On Mondays and Wednesdays, I've been having an interesting problem: two almost-adjacent two-hour classes that require me to run back to my dorm after the first class is over, so that I can recharge my laptop. Annoying? You bet.
I researched an extra battery but found out that one would run me $180, and I wouldn't be able to use my docking station with it. So I came up with this:
"This" being a 180-watt-hour battery pack constructed from two UPS batteries and a car adapter. Now I can run around for eleven hours without having to plug in - although my ability to run around is somewhat hindered by the fact that they weigh in at 5.2kg. Either way, better than spending $180.