Anybody know what Charging Mode "ALWAYS AC" actually does? Doesn't seem to be documented anywhere (though happy to be corrected on this). The pop-up help says only, "For users who primarily operate their system while plugged into an external power source."

I had a previous (non-Dell) laptop that in this mode would limit charging to 80% to preserve battery life and I would expect the Dell to do something similar, but there is no indication that it is doing so. Displayed charge is 100% and as far as I can see it hasn't recalibrated the scale so 100% = 80%. Again, happy to be told otherwise. So what is it doing? Does it even work?