First time I have had this, and not too sure of the reason. I turned on my controller and it made a steady regular beeping noise, this continued even after turning on the P4, eventually I got a cold battery warning. After a few minutes and a complete restart the beeping stopped, and the cold battery warning stopped. I had stored the backpack in a cold car overnight. The beeping was even before I turned on the P4,is this a low temp warning for the controller?I have not read this in the manual. Any suggestions? After warming up I had a perfectly normal flight, hitting 30% battery after 21 mins.