You can get an external battery pack for long trips.
http://www.amazon.com/s/ref=nb_sb_no...y+pack&x=0&y=0
We use one for our portable DVD player to amuse my grandson on long trips and it works great. Most of the time it sits in a drawer, but we do use it a few times a year and those times make it well worth the price and trouble to carry an extra device.