I am starting to get the same thing.
The battery will go from 38-43% down to 18-23% in an instant. This is just using a widget from the homescreen though (I think it's GSam).
Anyways, I'm going to try some battery meter re-calibrating over the next few days. I need all the battery I can get. It has never worked properly in my mind. I used to keep it on airplane mode all day since the building I worked in had no signal anyways, so for 7-10 hours a day it was on airplane, screen off, wifi/gps/bluetoof off, everything. Still wouldn't last a full day. Now it's even worse.