Originally Posted by mark manning
Not gonna lie that's one of the weirder things I have heard. I'm not sure what would cause that. Since you are stock you may want to consider downloading the factory image and reflashing it. If that still doesn't help then you should call Google.
Wish I had a better answer for you. Maybe someone else knows something I don't.
Sent from my Nexus⁴
To re-flash the factory image do I need to root my phone?
I had experience something a bit similar but on my iPod touch each time I reboot it the battery dropped 3-4%, but I had never experience a random reboot that made my battery drop from 48-50% to 15%, hopefully this will be the only time that this will happen, if this happens again I guess I will contact google.
Oh and I also forgot one detail I don't know if is relevant but the reboot happened when I was reading the news on google currents.
I will attach a couple of pictures where is more clear to see the drop, if some has an idea of why this happened please post