Your Position: Home > Power > Portable Chargers > External Batteries > Astro Slim >

Anker Astro Slim2 4500mAh External Battery

Anker Astro Slim2 4500mAh External Battery


Product Description

Our goal was simple: design a powerful battery that stacks up – literally.

Slimmer and stronger.

At (0.39in), Anker's Astro Slim2 comes with enough power for 2-3 charges on most smartphones in a compact, easy-to-grip case. Sized especially to stack behind your 4.3in smartphone for uninterrupted phone-use while charging. An LED column lets you know just how much juice is left without diverting attention from your work.

Say goodbye to knots.

Who doesn't hate tangled cables? With an intuitively-sized micro USB cord for Android, the Slim2 allows you to carry your power all-in-one. Using an iPhone? Plug into the USB port and charge up via your OEM cable.

No expense to speed.

What's better than a high-capacity battery that slides into your pocket on-the-go? One capable of simultaneous, full-speed charges. Both ports supply 1A of power with complete safety to your phones, so you can power up in no time and make the most of your day.

Customer Reviews

  • Perfect
  • Great mobile phone battery charger. Works perfectly with my HTC Desire.
  • 2014-10-18

Amazon Customer
  • Good quality and great prices
  • Lost my first Anker and replaced it with another. Good quality and great prices.
  • 2014-10-17

Bryan Day
  • Perfect Balance Between Capacity and Usability
  • I've had a few external battery packs over the last few years. The Anker Astro E3 10k (which I currently have and love for its capacity) and a few others. All of them suffered 2 flaws in my go-to use case- Had to use a separate cord to charge devices, which meant carrying around a cord and possibly having said cord be damaged when in use and in a bag- Be too large and/or bulky to carry around in a pocketThe Slim2 Solves both of these issues. I can easily pocket this device (front or back pocket) and have it ready for use if I don't have my daily bag with me (late nights out whaaaat?). As much as i love the E3 it's a bit bulky and cumbersome when I carry it by itself. The Slim2 also satisfies my desire to not have to carry an extra cord. Neatly tucked away, the cord is there, when you need it. Granted, I have a Samsung Galaxy S5, so i can use the built-in micro-usb. I also like how it detects when plugs in and doesn't have to be manually turned on.I chose the 4500mah version since i usually have my E3 10k with me if I'm traveling so this serves the purpose of a 1-1.5 charge item that i can make it through a day or weekend with if I don't have a charger available. As crazy as that sounds, it happens.Definitely recommend this for anyone looking in the 1-2 charge range. Larger devices are out there for 5+ charges worth of capacity, but this isn't looking to suit that need. Plus, cable not needed!
  • 2014-10-14

Bill in CowTown, CA
  • Great product. Simple to use
  • 2014-10-10

Shawn M. Ross
  • Works great. Holds a charge well and charges the devices ...
  • Works great. Holds a charge well and charges the devices I own. I would say you could could charge your smartphone 3 times off of one charge on this. Love the built in micro USB.
  • 2014-09-24
<< < 1 2 3 4 5 6 7 8 9 10 > >>

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.  Can charge multiple devices simultaneously?
Yes, it can charge two devices simultaneously.
Q11.  What if the Astro Slim2 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.
Q12.  What if the Astro Slim2 fails to charge my devices?
Refer to the tips listed under Question 3, and check that the Astro Slim2’s voltage is compatible with your device's required charging voltage.
Q13.  How long does it take to fully charge this Anker external battery?
5-6 hours with a 1A output adapter.
Q14.  What do the LEDs indicate when the external battery is charging itself or other devices?
The LED lights will remain on until the connected device is fully charged or disconnected. When the Slim3 is recharging, the LED indicators will display the charge level. The LEDs will turn off automatically once the battery is fully charged.
Q15.  How can I tell whether the Astro Slim2 is charging or discharging?
The Astro Slim2 is designed with auto on / off settings to simplify operation. It will begin charging or discharging once the cable is connected.

You may also like

Feel free to ask questions about this product here.
Your question will be posted on this page.
Anker Customer Support and the Anker user community will do their best to quickly answer your question.



