[Biker1]

Good observation regarding the cover as being the source and not the battery itself.
I checked my other 2 batteries before and noticed the same substance.
But strange as it happens after only a short while.
Something can be leeching from the cover due to the heat of the battery.
If you touch the battery while the Diamond is in use, you will notice that the area of the battery that is showing the substance is the warmest part of the battery.
The areas around that area are cooler.