My macbook pro (late 2008) shuts down but battery is at 25-30%

Question

My macbook pro (late 2008) shuts down but battery is at 25-30% and I don't get a low power warning box before this happens.  This only happens when the power chord is not connected, and it restarts with no problems once I put the power chord in. Does this mean I need a new battery, or is it an indication of something else? Using osx 10.5.8

Answer 1

Mine is Unibody 15" MBP late 2008, with the exact problem as yours. It can be a sudden shut down at 25-32%, or, after upgrading to OS 10.7.2, can be hang all of sudden on battery power.
Condition on, "Replace Soon". From 4.5 - 6 hours when new, goes down to 1 - 2 hours on discrete graphics.
But after 'abusing' it for the first year in the heat of Jakarta's climate in a non AC room when doing a video editing, before moving back to a comfort AC room at home sweet home, the battery performance is still top notch comparing to other kind than Apple. Also, it caused me to replace the right fan, after a lot of hard work on that first year. Oh, and by the way, I regularly done the battery calibration, at least once or twice between 3-6 months.
Here's also an useful link about battery I found on the internet:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batterie s
My battery condition:
Battery Information:
  Model Information:
  Serial Number:          6N8389BD13EB
  Manufacturer:          SMP
  Device Name:          bq20z951
  Pack Lot Code:          0
  PCB Lot Code:          0
  Firmware Version:          002a
  Hardware Revision:          000a
  Cell Revision:          100
  Charge Information:
  Charge Remaining (mAh):          2192
  Fully Charged:          No
  Charging:          Yes
  Full Charge Capacity (mAh):          2716
  Health Information:
  Cycle Count:          616
  Condition:          Replace Soon
  Battery Installed:          Yes
  Amperage (mA):          254
  Voltage (mV):          12392
System Power Settings:
  AC Power:
  System Sleep Timer (Minutes):          0
  Disk Sleep Timer (Minutes):          10
  Display Sleep Timer (Minutes):          15
  Automatic Restart on Power Loss:          No
  Wake on AC Change:          No
  Wake on Clamshell Open:          Yes
  Wake on LAN:          No
  Current Power Source:          Yes
  Display Sleep Uses Dim:          Yes
  GPUSwitch:          2
  PrioritizeNetworkReachabilityOverSleep:          0
  RestartAfterKernelPanic:          157680000
  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
  RestartAfterKernelPanic:          157680000
Hardware Configuration:
  UPS Installed:          No
AC Charger Information:
  Connected:          Yes
  ID:          0x0100
  Wattage (W):          85
  Revision:          0x0000
  Family:          0x00ba
  Serial Number:          0x0063ac36
  Charging:          Yes
Got the battery replacement today. Hopefully it will last for at least 3 years like it predecessor.