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 phone’s 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.
Don’t worry though - the fix is on the way and the critical update should roll out early next year. If you don’t 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.
worst battery i have seen in lumia 800
i have facing battery problem in my nokia lumia 800. on standby mode its run only 8 hours after 100% charged.i have facing this problem since 3-4 days only but before it run maximun minimum 34-35 hr.after 100% charge.
I don't think Lumia 800 battery is really that problematic.. am using it since 1 month.. I found batter is perfectly fine for such big screen.. am charging daily once overnight. I use more than 2 hours a day for incoming/outgoing. Frequently checking...