[halB]

If I remember correctly the external power supply they used was a battery charger. They used that because they had to disconnect the battery for safety reasons, but they want some of the electricals (such as radio) to function. As for disabling some of the functions I am not sure how they did it - may be they just pulled some fuses. None of that could have cause any issue with the car's electrical system.

As for the cigarette lighter it is possible that showgoers might have been poking at the empty socket and caused the damage (the lighter itself would have been removed before the show). Did they replace it the last time or did they just "fixed" it by whatever means?

Back to the belt: A serpentine belt should last 100,000km. If it breaks like that there gotta be:

1) A defect
2) Something else causes it - such as a cracked or binding pulley, or something else had weaken, nicked, or rubbed against the belt.