I have two strange behaviors.
I'm running a CPU and GPU intensive robotics task on my notebook on battery. Sometimes the battery lasts for more than 30 minutes, but sometimes the battery level suddenly drops to critical level after one ore two minutes and the notebook shuts down. In this case the notebook won't start without power supply, but when restarted it says 80% or more battery.
Sometimes the performance of my notebook drops dramatically. This may happen with and without power supply. The strange thing is that after pluging in and out the power supply the performance is back to normal.
I'm not sure if these problems are connected and if they are operating system problems, BIOS problems or hardware problems.
I'm running Xubuntu 16.04 on a Clevo W650SR notebook.