I will be taking a train from Beijing to Guangzhou and it will be long trip with nothing to do so I'm hoping to play my DS and some ROMS on my laptop, the problem is battery life. So, I want to know if there is any kind of external battery that I can use? Any thing I can do with an electric scooter batter or back up power UPS type solution to power either of these two devices for 15-20 hours. I know there has to be something like this, I don't care about weight. Just not sure what to call it to make a search.