I've never met anyone who is completely satisfied with the battery life of his or her mobile device. And now that the, you'll need even a few minutes more of juice.
The good news is there's a plethora of battery packs (aka juice packs) that now offer you many ways to conveniently carry extra power with you. The following are my favorite juice packs (yes, I have a lot of favorites) that, when paired with a mobile device, are great not only for long flights, but also when you're out and about camping or hiking, even in rough environments. It's always great to have one or two of them in your car, just in case.
Note that I haven't officially tested and reviewed these devices (at least, not all of them) but via personal and collective experiences, I consider these among the best on the market. In any case, if extra battery life for a smartphone is what you want, you won't go wrong with any of these.
This is my favorite juice pack. This compact battery packs 7,800mAh of power, enough to charge an iPhone from empty to full about three times and still have juice left. On top of that it can also work as a flash light or a portable lantern for up to 48 hours straight. In my testing, it wasn't really bright (64 lumens), but it's bright enough for reading or if you need to replace a flat tire in the dark. What I love the most about it is the design. The top can be pulled up to work as a lantern and when pulled down, it's a flashlight. If you're a camper, it's great to hang it on top of your tent. The SmartLantern is available on Amazon for $60. There seems to be another version of it that's about half the price.
At 20,400mAh, this is one of the highest-capacity juice packs I've seen. The Optimus can easily provide two full charges to most tablets and about eight full charges for most smartphones. In my testing it could provide about 10 charges for my iPhone 5, basically enough juice for me to survive outdoors for more than a week. You can charge two devices at a time and on a side, the Optimus incorporates a little flashlight that's bright enough for you to take a walk in the dark to look for your phone that you left somewhere in the tent. In all, it's quite worth the current $130 price-tag.
Mophie Space Pack
This is a juice pack for the iPhone 5/5S only. Apart from offering another 1,800mAh of battery life (almost another full charge), this juice pack also works as a protective case and a storage extender. It's not cheap, though, costing about $150 or $180 for 16GB or 32GB, respectively. On top of that, in my experience, protective-case juice packs tend to lower the phone's reception quite a bit. But if you're looking to add more storage to your iPhone, this is about as convenient as it gets. Read more about the Mophie Space Pack here.
Tenergy ARC5200 Universal Mobile Power Pack
For just $50 on Amazon, the Tenergy ARC5200 seems an excellent deal. This juice pack is compact, just about the size of an energy bar, but it packs a 5,200mAh battery, enough to refill an iPhone 5's battery more than twice. The best thing about the Tenergy is the fact that it has two built-in charging cables, one with a Lightning head for an iOS device and the other with a standard Micro-USB head that fits most other mobile devices. These two cables are tucked away on the side of the juice pack when not in use and can be pulled out easily, allowing you to charge your device even when you forget the charging cable at home. And yes, it can charge two mobile devices at a time.
The HooToo TripMate is not just a juice pack, it's also a mobile Wi-Fi router that can convert any wired network to wireless with the support for 801.11n. It can also host a portable USB storage device and work as a network storage server to host data shared between connected clients. With a 5,200mAh internal battery, this little device can also provide plenty of power for any mobile devices. With this Swiss Army Knife-like approach, almost any traveler will find a use for the HooToo, which can be had for just $50 on Amazon.
The Samsung LTE HotSpot Pro
Similar to the HooToo above, the Samsung is actually not a juice pack; rather, it's a mobile cellular modem that brings the Internet to up to 10 Wi-Fi-enabled devices (and it works very well in that regard). However, this is also the first device of its type that comes with a very powerful 3,100mAh battery that, apart from giving the device itself some exceptional battery life, can also work as charger or a juice pack for any smartphone or tablet that uses a standard USB charger. In my testing, the Samsung, when fully charged, packed enough juice to bring an iPhone 5 from empty to full and still had some power left. More impressively, it did that while working simultaneously as a mobile hot spot. If you're also looking for a mobile hot spot, the Samsung definitely makes an excellent solution.
