quite well. But it is not reliable as a backup if it has been sitting around more that a few days.
EDIT:
Dec. 9, 2016: The seller noticed my poor review and felt that they wanted to help me out. They sent me another battery FREE, postage prepaid. It works perfectly-- good shelf life, not like the first two. When I told the seller, then they sent me ANOTHER one... free. So now I have two GOOD ones which do hold the shelf life, from a company who really cares about making the product right!

This battery pack is ideal for your purse, pocket or backpack and it is one of the most portable batteries that I have tested. It had good test results. This is an exceptional charger with a feature that everyone needs. The feature is PowerIQ charging technology for the charging port on this battery charger. That means that you can plug in any type of device and this smart port will set the charging current to match the maximum charging rate that your device can safely handle. The port is rated at 5 VDC and up to 2 Amps but in my testing I was able to charge and Apple iPad Air at 2.1 amps.

Many people don't realize that device manufacturers play games by wiring their devices and cables differently so that a charger that is designed to charge an Android device will not quickly charge an Apple device. Manufacturers like Apple, Samsung, Android devices and Chinese smart devices have different circuitry in them and if the charger doesn't match their circuitry they can charge at a much slower rate. The IQ port doesn't care what type of device you plug into it because it adapts its charging rate to match what the device wants by sensing what type of device is plugged into it. I was so impressed that I put together a video of the unit and the test results for your review.

The construction of this battery pack is simply beautiful. The exterior shell is glossy black. The battery weighs in at 4.23 ounces. The battery pack has one smart IQ output port that output 5 VDC at variable current to meet the charging requirements of the device you have plugged into it. It is called a Smart Port or an IQ port. It uses a chip to help select the proper current to allow the maximum safe charging current for the fastest device charging. The port can output as much as 2 amps but the battery pack in my testing output up to 2.1 Amps while charging an Apple iPad Air.

This battery pack has enough power to charge an iPhone 5S 217%. To start your devices charging connect them with the proper cable. (You will probably have to use your own charging cable that came with your device) and charging starts after you press the on button on the side of the battery. The charging will stop automatically when your device is fully charged or the battery pack is depleted.

The battery pack has 4 blue LEDs on it and when it is charging they work like this:

* One LED blinking = less than 25%
* One LED on and one blinking = 25 to 50%
* Two LEDs on and one blinking = 50 to 75%
* Three LEDs on and one blinking = 75 to 99%
* Four LEDs on and the battery pack is fully charged

The Lithium battery can be recharged over 500 times during its life cycle. It comes with an 18 month warranty. It is recommended to charge the battery at 1 Amp and 5 VDC. It will take 5 hours to charge the battery at that charging rate. You can use your USB 2.0 port of your computer it takes 10 hours at ½ Amp input. You can even use an AC powered USB wall charger or a USB car charger and using up to 2 amps will not hurt the battery.

The battery pack does have a power on switch to turn on the charging cycle for your device or to allow you to check the battery's remaining power charge. .

Items in the box:

* The battery itself
* An USB to Micro USB charging cable that is 27 inches long

Anker 5200 mAh second generation battery pack test data:

iPhone 5S unit one 74% - battery fully charged with 4 LEDs

* 30 minutes 96% - battery 4 LEDs
* 50 minutes 100% - battery 4 LEDs

* 26% x 1560 mAh = 405.6 mAh

iPhone 5S unit two 32% - battery 4 LEDs remaining

* 30 minutes 63% - battery 3 LEDs
* 60 minutes 91% - battery 3 LEDs
* 90 minutes 100% - battery 3 LEDs

* 68% x 1560 mAh = 1060.5mAh

Samsung Galaxy Tab 4 at 54% - battery 3 LEDs remaining

* 30 minutes 66% battery 2 LEDs
* 60 minutes 77% battery 2 LEDs
* 90 minutes 89% battery 1 LED
* 120 minutes 97% battery dead

* 43% x 4450 mAh = 1913.5 mAh

Summary of all items charged:

* 405.6 mAh + 1060.8 mAh + 1913.5 mAh = 3379.9 mAh / 5200 mAh = 65% efficiency

* This is a good result and gives this battery a 5 star rating especially after charging a larger tablet in the testing.

Device internal battery requirements:

* 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
* iPad Air battery is 8820 mAh capacity
* iPad Air 2 battery is 7340 mAh capacity
* Samsung Galaxy Tab 4 - 8 inch Tablet 4,450 mAh

As you can see the Anker 5200 mAh will not fully charge a totally dead iPad 3 or 4 because it contains only 5200 mAh of capacity. That battery is ideal for recharging your smart phone or smaller smart tablet.