Please enter the verification code - humans only!*


Latest Post

Charging speed
I see this pack provide 2A of total output.  Can built-in micro usb cable output the total 2A?
Replies(2) Collapse Report as spam Oct 14, 2014 at 6:08 PM
Justin Rohr
According to the site above " Both ports supply 1A of power " which means that the cable will only supply 1A of power, although depending if they limit it, it could supply more as the pack supports 2A total
Reply Report as spam Oct 14, 2014 at 8:55 PM

The Slim 2 has a max output of 1A and the output of the USB port and the built in cable is the same.
Reply Report as spam Oct 14, 2014 at 9:00 PM
For iPhone
Is there ever going to be one of these made in the lightning connector on it?
Replies(1) Collapse Report as spam Sep 15, 2014 at 12:59 PM

Unfortunately not.

We're finding that built in cables are not what our customers are looking for, they prefer the option to plug any cable in the output ports.
Reply Report as spam Sep 15, 2014 at 8:30 PM
Nexus 5

Can anyone tell me if this is compatible with Nexus 5 and how many charges could I possibly get from it??...I couldn't see Nexus 5 specified anywhere. Thanks.

Replies(6) Collapse Report as spam Apr 27, 2014 at 5:35 PM

It's compatible, it just needs to have a USB cable, if it does it should charge off it - that's the rule for phones anyways.

It'll charge your Nexus 5 about 1.5 times.

It should be about 80% efficient at least so .8 * 4500 = 3,600 mAh+
So 1.5 charges, at least, and close to 2 (around 1.8).

Reply Report as spam Apr 28, 2014 at 12:11 AM
Fire and Ice

will work with no problems! 

Reply Report as spam Apr 28, 2014 at 1:31 AM

The Astro Slimtalk will output only 1A. If your Nexus 5 require higher than 1A charging, I would suggest to get a different model that can output more than 1A like the Astro 3E, E4, E5 or the 2nd Gen.

Please let us know if there is anything else we can assist. Thank you.

Reference Ticket#712329 if contacting a CSR by phone.
AnkerDirect Customer Support
Mon-Fri 9am to 5pm(pst)

Think our Customer Service is top notch or needs improvement? Please share your thoughts by clicking here!

Reply Report as spam Apr 28, 2014 at 6:30 PM
Haninder Singh
Quote From ros:fgfgfgf
Reply Report as spam Jul 2, 2014 at 2:31 AM
Quote From Haninder Singh: jhjdhsj
Reply Report as spam Jul 2, 2014 at 4:24 AM
Reply Report as spam Jun 27, 2014 at 1:04 AM
What is the weight of the Anker® Astro Slim2 4500mAh ??
Replies(6) Collapse Report as spam Mar 9, 2014 at 9:30 PM
As stated on this page at the top under the heading weight it is 113g / 3.9oz. Did you have another question?
Reply Report as spam Mar 10, 2014 at 12:56 AM
IT Owl
Quote From gherardini: Man what kind of bread are you eating haha? Definitely not wonderbread :P Must be those fancy baked european loaves haha
Reply Report as spam Mar 10, 2014 at 1:08 PM
No Wonder bread here. Just the kind that goes well with cheese.
Reply Report as spam Mar 10, 2014 at 1:18 PM
David Hocutt
Mine is so light I have to literally tape it down or it will float way. You have no idea how many times I've had to climb a ladder and pluck it from the ceiling. No, seriously...
Reply Report as spam Mar 10, 2014 at 7:15 AM
113 grams? That's seriously lightweight, like a slice of bread....
Reply Report as spam Mar 10, 2014 at 8:59 AM
IT Owl
Weight 113g / 3.9oz
Reply Report as spam Mar 9, 2014 at 11:15 PM
too "clever" of a design
This is a great form factor for a charger product, but unfortunately Anker was a little too clever with the micro usb tether that comes out of the charger that you plug into your phone to charge it. The housing surrounding the port is huge relative to what a normal micro usb cable sheath is, and the micro usb male adapter itself isn't long enough, so it requires me to pull my case off my nexus 5 in order to charge it. I really wish Anker would have done more real world homework on this design; they would have easily seen that anyone with any case on their phone wouldn't be able to use it. My case is the google nexus 5 case and is only a couple mm thick so it's one of the slimmest cases around and it doesn't work. Other than that huge annoyance, the charger works as expected.
Replies(4) Collapse Report as spam Feb 21, 2014 at 6:56 PM
Here's the good news. Anker actively reads these forums and from first-hand experience I know they listen to reader feedback. You make a good point ... sometimes even the best companies can't think of everything until people like you point out areas of improvement.
Reply Report as spam Feb 22, 2014 at 1:30 AM
Nexus 5 owner here too using the same battery pack. However, I don't have a case on mine and the usb adapter fits. Sorry you have to take your phone out of its case every time you want to use this battery pack to charge it.
Reply Report as spam Feb 24, 2014 at 6:49 PM
Pavel Petukhov

Depending on your case, you cannot expect it to fit into each and every port. I believe there are plenty of rugged case that would allow you to charge your device unless it is taken out of the case. I have no problems with using this device to charge my Nexus 4 when in case. 

