I am trying to extend battery operating time on an ARM laptop running Ubuntu 14.04. All I need is a terminal with word processor runnning in it. Nothing else needs to run. So, my question is: Which services, drivers, modules can I kill/unload to get the best battery life with only terminal functions remaining and what's the best way to accomplish that or automate that?
Getting rid of drivers or modules won't help you much and I doubt that unnecessary services consumes noticable amount of battery life. But of course you might want to look for processes that consume CPU time using
glances. For I/O operations it's better to use
iotop. And for network connections you might want to look at
What you can do to really extend your battery life is to maintain it in proper way in the first place, but you can read about it elsewhere.
Then, if you need terminal with word processor - switch to lightweight window manager, i.e.
xfce. Or you can even go crazy and switch to
blackbox window manager.
Consider disabling services like cups if you don't use printers, bluez if you don't use bluetooth. If you're paranoid you might even switch to static IP configuration and disable DHCP.
I also recommend Stacer for cleaning stuff up, if you want something that works automagically.