Nokia: Lumia 800 has battery issues, a fix coming in January
Despite Nokia promised two battery-related updates almost a month ago, it is just now we get official acknowledgement about the Lumia 800 battery issues.
Nokia's own investigation reveals a software bug which is "limiting the phones ability to access the full battery capacity". According to Nokia, not all Lumia 800 phones are affected by this issue.
There is very easy way to check your unit. First, fully charge your battery and then dial ##634# to access the Service menu. Go to Battery Status section - if your capacity is less than 1000mAh then your Lumia 800 is indeed having a problem accessing the full battery capacity.
Dont worry though - the fix is on the way and the critical update should roll out early next year. If you dont want to wait though, Nokia will replace your phone.
Oh, there is one more thing worth mentioning - the Lumia 710 is not affected by this issue.