I really like the LIion batteries from Electrovaya. I have tried both with my fujitsu lifebook. Here is my comparison.
PRICE: N-charge 200$ Best Buy
PowerPad120 180$ Ebay (shipped)
RUN TIME: N-charge ~3hours
(lid open) PowerPad120 at least 6 hours.......... indicator showed 2 green lights out of 5 total lights.
Charging: N-charge wallwart charger, charges quick, but didn't time this
PowerPad120 plugs into your lap top a/c cable, charge overnight
So the PowerPad 120/160 out performs the N-charge batts from in a major way. It will run a whole show with the power showing 2 yellow lights easy with the lid open here and there to set/check levels. If you want to run at festivals this is the battery to get. The 160 will run at least 10 hours with the lid open according to a friend that has one. Look on Ebay...these babies are 250-400$ new. Also check
www.electrovaya.com for a chart that will tell you which model (A B C D) you need with your lappy.