Help HTC Desire Battery Problems

My battery on my HTC Desire HD used to last a whole day and night, but i got a software update for my phone about a month ago and since then i have noticed my battery only lasting about 11 hours untill its on red.
I went camping for two days, before i left i fully charged my phone, and so did my cousin who has a iphone, my battery died by night time, but my cousins lasted 2 days with his mobile net always on. I dont understand =(
It was only since this update, also is there any other battery i can buy for it? I saw some gold ones on ebay that says they are twice as good, but i dont know if they are really safe.



El Presidente

Beware The Milky Pirate!
Some apps didn't like the gingerbread update, Green Power was one of them, it caused massive battery drain. You don't have that installed per chance do you?

Failing that, look at your battery stats in Settings -> About Phone -> Battery -> Battery Use. What apps are listed? If you click the graph at the top of the screen, do the bars underneath "screen on" & "awake" differ much?