This thread is to discuss Android Battery Usage.
Please post how you use your phone, what model it is etc and any applications that run in the background.
I have a Samsung Galaxy S with Froyo BUJP8 Doc_Kalpik Rom and the K9 256hz Speedmod kernel. I am using the EXT4 lagfix for all partitions.
I am using JuiceDefender to turn on 3g/Wifi for 2 minutes every 30 minutes to conserve power, it also disables 3g/wifi and autosync from 12am-7am. I have autosync and background data transfer enabled at all times. I also have my brightness turned to 0% for 90% of the time, manually changing it when viewing outdoors. Tweetdeck is set to update once per hour, weather widget once per 8 hours and Friends widget (launcherpro) every hour.
Typically I charge overnight and take my phone off the charger at 7am. I usually read some RSS feeds/Twitter in the morning for maybe 10 minutes. I then listen to music/podcasts for 35 minutes driving to work. My typical usage during the day is light checking of twitter/facebook/sms/email throughout the day with ebook reading during all breaks. I then listen to music/podcasts for another 35 minutes on the drive home. Usually by the time I get home my battery is between 15-30% depending on whether I did any browsing on my phone.
Usually by the time my battery reaches 15% I have roughly 2.5 hours of screen on time. I have never had more than 3 hours of the screen being on before my battery dropped to 15%
I do have 2 spare batteries that are not of the same quality as the oem one, they usually only get 2 hours of screen on time. I charge my batteries using a wall charger a majority of the time.