Just Mobile Gum Max Battery Pack Review

Gum Max Review (17)

Imagine you could create the ultimate external battery: what features would choose and how should it look like?  For me it would probably be something along the lines of the Just Mobile’s Gum Max with its huge 10,400 mAh capacity, aluminum-clad and a total of eight LED lights to give you  detailed info on remaining power. While it definitely has plenty of juice, that’s hardly enough to call it the ultimate external battery. It does however offer a strong mix of features allowing it to come close. The question is: Just how close?



Compatible with all iPads

2.1A output

10,400mAh Li-Ion battery

Apple certified – works with iPad, iPod and iPhone

Apple dock connector and USB-to-microUSB cables included

Travel pouch included

High-grade aluminum shell


8.3 x 11.0 x 2.6 cm

3.3 x 4.3 x 1.0 in

Design Object No.:  PP-818

The Just Mobile Gum Max Battery Pack

Gum Max Review (13)

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The Gum Max is Just Mobile’s top of the line external battery, offering an impressive 10,400 mAh capacity. We’re still not sure what the “Gum” stands for, but what we do know that it’s the name given to their series of external batteries with which includes the Gum,  Gum Pro, Gum Plus and Gum Max. The Max is not only larger than the $90 Gum Plus, but it also offers twice the capacity for about $20 more, making it the better deal among the two.  One serious competition to the Max however is the i.Sound Portable Power Max 16,000 mAh Backup Battery, which for $130 dollars offers 16,000 mAh, can charge 5 devices at a time and includes a power adapter, an important accessory the Max lacks.  Nevertheless, the Max clearly wins when it comes to design, materials and overall build quality. While the i.Sound offers more features and larger capacity, the style conscious consumer will clearly prefer Just Mobile’s offering.

The Max is currently only available in Silver, odd considering  their other external batteries are also available in Red, Platinum and Black. We’d love to see it in more colors, especially in Black. But in the  meantime you can have the Gum Max, just like Henry Ford said in any color, but in this case, as long as it’s in Silver.

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Moving on to the features, the Max has a handy  5V/2.1A output, which should be enough for even the most power-hungry devices such as tablets, albeit only a single device can be charged at a time.

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One major down side surrounds the charging of the Max itself which requires an equally hefty  5V/2.1A power source. To make matters worse such an adapter isn’t included,  something we’d expect from a product of this caliber. As a result you’ll need to use one of Just Mobile’s recommended power sources which include the iPad’s 10W USB power adapter, the USB port on a more recent MacBook Pro, MacBook Air, their own Just Mobile Highway car charger or simply buy a 5V/2A adapter.

This somewhat limits the Gum Max’s usefulness to Mac and iPad owners, leaving Window users and owners of other mobile devices out in the cold, unless you’re planning on shelling out even more cash after spending that $110. And as I’ve learned, these 5V/2A chargers aren’t easy to find and quite expensive. In the end I settled on Belkin Power Adapter which did the trick.

Just Mobile Gum Max 1

There’s a reason why many computers and notebooks are excluded. The manual even warns “do not connect Gun Max to a USB power port of a computer/notebook as it is not powerful enough to recharge the Gun Max.” I tried charging the Max by connecting it to my Sony VAIO Z which confirmed what was said in the manual: it simply won’t charge. Apparently the USB ports on most Windows-based computers don’t provide enough juice to charge the Max, but recent Mac devices should do the trick. Just be aware that even on the Mac you may encounter some problems as some users report receiving a notification stating that: “Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled. To prevent damaging your computer, the USB device drawing too much power has been disabled. Other devices may have also been disabled. When you disconnect the device drawing too much power, your other USB devices will be enabled again” All of this could have been prevented by the inclusion of a power adapter, something Just Mobile should seriously consider. The lack of an adapter that can keep up with the power needs of the Max is just one of few downsides to the Max.

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The Max comes in Just Mobile’s typical stylish all-black package and includes a USB charging cable, a Dock Connector cable and travel pouch. We’re happy about the inclusion of the pouch as Aluminum tends to scratch quite easily. Like we’ve mentioned above, only thing really missing is a power adapter.

