I have 2 Canon bodies that share the same batteries and another Canon body (converted to IR) that uses a different battery.   Should have had plenty of battery power to handle the day.  But I didn’t count on 32 – 37 degree F temperatures.   From the first shoot of the day I started to get the battery dead message.  Luckily I knew that I needed to take the “dead” batteries and put them in a warm place (inside pocket).  So that by the time the next battery appeared to be dead, I could re-use the last one.  I was able to make it through the day but it involved a game of musical batteries, swapping them out every 30 minutes or so.