Discovered this overnight. I charged my battery for the HMC 150 and put it into the camera and then put the camera away in its Pelican case. However I didn't realise the camera was switched on, so it powered up and stayed on all night. It was quite warm when I got it out to use, but it worked OK and didn't flatten the battery too much - a trap for young players. Obviously the auto-off didn't work given that the switch was on and then the battery was inserted.