Now, before you run bq27200.sh script, go to /usr/sbin/

# cd /usr/sbin/
# bq27200.sh

Run those two command lines when your battery is fully loaded and you detach it from the charger.

Use your phone normally until battery starts to get almost empty.
Then run following commands again in xterminal window and leave it running.
# cd /usr/sbin
# bq27200.sh 10

Use your phone normally until battery goes fully empty and the device shuts down. You can connect the charger after the phone has shut down.

Now when you boot your device back up, you can see the true measured capacity of your battery by running:
# cd /usr/sbin/
# bq27200.sh

(One reason why it is this "complicated" is because bq27200.sh script has a bug; hardcoding i2cget path.)