How to know the duration of battery usage in one session?

I would like to know how long was my battery running since it's last charge. There is a built-in time-remaining counter but I would like a time-used counter.

Solution 1:

Starting with Mavericks (OS X 10.9), this is available in Activity Monitor. Open Activity Monitor from the /Applications/Utilities folder, and go to the Energy tab. The center pane of the statistics at the bottom of the window includes the amount of time since you last unplugged the charger, which appears shortly after you switch to battery power.

Solution 2:

You can try using the app Battery Truth on the Mac App Store. It costs $2.99 CAD and is supports English and Russian. Though it won't work if you Mac OS is older than 10.10.

The app will tell you:

1. How much longer the battery will last
2. What time the current charge will last you until
3. How long the battery will last on a full battery
4. How long the computer has been running on battery power for
5. And during that time how much of it the computer was asleep or running