Gum Max Review (15)

Gum Max Review (1)

Just Mobile calls their products “Design objects” and it’s easy to see why. The aesthetics, quality materials, in particular the use of aluminum and design play an important role when it comes to their products. The Gum Max is no exception. The aluminum-clad Max is  about the size of a portable hard drive, although twice as thick. It’s definitely not heavy, but has quite some heft to it that in combination with the overall fit and finish simply exudes quality. The design can be described as very minimalistic and undeniably inspired by Apple products with its Aluminum shell in combination with a Black plastic strip that runs along the entire middle part.

Gum Max Review (2) Gum Max Review (3)


The only features found on the upper side of the Max are the  8 LED lights and a single button to activate charging. The LED lights glow a soft Light green that adds to the overall quality feel and design of the product. Many designers seem to get the design right, only to make all the wrong choices when it comes to the LED lights which when are too bright, have colors that don’t fit the design and materials can take away from the overall design. On the Max, even the way the LED lights slowly blink when recharging the Max or when charging a device seems to have been carefully chosen. My choice for the LED colors would have been a soft White glow, but the Green does the trick nicely.

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One thing to be aware of is the fact that the Max  lacks an auto off feature, meaning you’ll have to manually press the power button to turn it off when your device is fully charged. Many times I’ve put my phone to charge before going to bed, only to come back to in the morning with a full battery and the Max still trying to charge the phone with blinking LED lights and all. External batteries like the Zaggsparq has this ability to detect when the device is full and turn off. This is one feature we’d love to see on future version of the Max.

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The edges have been nicely rounded and the Black plastic strips adds a nice detail and contrast to the design. The plastic strips houses both the input (microUSB) and output (full-size USB) ports. Other than the a few warnings, the Just Mobile logo, the device model name and some regulatory text, the bottom is clear of any features.

Gum Max Review (12)

The main reason to consider the Max is of course its enormous capacity. You can put any ridiculously large amount in an external battery and you would probably it end up with a not-so-portable battery. The beauty of the Max is the balance between large capacity in a fairly compact size and having 10,400 mAh at your disposal is a real treat. For smaller devices like smartphones this means being able to up to 8 full charges, enough for an entire weekend f heavy use. My Galaxy Note for example is able to get 4 full charges from the Max, quite impressive considering it’s the second highest phone battery, bested only by the Droid Razr Maxx. Admittedly having a spare batteries is a cheaper alternative, but in the case of the Max for me  that would mean buying 4 batteries which would far exceed its price. While 10,000 mAh should be more than enough, Just Mobile should consider pushing the boundaries by making it at least 15,000 mAh. Even at 10,000 mAh they leaves a lot of potential untapped with just one charging port. Future versions should at least have 2 ports. Charging this beast will take some time. Using a 5V/2.1A charger I was able to fully charge it in about 6.5 hours. Charging via the USB compatible USB ports could take even longer.


The Just Mobile’s Gum Max comes close in being the perfect battery offering a striking balance between quality materials, style, portable size and plenty of power. The i.Sound Portable Power Max 16,000 mAh Backup Battery can charge 5 devices at a time and includes a power adapter, an important accessory the Max lacks, making it the better deal.  Nevertheless, the Max clearly wins when it comes to design, materials and overall build quality. While the i.Sound offers more features and larger capacity, the style conscious consumer will clearly prefer the Max. The biggest downside to the Max is the lack of an included power adapter, leaving many Windows users and those without an iPad in the cold. If Just Mobile manages to include the charger, add a second USB output port and and give it a capacity of around 15,000 mAh this could very well be the best external battery on the market. In the mean time it comes close enough and gets an 8 out 10.


5V/2.1A output charges the most power-hungry devices

Plenty of charge capacity allowing multiple charges

Beautiful minimalistic design

Aluminum clad

Good fit and finish

8 LEDS provide a good indication of remaining power


No included power adapter           

Very power hungry: won’t charge from most Windows based laptops/PCs

Can only charge one device

Can’t automatically detect when a device is full and turn off.