by It takes a lot of power to light up an iPad’s 9.7-inch screen—and even more to power the fourth-generation model’s Retina display. That’s why the device is packed full of battery capacity—an impressive 11,560 milliampere hours’ worth for the latest model. But although our battery tests have shown that, under heavy use, the fourth-generation iPad can last for more than 9 hours on a single charge, sometimes you need even more juice.
Whether you’re exploring the great outdoors or enduring a power outage, a portable charging device—that is, a big battery—can come in handy when electrical outlets are either unavailable or, as is often the case, not functioning. Portable batteries can also charge your smartphones, media players, and other mobile gear that charge over USB.
We recently put nine such devices through their paces and found that while all could help in a pinch, only one could provide a full recharge of a fourth-generation iPad.
What to look for
You should keep an eye out for several things when you’re shopping for a portable charging device, including capacity, convenience, and cost. If you’re seeking a portable charger that offers the greatest amount of juice for your iPhone, iPad, or other USB-charged device, look first at battery capacity, measured in milliampere-hours. The batteries we tested range from 6000 mAh to 16,000 mAh.
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