Got in a hurry to ride the other day--unplugged my battery tender and forgot to secure cap on pigtail--after riding for few miles I stopped for quick lunch. Got back on and battery was dead as a hammer. Looked around and noticed pig tail from battery cap was off and resting on my starter housing. Hope battery is ok--less than year old.
Had one of those melt before. Long enough ago I don't remember why though. One alternative to avoid the problem in the future would e a hard mounted connector. Company called Powerlet makes a bunch of different kinds of brackets with power connectors. They use that nearly universal BMW type power connector. Then just get a little adaptor for the SAE plug on the batter tender to BMW (they have those too, and about everything else you can think of) and it's a simple, easier to use, can't-fall-and-melt type of connection.
The same connection gets used on mine for battery tender, heated clothes and even the occasional other plug in accessory. On the touring bikes an easy place to mount is to take out the clip that holds the cruise control cable up just behind the rear cylinder and drop a small screw or bolt through that hole. Use it to attach the bracket then restrap the cruise cable to the newly mounted bracket. Makes it in there something like this: