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Anker PowerCore II Slim 10000 Review

This is a solid, all-around portable battery but we wish it had a few more convenience features
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Price:   $36 List | $30 at Amazon
Pros:  Highly portable, recharges quickly, decent capacity
Cons:  Pricey, bare-bones
Manufacturer:   Anker
By David Wise and Austin Palmer  ⋅  Oct 25, 2018
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#6 of 15
  • Portability - 40% 8
  • Capacity - 30% 5
  • Added Convenience - 20% 3
  • Recharge Time - 10% 7

Our Verdict

While the PowerCore II Slim 10000 by Anker couldn't quite clinch one of our awards, it still finished close to the top. This bare-bones charger is super easy to carry, has a solid capacity, and recharges quickly, making it a great option if you need to make sure you can get a few charges out of your battery. However, it does have quite a deficit when it comes to features, precluding it from one of the top spots, as well as by being a bit on the more expensive side. Overall, this is a good, medium-sized battery pack that is large enough to get a handful of charges but is small enough to easily carry with you.

Compare to Similar Products

Our Analysis and Test Results

This portable battery outperformed the OtterBox Power Pack 10000, but fell short of the Anker PowerCore 5000. The PowerCore 5000 did a bit better in our capacity test and is slightly more portable, though it also lacks any convenience features, giving it an edge over the PowerCore II Slim. It also retails for about half the cost. The OtterBox is less portable and more expensive than the PowerCore Slim, giving the edge to the Anker overall, but does seem a bit more durable and rugged, making it a product to consider if you are planning on taking your battery on some outdoor excursions.

The PowerCore Slim 10000.
The PowerCore Slim 10000.

Performance Comparison

To pick out which portable chargers are really the best out there, we looked at dozens and dozens of different products, then bought the most promising and tested them head-to-head. We split up our testing process into four weighted rating metrics, with the Anker PowerCore II Slim's standings and performance discussed below.

The PowerCore II Slim 10000 also fits quite well in a pocket.
The PowerCore II Slim 10000 also fits quite well in a pocket.


When it came to portability, the PowerCore II Slim 10000 scored quite well, earning an 8 out of 10. This metric is based on how easy it is to carry each battery pack, its volume, and its weight, with this trio of tests combining to account for 40% of the total score.

The PowerCore II Slim is a rectangular battery pack that is quite easy to hold, being about 5.4" long and 2.6" wide. Additionally, this battery has an astonishingly thin profile, measuring in at only 0.6" thick — hence the "Slim" in the name.

This battery pack is also on the lighter side compared to the rest of the group, weighing in just shy of 7 and a half ounces.

The slim profile on this battery made it one of our absolute favorites to carry around it a pocket. It fits well both sitting or standing, either in a front or back pocket, and is so hardly noticeable that it is easy to forget that it is even there.

We weren't able to even get close to the claimed capacity in our test.
We weren't able to even get close to the claimed capacity in our test.


For our next round of tests on each battery, we compared the electrical capacity of each battery, both by using a digital electrical meter and dummy resistive load, as well as by charging various devices. Altogether, these tests account for 30% of the total score for each portable power pack.

Using our dummy load set for a 2.4 amp discharge rate, we were able to pull approximately 5892 mAh out of the Anker PowerCore II Slim before it completely died, or about 59% of its stated capacity. We did this test again with the load set for a 1 amp discharge and were able to get about 69% of the stated capacity out of it. This put the Anker PowerCore II slightly below average, when compared to the other batteries of the group.

The 10000 can charge most smartphones a few times.
The 10000 can charge most smartphones a few times.

This battery pack also fell slightly short of its manufacturer's claims, which stated that you should be able to get 2.2 Samsung Galaxy, 3.6 iPhone 8, or 2.4 iPhone X charges out of it before dying. We used a Galaxy phone to test and were able to get two full charges and get the phone up to 12% on the third try, rather than the expected 20% before the Anker PowerCore II Slim completely died.

This battery can only charge a single device at a time.
This battery can only charge a single device at a time.

Added Convenience

Accounting for 20% of the total score, our convenience tests came next in terms of importance. We compared the various integrated features on each battery pack, as well as the included warranty and the number of output ports on each portable power pack to determine scores for this metric, with the Anker PowerCore II Slim meriting a 3 out of 10 for its bare-bones design.

This battery pack includes a micro USB cable and comes with an 18-month limited warranty, but that's about it when it comes to convenience and ease of use.

The Anker doesn't have an integrated plug for recharging or any built-in cables for different devices. It also lacks a built-in flashlight and can only charge a single device at a time.

This battery recharges fairly quickly with a high-quality power brick.
This battery recharges fairly quickly with a high-quality power brick.

Recharge Time

For the final tenth of the score, we graded how long it took for each portable power pack to recharge, using the LED indicators to determine when the battery was completely full. The PowerCore II Slim did quite a bit better in this metric, improving considerably on its performance in the previous metric and earning a 7 out of 10.

Using a fast-charging wall USB adapter, it took a little over four and a half hours to charge, making it slightly faster than the average charge time.


This pack isn't overly expensive, but it isn't the best value you can get, with other batteries giving you a better bang for the buck.


While the Anker PowerCore II Slim didn't earn any awards, we still were quite fond of this battery. It's easy to carry and is a great option if you want more capacity than the PowerCore 5000, ensuring you get at least two full phone charges or that you can fully charge two different devices, provided they aren't too large.

David Wise and Austin Palmer