Battery drain with Unregistered device SE?

I have always had this 'unknown' device.  My assumption is that it is the Tegra graphics device, because it is missing in your (my) report and it appears in other people's reports.  See http://answers.microsoft.com/en-us/surface/forum/surf2-surfhardware/noticing-faster-battery-drain-after-february/9197b834-5259-4337-89a0-4b31ce95d960 for example.

As to why it is missing and showing as unknown?  My opinion is it's because the device is in some way faulty and is the reason for display errors that occur (SoD, battery drain ...).  However, I don't think it is now causing battery issues for me any more.  I'm getting 1% in 3hrs during connected standby. 

View your Reliability History and see if there is a Video hardware failure at some point in the past.  I was getting dozens (and dozens) of display errors in the log, which seemed to be waking the S2 all the time.  Check logs.  Now have a replacement - very few display errors now, but still HW error - see below - and the Unregistered device.

Have you a type cover?  That is causing issues for some?

I uninstalled KB2883200 last month and it 'seemed to make a big difference to battery life.  Try it. 

See WPC forum - http://forums.wpcentral.com/microsoft-surface-2/268732-3.htm#post2432297

This update is replaced by later 'roll-ups', such as April's big update, so you're safe.

See before and after -

I've checked my reliability history and I have only one noticible hardware error but none recently. In the case of the rollback of KB2883200 I did uninstall that update a while back and reinstalled the subsequent update. I haven't noticed any dramatic changes in battery life since.

Seeing as thou this issue seems widespread I'm hoping it's something that can be changed in a future update?

I forgot to mention that I do have a type cover 2 attached 99% of the time. I read issues regarding the type cover waking the device in standby by some have found that avoiding pressing the power button and closing with the type cover corrects this problem. I'm experimenting with that now.

Strange that you also get a HW error so early in the life of the device - or following a refresh.  I do believe there is some inherent issue with the display hardware.  Check the Event Viewer/Custom Views/Admin Events for display (4101) errors.  My previous S2 was spewing out these and was a cause of battery drain.

I also have a desktop and touch-screen laptop running W8.1-update and neither of them have such poor reliability record or error log entries.  Many apps, and maybe drivers too, really seem to have big problems with connected standby.  Needs to be sorted.

Yup just like you said I have a bunch of 4101 "warnings" not errors. I'm not sure if that makes a difference. It hasn't happened in the last few days thou. Does this mean I need to get a replacement sense its a hardware issue?