You have to consider the losses in the charging circuits of both the battery pack and the device you are charging so this result is outstanding! 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. This is one of the most powerful rechargeable battery packs I have tested.

Real world examples of charging capability with this battery pack:

* iPhone 4 approximately 238% of a full charge out of a fully charged Anker 20000 mAh battery pack
* iPhone 5S approximately 217% of a full charge
* iPad 2 approximately 49% of a full charge
* iPad 3 or 4 approximately 29% of a full charge
* iPad Mini approximately 75.3% of a full charge
* Kindle Fire approximately 76.8% of a full charge
* iPad Air approximately 38% of a full charge
* iPad Air 2 approximately 46% pf a full charge
* Samsung Tab 4 eight inch tablet approximately 76% of a full charge

* A normal estimated usable storage is 70% of capacity or .70 * 5200 mAh = 3640 mAh charging capacity available for your electronic devices.

* In my testing I was able to use approximately 3379.9 mAh of capacity or roughly 65% of the 5200 mAh capacity. This is a good result for a battery of this size. This was based upon the first full charge of the battery pack and the results should get better after the battery is charged several more times.

I was supplied a sample for test and evaluation. A review was not promised to the supplier in exchange for the sample but I stated that if I provided a review that it would be fair and honest.

No wonder this is the top rated portable power bank. I've had this thing for a few months now and wow am I impressed. The charge that this power bank holds is incredible given its size! I use an iPhone SE and I've gotten 2 full charges out of this with extra battery to spare! It's obvious that the folks at Anker really care about giving you a quality product at an unbeatable price. The prices of these things elsewhere are insane. Before purchasing this I looked at Walmart and the ones they had at this price looked horrible. The charge cord was very sturdy and the carrying bag fits the charger and cord perfectly. I also love that it has a battery level indicator. I carry this with my every single day. Would recommend for literally everyone. There's not a smartphone user on this earth that wouldn't benefit from having one of these.

Hi,

This is my review of the Anker Astro E1 5200mAh External Battery. I have evaluated it for a few days to provide my personal review and user experience. For my test, I have used an iPhone 5s and iPad Air.

First Impressions:

This product arrived in a plastic cover wrap that protected the exterior boxing and cover which I appreciated.

Upon first look, there’s the top side which shows the Astro E1 picture. The front side provides a customer service phone number and e-mail to contact Anker if product support or returns are needed. The backside has the serial number for the product. The bottom side has the IQ technology brief summary to learn more about it.

In order to view the Welcome Guide, you have to tear to open the front side to reveal it on the opposite side of the cover. I didn’t personally like this idea because once you tear part of the cover up, it sort of dangles around in which makes it hard to put away. It would’ve been better to have the traditional method of including a small pocket sized Welcome Guide inside the box.

Inside contains the following information:

- 4 LED dots lit on the Astro E1 represent 100% charged capacity, 2 dots is 50% charged capacity, and 1 dot is 25% charged capacity.

- Anker provides a 30 day money back policy and 18 month warranty, which is something that I’m happy about. Most competitive electronic companies these days offer 18 month warranty, so I am glad to see Anker provides that as well. That gives ample time to evaluate the Astro E1 through many recharging cycles to evaluate for defects.

The cardboard construction of the box is sturdy and useful for shipment and travel purposes. First thing I notice when opening up the box is the Astro E1 in a plastic sleeve. The Astro E1, to my surprise, very small. Nearly smaller than any other External Battery that I have ever evaluated to this date in time.

Putting that aside is another layer of cardboard enclosure which has a marketing material advertisement on the Power IQ technology. Power IQ technology allows devices plugged into the External Battery to have the fastest charge possible and will automatically adjust to different input current sources.

Underneath that is the Micro USB cable to charge the Astro E1 that measures about 26 inches across, which is just above 2 feet.

The Astro E1 is small. I measured with my measuring tape roughly 4 x 2 x 0.75 in based on rounding. This is great for portability and fitting into even a pocket in your pants. I have taken some pictures to compare this with a cellular flip phone, iPhone 5s, and my hand attached to this review.

Upon first powering up the Astro E1, I found the charge capacity was at 3 LED lights, which is 75%. I didn’t want to charge it to 100% yet because a rule of thumb is to only charge the External Batteries when 25% or lower for greater lifespan.

