I love Battle for Wesnoth. Not only is it a great game with hundreds of hours of content, but it's also easy on the battery. What are some other quality games that play well during long commutes?
The Quest is enormous and not too bad on battery consumption. PathPix and ColorCross are also pretty great if you enjoy puzzle games. EDIT: Oh, and Sword of Fargoal. Lots of fun, low battery consumption. Randomly generated dungeons mean it doesn't get old. Rogue Touch is probably similar in this regard, but I haven't played it.
First of all, Battle for Wesnoth is probably my favorite game, it's mind-blowing. So yeah, Rogue Touch and Fargoal are awesome. Another game with a ton of Content is Necromancer Rising, which I personally love. PuzzleQuest will also keep you busy for a long long time, and it's a great mix of casual and RPG. Finally, if you haven't checked out Warp Gate yet, then you should. It's deep as hell and gorgeous to look at, although I don't know how it does on battery...probably not so well. These are probably my 6 favorite games at the moment, and all of them will provide many long play sessions for a long long time.
Yeah, I thought about putting Puzzle Quest on the list, as it has a ton of gameplay, but in my experience it chews through a surprising amount of battery. I imagine Warpgate and Necromancer Rising both do as well, being fully 3D games. Oooh, Gamebook Adventures: An Assassin in Orlandes. It may not be as huge as some of the other games mentioned, but it'll give you at least a solid 4-5 hours of reading, more if you go back for additional endings, and it's really light on battery use.
Space Miner: takes around 4 hours for a playthrough (that's just to beat it, a lot more to beat every system), great on battery, and is incredible