One time, after getting one of my batteries in place, the left side did not lock in completely. Which got me in the habit of placing my thumbs on the battery right over the locks and pressing evenly until I hear it click into place. Then checking to make sure both side are locked... and do not lift even a little bit off the Mavic body. This has worked out fantastic for my peace of mind before lift off. Well....
The other day, after going through all this, as I was placing my Lil' Dragon onto the launch pad, I 'felt' one side of the battery release. This brought to my attention how I was holding the MP when transporting to the launch pad. I didn't grab the release tab directly. The inner side of my thumb, while gripping the Mavic, put just enough pressure onto that tab to let it loose from it's lock! Glad I caught it before take off... I tend to re-check the battery locks (like I mentioned above) just before powering on now.
Just want to put this out here. Be mindful about how you're gripping your MP after your pre-flight check and moving it to the take off position. It very well my save you from a loss of power and dropping like a brick.