There's no shortage of mobile battery solutions for keeping whatever combination of smartphone/tablet/iPod/e-book reader you tote happily topped off when their juice levels get critical. Fewer are the options that have the fortitude to take on a laptop, though, which is why we're particularly in lust with the HyperJuice². It's available in four different capacities, but we tested out the 100Wh unit, which is compact and light enough to be comfortably mobile while still offering a staggering enough amount of stored power.
As is instantly apparent, HyperJuice²'s sleek modular aluminum design has Apple to thank for inspiration. Tucked inside are a 27000mAh lithium battery – which nicely is replaceable – and there are two 10W USB outlets that can charge two iPads or similar 4.5-amp devices simultaneously. Multiple USB ports are certainly useful, but our focus is on backup laptop power, and using an Apple MagSafe Airline Adaptor our MacBook's life gained an astonishing extra 25 hours. By any measure, that's a remarkable feat. (Note that the airline adaptor acts like AC power and doesn't charge the battery – for that you'll need to buy the separate Magic Box.) On our last overseas flight, we were also able to simultaneously charge our iPad, iPhone, and MacBook Pro (yep, we admit we're Apple fans) off of the HyperJuice² and arrived with batteries full and having finished our work.
Fully recharging the unit in a wall socket takes about four hours – a respectable trade-off for its heavy-duty output – though we noticed the OLED display only ever got to 98 percent, a factor we attribute to the inevitable but slow deterioration of battery life (the HyperJuice² is rated at 1,000 recharges). Battery performance also depends on environmental conditions – namely, temperature – which the OLED display shows in degrees Celsius. We also appreciated the "Remaining Time" readout for when the battery is discharging (which steadily declines when you have all three devices connected) or "Time Until Full" during recharging.
Now, 300 bucks is no small change for what is essentially a really big battery, but if uptime on your devices is mission critical, then the HyperJuice² is for you. We've seen nothing else that compares. [$300; hypershop.com]