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iPhone Battery Freedom: The Griffin PowerDuo Reserve and the JustMobile Gum Pro

Those who follow me on Twitter or on Facebook know that I use my iPhone 3GS an awful lot. Whether surfing the internet, tweeting, reading up on news, or responding to e-mail, I’m engaged with it at all times. This has frequently become a problem due to the iPhone’s limited battery life.

The iPhone 3GS is rated for 5 hours of talk time on 3G and 5 hours of internet use on 3G (10 hours on wifi, which is less frequently available to me). As such, if I leave my home with a full charge in the morning, I’m typically in need of a battery boost by mid-day. Finding an outlet and sitting around waiting for my phone to charge is usually not possible and would not be a good option even if it was possible.

Enter portable battery pack options. Today, I’ll be describing my anecdotal experiences with two battery packs: The Justmobile Gum Pro and the Griffin PowerDuo Reserve.

The $60 Justmobile Gum Pro comes in a horrible cheap-looking box and looks like the most low-rent knock-off battery pack ever. Nonetheless, it contains a small battery with a pretty powerful charge inside. Rated at 4400 mAh, this thing has the potential to recharge your iPhone to completion more than 3 times. It sounds like any iPhone user’s dream come true: Never worry about needing an iPhone charge ever again (theoretically)!

In practice however, the process of using it is actually moderately cumbersome. In order to charge it, you have use a USB cable to connect it to a power source. I had been under the impression that this charging process would just take a few hours, but in my experience, using a variety of USB charging devices plugged into electrical outlets, it has taken about 6-8 hours to charge this thing.

So then you have to carry around the Justmobile Gum Pro with you (it feels like it weighs about 1/3 to 1/2 a pound) and when the time is right, you connect an iPod cable from the Justmobile to your iPhone. This is a little bit difficult to do on the go. I have an elaborate system worked out with the pockets in my jacket that makes this situation bearable; the sight of me holding my iPhone with a white iPod cable snaking out of my pocket is not uncommon. However, those who do not may find that the Justmobile Gum Pro is an embarrassment to take out in public with you. It’s also really difficult to hold the Justmobile Gum Pro AND the iPhone with one hand (hence necessitating the pockets).

One other thing: I have found that the Justmobile Gum Pro’s battery charge has degraded significantly over time. While it once could charge my iPhone 3+ times, it now struggles to get to barely two full charges before it needs to be plugged in again.

The PowerDuo Reserve package is a different sort of deal altogether. For $60, you get a car charger, an AC adapter/charger, and a small little battery pack that plugs straight into your iPhone.

The AC adapter and car charger have obvious utility, and if you need those items, they alone justify the cost of this package. However, the spare battery pack is a neat little addition that is great at helping you out in a pinch. It has LED indicators that activate when you press the one button located on its face. These indicators tell you how much charge is left. The build quality is great and the best thing about it is that the battery pack is light and not too big, so it won’t weigh down on your iPhone connectors. When plugged into your iPhone, the device is virtually unnoticeable.

The big caveat? The spare battery pack only charges your iPhone about 20%. This is a miniscule amount of charge compared to what the JustmobileGum delivers.

In summary…

The Justmobile Gum Pro:
Cost: $60

  • Can completely recharge your iPhone multiple times.


  • Packaging does not inspire confidence, looks like it was made in a sweatshop
  • Charge degrades over time
  • Recharging the Justmobile Gum Pro takes a really long time (usually must be done overnight)
  • Requires cable to charge your iPhone

The Griffin PowerDuo Reserve
Cost: $60

  • Lots of charging options (i.e. good value for money), although they require electrical outlets
  • Excellent build quality and packaging
  • Almost completely unobtrusive to your iPhone experience


  • Only recharges your iPhone about 20%


Ultimately you will have to weigh what you need most with how much money you have to spend. Need more electrical outlet charging solutions, plus a nice little battery boost when necessary? The Griffin PowerDuo reserve is a good option. Primarily concerned with sheer battery power? Then go with the Justmobile Gum Pro.

As for me? I carry both of these things around with me at all times. Sure, it’s a pain in the butt to have to make sure they’re both charged at all times. But is it worth never having to worry about my iPhone’s battery, ever? Hell yes.

I received a review unit of the Griffin PowerDuo Reserve for the purposes of this blog post. I purchased the JustMobile Gum Pro myself.

Want to send me a product to review? E-mail me at davechensemail(AT)gmail(DOT)com.