Recently, my 2011 MacBook Pro 13' produces strange instantaneous jumps in battery percentage. Sometimes, when it is discharging, it drops by ~40% (and if it was near or at less then 40%, it shuts down unexpectedly), sometimes (both when discharging or charging) it suddenly increases by 40%.
The output of coconutBattery shows that the maximum charge is at the half of the design capacity when the 40% is "missing":
Then the maximum charge seems to go back to normal:
System Report says:
Battery Information: Model Information: Serial Number: W00030C0L77ZC Manufacturer: SMP Device Name: bq20z451 Pack Lot Code: 0 PCB Lot Code: 0 Firmware Version: 3 Hardware Revision: 2 Cell Revision: 100 Charge Information: Charge Remaining (mAh): 2979 Fully Charged: Yes Charging: No Full Charge Capacity (mAh): 2979 Health Information: Cycle Count: 86 Condition: Normal Battery Installed: Yes Amperage (mA): 0 Voltage (mV): 12471 System Power Settings: AC Power: System Sleep Timer (Minutes): 10 Disk Sleep Timer (Minutes): 10 Display Sleep Timer (Minutes): 180 Wake on AC Change: No Wake on Clamshell Open: Yes Wake on LAN: Yes Current Power Source: Yes Display Sleep Uses Dim: Yes PrioritizeNetworkReachabilityOverSleep: 0 Standby Delay: 4200 Standby Enabled: 0 Battery Power: System Sleep Timer (Minutes): 10 Disk Sleep Timer (Minutes): 10 Display Sleep Timer (Minutes): 15 Wake on AC Change: No Wake on Clamshell Open: Yes Display Sleep Uses Dim: Yes Reduce Brightness: Yes Standby Delay: 4200 Standby Enabled: 0 Hardware Configuration: UPS Installed: No AC Charger Information: Connected: Yes ID: 0x0100 Wattage (W): 60 Revision: 0x0000 Family: 0x00ba Serial Number: 0x002b46f4 Charging: No
Should I suspect hardware failure, or is there something I might try to fix this erratic behavior?