MacBook Suddenly Shutting Itself Down

Question

Twice so far today my Macbook has shut itself down. Both times it has been very quick in going to a blank screen. Both times there has been plenty charge in the battery but it hasn't been connected to the mains.
In order to restart it I have to connect it to a power supply.
Any ideas? Is it battery trouble?

Answer 1

Here is all the info from the power tab
Model Information:
Serial Number: DP-ASMB013-3505-2014
Manufacturer: DP
Device name: ASMB013
Pack Lot Code: 0001
PCB Lot Code: 0000
Firmware Version: 0102
Hardware Revision: 0300
Cell Revision: 0100
Charge Information:
Charge remaining (mAh): 2359
Fully charged: No
Charging: Yes
Full charge capacity (mAh): 2524
Health Information:
Cycle count: 398
Condition: Good
Battery Installed: Yes
Amperage (mA): 779
Voltage (mV): 12147
System Power Settings:
AC Power:
System Sleep Timer (Minutes): 180
Disk Sleep Timer (Minutes): 10
Display Sleep Timer (Minutes): 180
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): 180
Disk Sleep Timer (Minutes): 10
Display Sleep Timer (Minutes): 180
Wake On AC Change: No
Wake On Clamshell Open: Yes
Display Sleep Uses Dim: Yes
Reduce Brightness: Yes