XPS 13 9360, low performance on battery with SpeedStep enabled

My dell xps 13 9360 with an i7 8550u gets about half the performance it should be getting when on battery power. However, it performs within expectations when the power adapter is plugged in. If I open a Cpu frequency monitor while running something intensive such as encoding video, I see that the cpu spikes up to 3.1ghz for an instant then falls to about 800mhz and stays there for a while before spiking back up to 3.1ghz and repeating the cycle. This is all happening while the cpu temperature is around 60 degrees Celcius so it can't be thermal throttling. I did find a stopgap solution for this issue however, if I disable Intel SpeedStep in the bios, I the expected performance on battery without any throttling to 800mhz. The reason its a stopgap solution is that the cpu frequency doesn't go down when the computer is idle and thus lowers battery life. I assume this is a software issue that can be fixed with a bios update but I might be wrong. Does anyone have a solution for this that doesn't involve reducing battery life?