Lenmar Meridian iPhone 5/5S Rechargeable Extended Battery Case
If you have multiple mobile devices, be they tablets or smartphones, the Satechi 10,000mAh Portable Energy Station is for you. This is a compact 10,000mAh battery pack that can charge two devices simultaneously. It has enough power to fully charge an iPhone 5S from empty about four times. It can be used to charge virtually all mobile devices that use USB charging. Measuring just 5.5 inches by 2 inches by 0.75 inch and weighing just 7.4 ounces, the Satechi is supercompact for the amount of power it carries. Make sure you charge it overnight before your trip, however, since it takes up to 9 hours to fully charge itself. The Satechi 10,000mAh Portable Energy Station currently costs just $60 on Amazon.
Lenmar Meridian iPhone 5/5S Rechargeable Extended Battery Case
The Lenmar Meridian iPhone 5/5S juice pack, as the name suggests, works only with the iPhone 5 and 5S. It packs a 2,300mAh battery, and that means it has enough power to double the battery life of the phone. Apart from being a juice pack, it's also a protective case that you can use with your phone permanently. In this case you can sync or charge the phone using a standard Micro-USB cable. The juice pack also includes a headphone extension cable. Currently the Lenmar Meridian juice pack goes for just a little over $50 on Amazon.
Joos Solar Orange Portable Solar Charger
At almost 1.5 pounds and about a size of a regular-size book, the Joos Solar Orange Portable Solar Charger is not something you want to use on a flight but rather for a long road trip or when working out in the wild. Claimed to be one of the most efficient solar chargers, the device is said to offer 2 hours of 3G talk time for each hour of direct solar charging. On top of that, it comes with a built-in 5,400mAh battery to continue to charge devices when the sun is down. This battery can be charged via a wall socket like any juice pack and takes 8 hours to fully charge from nil. When charged using the sun, it takes about 12 hours. The great thing about this juice pack is the fact that it can deal with rough environments and can even work underwater. The Joos Solar Orange Portable Solar Charger can be found on Amazon for about $150.
RAVPower Luster 3,000mAh Compact External Battery Pack Backup Charger
Coming in a "lipstick" design, the RAVPower Luster is tiny, just about the size of a AA-battery flashlight, and it is a LED flashlight itself. On the inside, this versatile juice pack comes with a 3,000mAh battery, more than enough power to fill an iPhone 5 from empty, and it can provide extra power to most mobile devices. The device itself takes about 5 hours to charge from empty to full using a standard USB adapter (or a computer's USB port). At just $20, the RAVPower Luster 3,000mAh Compact External Battery Pack Backup Charger is a steal. And the fact that it comes in multiple colors, including pink, is a bonus.
Anker 2nd Gen Astro3 12,000mAh Portable Charger
The long name says it all. This is a battery pack that comes with a 12,000mAh internal battery, enough power to charge an iPhone to full from empty six times. Considering the compact size -- just 4.4 inches by 3.3 inches by 1 inch and weighing just 10.6 ounces -- this is arguably the most powerful juice pack of its type. The Anker comes with three USB ports to charge three devices at a time, and is able to charge virtually all mobile devices, including larger ones, such as an iPad or a Samsung Galaxy Tab 10.1. The juice pack itself takes about 9 hours to fill up from empty, so make sure you start charging it well before your trip. The Anker 2nd Gen Astro3 12000mAh Portable Charger is available on Amazon for just $50.
RAVPower Element 10,400mAh External Battery Pack Charger
With a 10,400mAh internal battery -- enough juice to charge an iPhone from empty more than five times -- the RAVPower Element is just a tad less powerful than the Anker above. And more than making up for it, it costs just $30 on Amazon. The juice pack can charge any mobile device, including those with large screens, two at a time. Just slightly wider and thicker than the iPhone 5, the RAVPower Element can be easily tucked away in any backpack or purse.