My macbook pro shuts down unexpectedly when battery gets to 20% and is not plugged in

Question

Why does my macbook pro keep shutting down when it gets to 20% without warning?
here is my battery information:
Battery Information:
  Model Information:
  Serial Number:          SMP-ASMB014-3774-64a
  Manufacturer:          SMP
  Device name:          ASMB014
  Pack Lot Code:          0002
  PCB Lot Code:          0000
  Firmware Version:          0110
  Hardware Revision:          0500
  Cell Revision:          0102
  Charge Information:
  Charge remaining (mAh):          3395
  Fully charged:          No
  Charging:          No
  Full charge capacity (mAh):          3677
  Health Information:
  Cycle count:          1148
  Condition:          Fair
  Battery Installed:          Yes
  Amperage (mA):          385
  Voltage (mV):          12442
System Power Settings:
  AC Power:
  System Sleep Timer (Minutes):          10
  Disk Sleep Timer (Minutes):          10
  Display Sleep Timer (Minutes):          5
  Automatic Restart On Power Loss:          No
  Wake On AC Change:          No
  Wake On Clamshell Open:          Yes
  Wake On LAN:          Yes
  Display Sleep Uses Dim:          Yes
  Battery Power:
  System Sleep Timer (Minutes):          10
  Disk Sleep Timer (Minutes):          10
  Display Sleep Timer (Minutes):          2
  Wake On AC Change:          No
  Wake On Clamshell Open:          Yes
  Display Sleep Uses Dim:          Yes
  Reduce Brightness:          Yes
Hardware Configuration:
  UPS Installed:          No
AC Charger Information:
  Connected:          Yes
  Charging:          No
WHAT DOES IT ALL MEAN??

Answer 1

That many cycles is amazing service. A battery that consistently shuts down at about the same charge level percentage every time probably has a bad cell (that info came form an Apple technician) and needs to be replaced.
It's given you far longer service than many of us get, and may be a new record around here for cycle count!