Nokia Lumia 800 users are facing the same famous problem as the users of iPhone 4S faced i.e. battery problem, which is poor as compared to other Nokia Phones.
Nokia Lumia 800 has 1450mAh battery but even then the problem is there. Perhaps Nokia didn’t used the full potential of that battery.
It looks like that Nokia is working on the battery issue as two updates by Nokia are planned to improve the battery life. Reports said that they will enable the updates in January of next year.
Nokia support discussions showed,
We understand that some people have expressed concerns about battery life on the Nokia Lumia 800. Early investigations show that most people are enjoying the full Nokia Lumia experience without any problems and we have not been able to identify a single root cause that would lead to erratic battery behavior at this stage. A software update in early December will make some improvements to power efficiency, while a second update in early January introduces high voltage charging, increasing the Nokia Lumia 800’s battery power from 1300mAh to 1450mAh. These are scheduled improvements and will enhance the overall experience, but are not designed to address any issues that may be occurring with individual products. We recommend that anyone who has concerns contact local Nokia care representatives at their earliest convenience.