I had a similar problem with a car, it turned out to be a bad battery cable--it was corroded internally and would get hot at the bad spot when used due to the added resistance from the corrosion.
You might want to check the cables; the bad spot may feel stiff or brittle when you flex it.
That is an excellent suggestion, not to mention a relatively inexpensive item to take on next. Thanks for the idea_.very helpful !
