i charge from wall only ..
lappy se it takes ages ...
I had the same problem the 1st 4 days...now my battery life has improved drastically...apparently the nokia lumia 920 has the litium ion batteries...what that means..is that the more u charge it the better it becomes...how it works is its not at the optimum level when u buy it cause its obvly new...after a few charges it calibrates itself accordingly and gives u the optimum usage value...this may take upto 10 ~ 20 charges...now with heavy usage i get around 5% ~ 7% batt burn an hour...so arnd roughly 12 ~ 15 hours of drainage time from 100 to 4 ~ 3.
This also depends on your bg activity like live tile updates, brightness, nfc, bt, pushin email updates, sensitivity, lock timer etc...yes i have noticed at times some unanswerable drains..but thats mostly cause of some apps not optimized for wp8 yet...future updates shld fix this...
For example :- I have my bt off sensitivity minimum, nfc off, wifi on, data if im goin out, email on hourly, xbox off, bg activity minimum like batt widget, cnn, weather, n lockscreen pic changer and another 2...roughly set on hourly or 3 hours...today i took it of charging at 6 in the morning..heavy use till 9 i.e 2 hours of music(stored not mixed radio)...whatsapp...update notifications and reading some cricket content also a few calls....went down 29% din use my phone much till 1ish battery was at 68% after that moderate use till 12 at night...by that whatsapp regularly...email checking...fooling arnd with camera..listenin to few songs..showin off my phone bla bla bla...basic stuff ..oh yea i spoke for 1hour 30 minutes in the middle...at arnd 12ish my batt was 9% (with 60% of it on wifi and the 40 on data plan)...which is satisfactory to me so..yea just hang in there it shld get better...i hav also had days in the start that it wont make it to 4~ 5 hrs..
Also i have noticed a significant drain when using the nokia music...mixe music option even after u are done and u shut the app and the song, u dont really shut the song..u pause it as in..u can press the volume rocker to the side of the phone and resume where u left off..havnt really found a way to stop the song completely but it disappears after arnd 12~15 minutes...another way i hav found to overcome this is startin and stoppin stored music...just saying during that time the battery just drains like a B*****e..apart from that there are sudden spikes but..it settles down so yea...
I have used a s2 and a sony xperia..on an average it use to last me arnd 6 ~ 8 hrs...data plan does drain ur battery..arnd 11% n hour...so this phone shld give u that much...if not more...I know it sucks that this phone has so many awesome features but u cant really enjoy them..cause of battery and other reasons...but the question is to be asked do u really need em??? until u really do...switch em off...