For what it is worth, my understanding tallies with Wayne's description. Essentially, deep discharge cycles tend to create compounds which do not break apart and add internal resistance to the battery. This is what lowers energy density. Keeping the ions separated as much as possible (battery fully charged) slows the process enormously -- though age will still cause a slow accumulation of such compounds. Once those are at a sufficient level, regardless of memory effect, your battery becomes effectively useless because its internal chemistry is "clogged." If the BCM is out of whack and not correctly determining how much charge is remaining, or how to effectively condition the battery, this might explain the "runaway" behavior we are seeing? With several hours of travel time on the highway coming up, if I see such an event I'll have the time to see if it will eventually recover, then act normally. The inconsistency is what makes me suspect the electronic components -- though battery aging could easily be a factor.