title_body: Is there a way to estimate battery discharge duration from mAh and C-rating? Lots of batteries are out on the web, and I understand what the values mean. But I would like to get a battery with a good discharge duration, so is there a way to tell an approximate battery life based on mAh and C-rating?
upvoted_answer: The capacity and C-rating don't tell you how long the battery will last, just how quickly you could discharge it if you really wanted to do it as fast as possible.
  It's perhaps analogous to the top speed of a car - just because your car can reach 120mph doesn't mean that a journey of 120miles will take an hour. Most of the time you'll never reach that top speed.
  A high C rating is like having a really big fuel hose on a car. You might need it on a dragster but it won't make an ordinary car any faster, or use fuel any faster.