You mention that battery was dead after a warm engine had been left to cool for about an hour whilst in church. (Assuming that you are saying the battery is dead by symptoms rather than tested at this moment in time) then this reminds me of a problem we had with a car where it would perform normally but battery would appear to die occasionally. This narrowed down to it appeared to die if you tried to restart when the engine was around the same temperature ie. not cold, but not up to running temperature. The actual fault (apparently quite common on this non Mercedes car) was caused by the battery positive lead fragmenting inside the insulation caused in this case by the lead running close to the exhaust where the consent hot and cold had caused metal fatigue in the lead. When cold the insulation held the core tight enough for a good connection, when hot the core had expanded enough for a good connection, at a temperature in-between then the fragmented core become high resistance when trying to draw a high current. Just about impossible to find as a fault by testing. Might be worth changing some of the big leads that may look and test perfectly OK when tested, but might be routed such that they may suffer from fatigue caused by heat or physical vibration...