I will bring along my Nokia E61 on board for watching movies. I will tansfer the DVDs into the 3GP format and stored them in the mini-SD for later viewing. I intend to watch about 5 movies in near DVD quality. For 14 hours flight in business class of a 747-400, is it possible that I can recharge my cell phone battery using the in-seat power supply?

What kind of adoptor I need to buy in order to use the in-seat power supply?
Or I should just drop this crazy idea and buy a bunch of battery packs instead.