Help: when unplug xps l502x, the screen become darker.

I just bought Dell xps L502x today. I notice that if I unplug the power the screen will go darker. Is this a problem or normal?

Then what I should do if I want to use battery (without plugging the power supply) because the screen will go darker. not light enough as when I plug it. This happened to my Acer laptop before and I hate it because I thought my acer must have a problem because it's old.

Please help. Thank you.

 

You can simply turn up the brightness...The Auto-dimming is a battery saving feature. function key plus f7? or f8? not sure, using my work lappy right now.

 

Please let me know if this is normal or not.

Also I just went to battery option and set it as high performance and the light is up again. So I assume this is normal because the system want to save power when it's not plugged?

Another question. When I unplug it, the battery shows 2hours left and it decrease quite quick just open a few webpage and listen to the song. This laptop has 9cell batteries. I heard it can last more than 6 hours but why is it showing only 2 hours left?

By the way, I haven't plugged the power supply for long because I want to try the batter and it was showing 100% battery when I turn it on. Should I charge battery first or what should I do?

 

Yes, it's normal.

The Windows battery indicator is woefully inaccurate/inconsistent when it comes to time remaining. My brand new 15z goes from 7 hours left, to 5, to 3, then back up to 7, in the space of 10 minutes.

 

It's not that it's inaccurate exactly, it just doesn't average over a long enough period to account for the rapid change of power draw with SpeedStep and TurboBoost.