In the days when I traveled a lot, I used IBM ThinkPad X laptops with expanded (9-cell) interchangeable batteries. You just take a spare charged battery and swa

In the days when I traveled a lot, I used IBM ThinkPad X laptops with expanded (9-cell) interchangeable batteries. You just take a spare charged battery and swap them over. I once did London -> Chicago -> Seattle and still had about an hour of battery life for the bus from seatac. That wasn't continuous use, but as much use as I needed.