The Best External USB Battery Review

Click to enlarge
Credit: Chris McNamara
Which external battery is the best to power your USB devices such as a cell phone, camera, or other devices? To find out, we selected nine of the top rated and most popular models to find out how they compared in side-by-side tests. We used them them on planes, road trips and around the office and rated each on capacity, output power, weight and ease of use.

You may also be interested in our related review category: Solar Chargers.

Read the full review below >

Review by: and Ryan Edwards

Top Ranked External USB Batteries Displaying 1 - 5 of 9 << Previous | View All | Next >>
Our Ranking #1 #2 #3 #4 #5
Product Name
Anker 2nd Gen Astro2 9000mAh
Anker 2nd Gen Astro2 9000mAh
RAVPower Element 10400mAh
RAVPower Element 10400mAh
Maxboost Electron 10000mAh
Maxboost Electron 10000mAh
OXA Frosted Box F1
OXA Frosted Box F1
Powertraveller PowerGorilla
Powertraveller PowerGorilla
Editors' Awards  Editors' Choice Award      Top Pick Award   
Street Price $37 from Amazon$25 from Amazon$27 from Amazon$114 from Amazon$250 from Amazon
Overall Score 
100
0
76
100
0
75
100
0
68
100
0
64
100
0
63
Pros Great input and output power, easy to hold, compact, good valueGood value, charges two devices at once, strong output powerDigital battery readout to 1%, flashlightCan charge most laptops, huge capacity, good valueCan charge an Apple laptop, digital battery readout, lots of storage
Cons NoneHas an input power slightly lower than competition and not easy to hold in handMust turn on the power button to charge devices, bulkier than competitionCan't charge Apple laptops, only one USB output portExpensive, only one USB output port
Best Uses Charging tablets, smartphones and most portable electronicsCharging a smart phone or tablet multiple timesFor folks that want a very accurate readout of remaining power and a flashlightCharging laptops (PC)Charging Apple Laptops if you can find the right adapter (sold separately)
Weighted Scores Anker 2nd Gen Astro2 9000mAh RAVPower Element 10400mAh Maxboost Electron 10000mAh OXA Frosted Box F1 Powertraveller PowerGorilla
Capacity - 25%
10
0
6
10
0
6
10
0
6
10
0
10
10
0
8
Output Power - 25%
10
0
8
10
0
8
10
0
5
10
0
10
10
0
10
Weight - 40%
10
0
8
10
0
8
10
0
8
10
0
1
10
0
2
Ease Of Use - 10%
10
0
9
10
0
8
10
0
8
10
0
10
10
0
10
Product Specs Anker 2nd Gen Astro2 9000mAh RAVPower Element 10400mAh Maxboost Electron 10000mAh OXA Frosted Box F1 Powertraveller PowerGorilla
Battery Capacity (mAh) 9000 10400 10000 30000 21000
Output Power 5V/3A 5V/3A 5V/2.1A 19V/3.5A, 5V/2A 5-24V, ?
Input Power 5V/1.2A 5V/1A 5V/2A 19V/3.5A
USB Ports 2 2 2 1 1
Manufacturer Weight (lbs) 0.55 0.5 0.5 2 1.54
Flashlight? No No Yes No No
Size (inches) 4.2 x 2.5 x 1.0 4.4 x 2.76 x 0.83 4.25 x 2.8 x 0.8 9.8 x 7.1 x 3.9 8.5 x 5.1 x 0.7
Charge Laptop? No No No Yes Yes
Warranty 18 Months 18 Months 12 Months 1 year

OutdoorGearLab Editors' Hands-on Review


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Selecting the Right Product
There is no one best product for all applications. It all depends on what you are charging, how light you are trying to travel and what your budget is. Below we look at the key factors to consider so you can choose the right product for your needs.

Would you be better served by a solar charger?
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Charging the ReVolt from our Best Buy award winner, the Bushnell Solar Panel.
Credit: Chris McNamara
A solar charger or small portable solar panel is another option for charging small electronics. For most people and most applications we prefer external batteries over solar chargers. Why? The average compact solar charger will only charge a phone 1-2 times a day, and that is if you leave it in the direct sun, which is often either impossible or a nuisance. Compare that with the average external battery that is lighter and less expensive than most solar chargers and will charge a phone 2-5 times. That said, solar chargers are better for long trips away from a power source.

Some solar chargers like the Bushnell Bear Grylls SolarWrap Mini combine a battery with a solar panel. The upside to this approach is versatility; you can charge the Bushnell from a USB power source or from the sun. The downside is that it's more expensive and only holds a few phone charges in a similar size to an external battery that holds 4+ phone charges.

