2009 MacBook dies at 80%

My 2009 MacBook has recently been dying at 80% charge, and I tried resetting the SMC, but nothing happened. I can't calibrate the battery because it won't go down to 0%, only 80%. Here's the information for the battery:

 

  Model Information:

  Serial Number:

  Manufacturer:          DP

  Device Name:          ASMB016

  Pack Lot Code:          2

  PCB Lot Code:          0

  Firmware Version:          110

  Hardware Revision:          500

  Cell Revision:          200

  Charge Information:

  Charge Remaining (mAh):          3568

  Fully Charged:          No

  Charging:          Yes

  Full Charge Capacity (mAh):          4356

  Health Information:

  Cycle Count:          72

  Condition:          Normal

  Battery Installed:          Yes

  Amperage (mA):          978

  Voltage (mV):          12235

 

It says the condition is normal, but earlier today I turned on my computer and it said service battery, but then I restarted my computer and it said normal again. Why? Does it need to be replaced? It only has 72 cycles.

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