Answer:
Ablation.
Explanation:
'Ablation' in general is demonstrated as the process of taking away or removal of a specific material out of an object through varied kinds of erosive processes like chipping or vaporization.
As per the given description, the research done by the visitor would be most closely associated to 'ablation' methodology as he attempts to destruct/remove the battery(endothermic material) from the car(object) that leads to him finding out that 'car won't start anymore along with dysfunctioning of lights as well as stereo' as the 'energy of the car in the form of battery has been absorbed'. Therefore, this research is most closely related to the 'ablation' method.