A third option is combine a top solar charger with a battery. This way you get the versatility of leaving the panel at home for most applications but can bring it if you might be away from a power source for 3+ days. We recommend pairing a panel from our Portable Solar review with top award winners from this review. In addition to the versatility of having the option of using the panel and charger separately, you often get a better value this way. In addition, the life span of a panel is likely to be 3-10 years. The lifespan of a battery is much shorter because you only get so many charges (often around 800) and the battery technology improves so fast that in 1-2 years you will likely want to upgrade.

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When the InstaPark Mercury 10 is paired with an external battery, it's by far the best value in a panel and battery combo.
Credit: Chris McNamara

What can you charge with an External USB Battery?
The simple answer: anything with a USB charger such as a smartphone, tablet, digital camera, GPS device, headlamp or bike light (with recharable battery), or GoPro.

The more complex answer: it depends. Some batteries can charge laptops and higher capacitiy devices, but this gets more rare and tricky. This review focuses on devices for charging small electronics. For charging larger devices, also check out our Solar Charger review.

Criteria for Evaluation
Battery Capacity - What size should you buy?
In general, the more capacity the battery has, the more expensive and heavy it is. For this reason, you want to size a battery to your needs. This is a simple three step process:
  • Step 1: Determine the size of the device you will be charging the most.
  • Step 2: Figure out how many times you want to charge your device.
  • Step 3: Multiply the size of the device by the number of times you want to charge it and make sure your external battery is big enough.

Many devices list the battery size on the product. If they don't, just Google "[device name] battery size." Here are some battery sizes for common devices:
  • 1440mAh for iphone 5
  • 2800mAh for Samsung Galaxy 5
  • 4440mAh for iPad mini
  • 4325mAh for Google Nexus 7
  • 1050mAh GoPro 3+

For example, if you want to charge an iPhone 5 four times, you want a 6000mAh external battery.

In general, we like batteries in the 9,000-10,000mAh size. This allows you to charge most smart phones 4-6 times and most tablets 2-3 times.

To charge a laptop, you will want 20,000-30,000mAh size battery.

Speed of Charging: Output Power and Input Power
To determine output power, you need to look at the volts and amps. If you are just charging a small device, you can basically ignore the volts (most small batteries charge at 5V) and just look at the amps. Our top scoring models charge at 2-3 amps which often translates to recharging your device 2-3 times faster than a battery that charges at 1 amp. For comparison, most car chargers and wall chargers charge at 2 amps.

If you are charging a larger device like a laptop, it's more complicated and not always clear whether an external battery will actually work for your needs. In addition, it can be challenging to find an adapter that will connect directly from an external battery to your laptop, especially if you are using an Apple laptop. Do your research to make sure your laptop is compatible before buying an large and expensive external battery.

Arguably as important as output power is input power or how fast you can charge your battery from a wall socket, the car, computer or solar panel. In a very competitive category like external batteries, this was a key differentiator. For example, if a battery charges at 1 amp versus 0.8 amps, it will charge 25 percent faster, which in the case of some batteries is a difference of hours.

Weight
An external battery is only as useful as it is convenient to carry. If it's too big or bulky, you are unlikely to travel with it. Our favorite models fit in a jacket pocket and weigh a half pound (8 ounces) or less (for comparison, an iPhone 5 weighs about a 1/4 pound (4 ounces). This way you can charge your phone in a jacket pocket and still have access to it.

Ease of Use
We divided the use of use rating into the following categories:
  • Does the product give a battery indicator?
  • Can you charge multiple devices at once?
  • How easy is it to charge (does it require a special adapter)?
  • How many different devices can it charge?

A clear battery indicator is very important. Only one of the batteries tested, the Maxboost Electron 10000mAh had a digital readout that let you know exactly how much charge was left in 1 percent increments. That said, we found the style on the Anker and RAVPower to be perfectly adequate (they both generally let you know the battery life in 20 percent increments.

The ability to charge multiple devices at once is essential. Even if you only have one smart phone that you need to charge, if you are traveling with anyone it is very likely they will not have a external battery and will want to use yours. This was the big differentiation between our top scoring models and the budget models; generally you need to spend $20 or more if you want to charge two devices at once.

