Lid down isn't low power mode, if I'm not mistaken. It only switches off the LCD.I also seem to be having a problem with charging the battery, with the lid down in low power, it took me 5 hours or so to get from around 30 to 60-70 percent of battery; is this normal behavior? Btw, my battery was fully drained on arrival if that helps any.
To enter low power mode, you must slide the power switch to the right. The LCD will power off and a lot of other services are all switched off (like WiFi, bluetooth and so on).
Did you have better luck with your nubs? Take a look at the input tester.