If Primary (internal) Battery (601) appears in the alert message, it means the measured storage capacity of the primary (internal) battery is less than 25% of the original storage capacity. The number “601” denotes the associated error code that is recorded in the system log.
In order to try and resolve this issue, I'd suggest you perform a battery test and calibrate the battery.
Follow these steps to perform a battery test -
1) Shutdown the computer.
2) Turn the computer back on again and repeatedly tap on the ESC until a Startup menu appears.
3) Press F2 once.
4) Go to Component test.
5) From the list, run the battery test.