Usage:

For my first test, I charged an iPhone 5s that was completely drained of its battery at near 0% to charge with the out of the box Astro E1. Using my lightning cable, I plugged it into the USB port on the Astro E1 labeled IQ and the other end to my iPhone 5s and tested.

Once connected, without even pressing any other buttons, I saw the Astro E1 start to light up the 4 LED lights back and forth until finally settling on the 3 LED lights that indicates its current charge capacity.

The following is observations based on using my Battery Doctor App in the iPhone 5s.

Charge start time: 5:28pm, Astro E1 at 3 LEDs

Checkpoint: 6:27pm, iPhone 5s charging at 59%, Astro E1 at 2 LEDs

Checkpoint: 7:29pm, iPhone 5s charging at 99%, Astro E1 at 2 LEDs

Checkpoint : 8:22pm, iPhone 5s charged 100%, Astro E1 at 2 LEDs

Conclusion: Astro E1 charged iPhone 5s from 0% to 100% from out of the box at 3 LED indicators in about 2 hours and 54 minutes with room to spare for another full iPhone 5s charge.

For my second test, I recharged my iPhone 5s for a second time around when it was at 22% battery life with the remaining charge in the Astro E1 from a few days ago.

Charge start time: 10:11am, Astro E1 at 2 LEDs

Checkpoint: 10:53am, iPhone 5s charged up to 65%, Astro E1 fully depleted with no LEDs displayed

Conclusion #1: It took about 42 minutes to charge up 43% of my iPhone 5s on a quick charge using Battery Doctor App for iOS.

Conclusion #2: With the Astro E1 at 3 LEDs to start, which indicate 75%, I was able to charge one and a half times my iPhone 5s before it fully depleted.

For my third test, I evaluated how long it would take to charge a fully depleted Astro E1 to fully charged. Since the input is 1A, I found that my laptop, which is running throughout the day, would be sufficient to charge this device using one of the available USB 3.0 ports on my PC.

Charge start time: 11:05am, Astro E1 at 1 LED blinking

Checkpoint: 12:13pm, Astro E1 at 2nd LED blinking

Checkpoint: 1:20pm, Astro E1 at 3rd LED blinking

Checkpoint: 3:17pm, Astro E1 at 4th LED blinking

Checkpoint: 7:04pm, Astro E1 turned off, fully charged

Conclusion: Although I had to step out after 3:17pm away from the device while charging, I can estimate that it takes between 4-5 hours to fully charge the Astro E1.

For my fourth and final test, I went ahead and checked to see how much of a boost that the Astro E1 gives when fully charged to increase battery life on my iPad Air tablet.

The following are observations based on using my Battery Doctor App in the iPad Air tablet.

Charge start time: iPad battery 17% at 7:05pm, Astro E1 4 LEDs

Checkpoint: 8:11pm, iPad battery 48% charge, Astro E1 1 LED blinking

Checkpoint: 8:26pm, iPad battery 51% charge, Astro E1 fully depleted

Conclusion: iPad Air gets a 34% battery life increase from a fully charged Astro E1 in 1 hour and 21 minutes

In Summary:

Pros:

1) Small portable size with smooth finish to allow easy access for travel needs
2) Charges smartphones at least two full times
3) Power IQ Technology allows save charging for different specs of USB powered devices
4) Simple LED display to indicate a range in battery life remaining

Cons:

1) 4 LED indicators may sometimes be inaccurate when fully depleted or gradually progressively charging towards full based on my tests

Suggestions:

1) Use a digital display screen to indicate actual charge remaining before depleted or fully charged in the Astro E1 rather than use 4 LED dot indicators to specify 25% intervals of ranges

2) Use a small alarm sound built into the device to indicate when device is fully charged, fully depleted, or when device being charged with the Astro E1 has charged completely to 100% and can be removed or disconnected from the Astro E1.

User Scenarios:

1) This product works great for people who go outside of the house and don’t want to carry anything excessive around as the Astro E1 can fit into your pocket of any type of pants or shorts fairly easily.

2) It works well to put away in the glove compartment of a car for emergency reasons.

3) This works will for those who are stationary at some table for a while for instance, those who are dining or eating out, to have this thing charge on the table your smartphone or tablet while you’re using it.

Overall, I enjoyed evaluating this product. The small size and shape of the Astro E1 will fit in well in the long run for better accessibility and handling.

I was provided a sample to evaluate to provide personal feedback of the user experience to help prospective buyers as well as product management teams to continue learning how to improve the product.

Thanks for reading my review.