Power issues
BOAC,
The power supply issues are one of two things: the batteries are going bad, have gone bad, or have become defective.
But it also might be the motherboard battery. (Something many users overlook during troubleshooting.) I don't know how old the system is
but the motherboard battery doesn't usually last all that long. Replace the motherboard battery and if that solves the power issue that was the cause. If not, then the battery pack needs to be replaced. (which is easy enough to do.)