New MacBook Pro Retina, bad battery?
Best is to use Apple tools already on your Mac to check your battery.

Open Activity in utility folder- and look under the the Energy tab.



Next, open About this Mac- More- sys report:

Look for battery information there.

It should show something like: 


Fully charged capacity (>6500 mah), --that is a good indicator how "old" is the battery, the older they get the lower is the Fully Charged capacity number.
Look at the charge cycles (&lt;5)- a good indicator how many times the battery was charged, with normal life been 1000 Cycles (or 3-5 years)