Hi
So your answer (Dells) is to dim your screen so you cannot see anything and wind the power down as well lol....
When people come into my computer shops to buy Lappies (including Dells) we say to them ...regarding battery time....take the manufacturers figures with a LARGE dose of salt....which means....divide the figure by three and you will be a lot closer to full power battery time...
We sell a LOT of laptops and repair them as well, and every time I see an advert on the TV which says something like....6 to 8 hours battery life, I laugh....
I fail to understand why manufacturers like DELL continue to exaggerate their claims...
All the best Brett