Suddenly shuts off, turns on (completely reboots)

Question

Hi,
I have a Macbook Pro (15-inch, early 2011).  My computer suddenly shuts off (fully charged, plugged in, no warnings of low battery or anything).  When I turn it back on, it reboots completely (as opposed to restoring my session like it usually does if the battery dies) and says the battery is at 0%.  This has happened a few times now.  Does anybody know what it is or how to fix it?  Thanks in advance!
Some info:
Macbook Pro 15-inch, early 2011
OS X 10.9.5 (13F34)
Power info:
Battery Information:
  Model Information:
  Serial Number: D861125038QDGDLAK
  Manufacturer: SMP
  Device Name: bq20z451
  Pack Lot Code: 0
  PCB Lot Code: 0
  Firmware Version: 406
  Hardware Revision: 2
  Cell Revision: 158
  Charge Information:
  Charge Remaining (mAh): 365
  Fully Charged: No
  Charging: Yes
  Full Charge Capacity (mAh): 6026
  Health Information:
  Cycle Count: 428
  Condition: Normal
  Battery Installed: Yes
  Amperage (mA): 3918
  Voltage (mV): 11634
System Power Settings:
  AC Power:
  System Sleep Timer (Minutes): 30
  Disk Sleep Timer (Minutes): 0
  Display Sleep Timer (Minutes): 15
  Wake on AC Change: No
  Wake on Clamshell Open: Yes
  Wake on LAN: Yes
  Current Power Source: Yes
  Display Sleep Uses Dim: Yes
  GPUSwitch: 2
  PrioritizeNetworkReachabilityOverSleep: 0
  Standby Delay: 4200
  Standby Enabled: 0
  Battery Power:
  System Sleep Timer (Minutes): 10
  Disk Sleep Timer (Minutes): 10
  Display Sleep Timer (Minutes): 5
  Wake on AC Change: No
  Wake on Clamshell Open: Yes
  Display Sleep Uses Dim: Yes
  GPUSwitch: 2
  Reduce Brightness: Yes
  Standby Delay: 4200
  Standby Enabled: 0
Hardware Configuration:
  UPS Installed: No
AC Charger Information:
  Connected: Yes
  ID: 0x0100
  Wattage (W): 85
  Revision: 0x0000
  Family: 0x0085
  Serial Number: 0x00064712
  Charging: Yes
Power On Self-Test:
  Last Run: 2/24/15, 1:41 PM
  Result: Passed

Answer 1

Have you tried a SMC reset?
http://support.apple.com/en-us/HT201295
Ciao.