Energizer Energi-to-Go XP18000 battery pack
Also sold under the XPal brand, the monster Energizer Energi-to-Go XP18000 lithium-ion battery pack is the maximum size TSA will allow in your carry-on. It's the only battery system I know that gives you a huge collection of battery tips and two more free tips per year for life. With three voltages (9-12V, 16-20V, and 5V USB), this system will charge or at least run most laptops, cameras, and travel accessories. Since Apple is finicky about the MagSafe adapter, you need to purchase the car/airline adapter from Apple, then use XPal's 12V cigarette adapter. As a thumbnail, I've run my CradlePoint CTR35 WiMax Router off the USB port for 10 hours and still had a little life left in the XP18000.