Some Nokia Lumia 800 devices have a little problem with the battery’s capacity. The Lumia 800 has a 1450mAh capacity, but some Lumia 800s are only using 1300mAh, or even less than that. This results in a ridiculously short battery life. Here’s how to know if you have one of those problematic Lumia 800s:
1. Do this while the phone is fully charged. (Just unplugged)
2. Go to “Phone” and type ##634#
3. Hit accept and scoll down to Battery Status
4. You current capacity should be close to your Full Charge Capacity
Nokia has promised to update the Lumia 800 software early 2012 to solve this issue, however, you have the right to exchange your Nokia Lumia 800 right away for a replacement if this issue bothers you. Just contact your country’s Nokia Care customer service. http://nokia.com/support
My Lumia 800 seems to be one of those, the current capacity and full charge capacity don’t match.