http://www.macnn.com/articles/08/11/11/quickertek.macbook.battery/
QuickerTek unveils MacBook external 8-12 hr battery
updated 07:45 pm EST, Tue November 11, 2008
QuickerTek MacBook battery
QuickerTek has unveiled its latest Mac laptop accessory, an external battery for 15-inch and 17-inch MacBooks that is claimed to extend the power life by 8-12 hours. The device uses a standard MagSafe connector which charges the notebook battery before taking power from the external source. The Li-ion polymer cells are enclosed in a housing that measures nine by six inches, with a thickness of one inch, and weighs approximately five pounds.
The included AC wall adapter is claimed to reduce the MacBook battery charging time down to three hours, with an LED charging indicator provided to check the status.
The MacBook External Battery and/or Charger is available from QuickerTek for $450, and comes with a one-year warranty.
Fresh-Faced Recruit
Joined: Aug 2007
Expensive
At $450 I think I'd prefer to buy a gas generator, even at the expense of the noise and extra weight.