Reply Report as spam Apr 15, 2014 at 6:07 AM
Haninder Singh
Reply Report as spam Jul 2, 2014 at 2:34 AM
What are the number of charging cycles of this model and the astro slim 3? by charging cycles i mean how many times can it be charged and discharged?
Replies(4) Collapse Report as spam Feb 19, 2014 at 1:12 AM
IT Owl
Over 2000 time maybe twice that
Reply Report as spam Feb 19, 2014 at 1:41 AM
Li-Ion battery performance is rarely specified over more than 500 cycles. Depends on how often you use it
Reply Report as spam Feb 19, 2014 at 3:10 PM
It should be 500 or more, it depends on how you use and charge it.
Reply Report as spam Feb 19, 2014 at 6:53 PM
Or maybe it's just 500 or so, depending on how you use it.
Reply Report as spam Feb 21, 2014 at 10:54 AM
Nexus 4
Can anybody please tell me how many times can the astroslim 2 charge a nexus 4?
Replies(4) Collapse Report as spam Feb 14, 2014 at 5:52 AM
1.5 - 2 full charges, it will depend if you'll be using your phone while charging.
Reply Report as spam Feb 14, 2014 at 6:47 AM
IT Owl
Reply Report as spam Feb 14, 2014 at 9:43 AM
Manan Ghelani
What are the number of cycles for which we can charge and discharge it?
Reply Report as spam Feb 16, 2014 at 12:24 PM
Manan Ghelani
Quote From orthopaedicsurgeonWhat are the number of cycles for which we can charge and discharge it?
Reply Report as spam Feb 16, 2014 at 12:25 PM
my favorite.....
I've tried a lot of external batteries and i can tell that this is my favorite. very thin and light, i can do more that 2 charges to my iphone 5. love it!!!
Replies(2) Collapse Report as spam Dec 17, 2013 at 5:44 PM
Thanks for the review. You're right about the charge. Should be able to charge an iphone at least twice to keep you going through heavy power use work days. Please contact anker support if you have any questions or concerns
Reply Report as spam Dec 17, 2013 at 10:09 PM
Yeah, I was thinking about getting it for me and Galaxy S3 because of its thinness and how much juice it packs.
Reply Report as spam Feb 15, 2014 at 11:26 AM
Slim and Easy
I used this on a recent trip to recharge my iPhone 4 twice from about 40%. It still had juice left after that. I had to use my own iPhone cable but I bet this would be perfect for Android users. It fits easily into a tight pocket in my travel bag. It recharges quickly. Really, what else could you want from a slim portable battery?
Replies(3) Collapse Report as spam Nov 6, 2013 at 2:50 PM
That is true, the only thing I have that is a concern is I think the plug that comes out to charge an Android is too big for my case. That's why I'm deciding whether to buy it or not.
Reply Report as spam Nov 6, 2013 at 4:57 PM
Quote From AnkerMember431: the slim size was such a big factor for me, I didn't mind using my own charging cable. Another option is to utilize another case/cover for your phone.
Reply Report as spam Nov 6, 2013 at 7:45 PM
That's true, I think I might get it and use the wire that comes with it. Is that not a micro usb as well?
Reply Report as spam Nov 6, 2013 at 10:35 PM
No charger
I didn't receive a charger with my Anker Slim 4500 power bank. Can I get a charger sent to me? Can I use another charger? Thanks
Replies(2) Collapse Report as spam Oct 31, 2013 at 8:57 PM
The Astro Slim doesn't come with a charger as it can be charged with any USB power adapter or a computer or laptop's active USB port. Hope that helps!
Reply Report as spam Nov 1, 2013 at 3:42 AM
You can use any charger/power adapter as long as it supports USB charging. I use this Anker charger to power up my Anker Slim
Reply Report as spam Nov 1, 2013 at 12:48 AM
<< < 1 2 > >>

Back To Top

Submit your email address here to subscribe the latest information regularly about our promotion activities and new products.

Thanks for taking the time to visit our site. If you have general questions and suggestions, we’d love to hear from you through the form below.
For more specific inquiries relating to customer service, wholesale, or media requests, feel free to visit our contact us page.