Recently had a client with an old Fordson tractor that killed its battery shortly after shut off.
Problem was that the generator relay was faulty and would try to motorize the generator when the key was off.
Always look for zebras.
Reading this thread and this was my first thought. With the advent of alternators and integrated regulators we've forgotten how finicky some regulators could get. A little too much moisture, a loose ground, corroded contact points, or a spring that is losing tension - all can contribute to a charging system that becomes unreliable.
As much as I agree with the idea of installing a quick disconnect switch (I have one on my truck) getting to the heart of the matter makes better sense, especially when you find yourself a couple of hundred miles from home.
