If you open the Crosh shell (Ctrl+Alt+T) I believe there is a command to test the battery's ability to hold a charge if you run `help_advanced` and look through the commands there.
Also keep in mind the screen brightness and the number of open tabs and the number of extensions you have running in the background can greatly affect your battery life.
I would run the above test once as your user, and then power off the Chromebook complete and boot fresh and rather than logging in again choose the "Guest" session, then use the same command you used in the Crosh shell and see whether the discharge rate is different.
You should also try running as Guest for a day or two and see if there is a large difference in battery life if you aren't logged in as your user with all your extensions/tabs/etc.
Let us know what the results are and we can give you more advice based on that information.