Sudden Shutdown

I am aware of the similar thread about Macbook shutting down at 20% battery but I'm not sure if this is the same case.

This is the first time I've used the battery to below 50%. However, when I did use it today, my Macbook just suddenly shuts down at 20 minutes left. No warnings at all.

Is this normal? I thought it wouldve gone into sleep mode.

Thanks for any help (new Mac user!)

Your computer should not be doing that, and it sounds like the same problem I had. Whats the battery's charge capacity as seen in the "About This Mac->More Info...->Power" section?

Full Charge Capacity is 4857 mAh (97%).