Macbook Pro shuts down at 30% battery
The first thing I'd recommend you try is resetting your MBP's System Management Controller (SMC).

Resetting the SMC

To reset the SMC on your particular MBP follow these steps:


Shut down your MBP
Unplug the power cable from your Mac
For 10 seconds, press and hold at the same time the shiftcontroloption keys (on the left side of the built-in keyboard) and the power button
After 10 seconds let go of all keys and the power button 
Plug in the power cable
Turn your MBP back on with the power button


Once you've done this I'd fully charge your MBP and then test to see if the same behaviour returns.