Most of the batteries require a USB charging cable. This is a bit of a pain to keep around; we recommend always keeping the cable in your laptop bag. Luckily its standard size cable that may also charge other devices like headlamps or digital cameras (we hate having to keep track of too many different cables). The only battery we tested with a built in USB charger was the Goal Zero Switch 8. We enjoyed never having to carry an extra cable to charge it. That said, the Switch 8 scored low because it had a very low battery capacity and charges at slow rate/power level of 0.8 amps. The Switch 8 was also more than triple the price of many of its competitors.

Do you need a flashlight on the battery?
Some of the batteries we tested come with a built in flashlight feature. At first this seem cool, but we found it was rarely ever used if you already own a smartphone. Most smartphone flashlights (or the camera flash that can be turned on continuously) are as bright as the lights included in USB batteries. The one exception to this recommendation is if you are traveling light and want to avoid the hassle, weight and cost of bringing a headlamp. You can buy a flashlight holder/headband for about $7 such as the Nite Ize NPO-03-01. This turns your external battery into a slightly useful headlamp. However, if you don't mind the extra cost and weight, you can get a much higher performing headlamp for $20-36. See our Headlamp Review where we put 30+ headlamps in side by side tests.

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Attach a battery to a headband to create a headlamp alternative.
Credit: Chris McNamara

Editor’s Choice Award
Anker&reg; 2nd Gen Astro2 9000mAh
Anker® 2nd Gen Astro2 9000mAh
Credit: Anker
The Anker 2nd Gen Astro2 9000mAh wins our top honors because it was among the easiest to use, comes in a compact package and is the perfect size for charging most smartphones 3-5 times. That said, the competition was very close. The RAVPower Element 10400mAh scored nearly as high, has a slightly higher capacity and costs a few dollars less. The Anker pulled ahead for three reasons: 1) it charges faster (1.2 amps to the RAV's 1 amp), 2) it has a better battery indicator light, and 3) it just felt better in our hands. The RAV has a more slipper boxy feel and the Anker is rounded yet covered in a rubber material that is easy to hold and less prone to slipping around. A fourth reason, although a bit shallow, is the Anker just looks cooler. Behind these two was the Maxboost Electron 10000mAh. It's bulkier than the Anker and had the annoying "feature" of not charging your device until you hit the power button. It seems intuitive to us that if you have a device plugged into a battery, you want it to be charging. We often forgot the extra step of turning on the power button, which meant we would return to pick up our phone after a few hours only to find it had not been charging at all.

We recommend skipping the first generation of Anker batteries that now are outdated compared to the second generation. The first generation charges from the wall socket/car/computer at a slower rate, delivers power at a slower rate and weighs more.

While we like the 9000mAh size the best, you might prefer one of the other three sizes that the Anker 2nd Gen comes in:
  • Anker 2nd Gen. Astro 6000mAh

Best Buy Award
Ravpower luster
Ravpower luster
Credit: RAVPower
We gave our best value award to the best micro battery that costs less than $20, the RavPower Luster Mini 3000mAh. It costs only $13 and will charge an iPhone two times. It edged out the Anker Astro Mini 3000mAh because it has a higher input power of 1 amp and is less expensive. The RavPower also comes with a built in flashlight, a feature we never used but some people may appreciate. Keep in mind that neither of these have very useful charge indicator lights so if you always want a full charge, you have to pay close attention to your usage and probably charge it a little more than you think. They also only charge one device at a time. Consider them a budget way to keep your phone alive but not ideal for heavy use or charging bigger tablets or multiple devices at once. They are quite light and compact, often weighing half of what the top scoring models do. However, we find that the slightly more weight, bulk and cost of the the larger high-scoring models (described above) is worth it. For most people in most applications, we recommend boosting your budget to $30 and getting a battery with 6000-12000 mAh capacity.

Top Pick Award for Charging a Laptop
Frosted Box F1
Frosted Box F1
Credit: OXA
The OXA Frosted Box F1 was our top external battery for charging many devices including a laptop. It's about four times as heavy as the top rated chargers in our review, but if you need to charge a laptop, then you probably won't mind the weight. It comes with various adapters to charge just about anything except, to our disappointment, an Apple laptop. To do that, you need a special adapter and the Powertraveller PowerGorilla which is about double the cost of the OXA and lower capacity. One noticeable downside to the OXA and PowerGorilla is that they only have one USB port.

How We Test
We tested each of these batteries over a six-month period on road trips, plane flights and backpacking expeditions. When the cigarette lighter adapter burnt out in one of our cars, these products became our sole source of charging our phone. We also took these on an Africa Safari and used them extensively around the office (they are useful if all the USB outlets on your computer are tied up).

Chris McNamara and Ryan Edwards
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