7 hot portable mobile chargers for smartphones, tablets

You undoubtedly know people are so smitten with their smartphones and tablets that they experience separation anxiety when asked to put them away, even if it's just long enough to get through dinner. But that is nothing compared with the angst they feel when their devices' batteries are getting low.

The market for mobile power sources has grown exponentially in the last two years, with more compact and more powerful options available that allow you to recharge hundreds of times. Which one is best depends on how much power you want on hand and how much weight you are willing to carry.
First, you need to determine how much standby power you need. Battery capacity is measured in milliampere hours (mAh). The more milliampere hours a battery has, the longer it will run. Most smartphone batteries have a capacity of 1,500 to 2,100 mAh while tablet batteries are in the 6,000 to 11,000 mAh range.

If all you want is a quick charge to give you a couple of hours until you can get to a wall socket, go with something small, inexpensive and lightweight like the 1,800 mAh Triple C Power Mate Plus ($29), which plugs directly into an iPhone 3GS, 4 or 4S.

The 2,200 mAh MiPow Power Tube ($39) is compatible with a wider range of mobile devices and will completely charge a smartphone. Encased in what looks like brushed aluminum, it weighs 70 grams and is the size of a cigarette lighter.

A larger footprint and more heft will provide even more charging capacity. Take the HyperJuice Mini ($100), which is about as big as a smartphone but thicker, weighs 238 grams and delivers 7,200 mAh. It also has the advantage of multiple charging ports so that two mobile devices can be charged at once as long as they are USB compatible.

For those who prefer not to juggle one more device, there are charging sleeves or jackets that snap onto the devices they already have. Mophie is the leading provider of iPhone charging cases with its popular Juice Pack Air ($80). It has a 1,500 mAh capacity and adds 70 grams to the weight of an iPhone 4 or 4S.

For Android users, there is PowerSkin, with 1,500 mAh charging cases for a variety of smartphones. They range in price from $40 to $80, with some selling for as little as $5 with shipping if the model has been discontinued.

If you want an iPad charging case, there is the KudoCase ($130), which relies partly on solar power. It converts outdoor and indoor light into energy for a continual trickle charge. Just know that six hours of sunlight offers only about an hour of iPad time, so you will still need to recharge the case occasionally by plugging it into an outlet.

The Powermonkey Extreme ($200) also has a solar component with a separate solar panel for recharging off the grid. Marketed to rugged outdoorsy types, the 9,000 mAh Powermonkey weighs 240 grams without the solar panel. It is compatible with most mobile devices, including handheld GPS systems; is shockresistant; and, if submerged, is waterproof up to 30 minutes.