Tom, It's unsettling (and a little scary) to see those pics of the smoking battery. I'm not surprised that the logs don't show anything strange because the controller board inside of the battery would have prevented this type of event from happening if it was caused by a short in the battery or quad. I have seen issues similar to this with very new batteries or very old batteries and it always comes down to physical damage to the cells. With the very new ones it's usually a manufacturing (or assembly) defect that has compromised the shielding of the internal LiPo cells. With the older ones (over a few hundred charges) its either a change in the chemistry of the cells (that normally shows up during use like yours) or a defect in the shielding that eventually wore through because of extensive use or a rough landing. You would certainly have a case with DJI for replacement if the cell was new but it might be a little harder if it was a very old cell. Even though this can be a devastating experience while flying, just be thankful it didn't happen while you were charging the cell in your home. This is exactly why I recommend using a LiPo safety bag for charging and transporting the cells. If you can let me know a little more about the age and condition of the cells, I can narrow it down a little more for you. Here's a clip I did on the LiPo Safety Bags a while back and you can find these at a variety of websites -