pyrofuse 9j1915463A Battery CutOff Fuse Overload Protection Trip for Audi VW Porsche is a safety device in the main electrical system that protects the vehicles battery and wiring from severe overloads or short circuits. Its essentially a big fuse cutoff switch that trips (opens the circuit) if an excessive current draw occurs, cutting power to prevent damage, fire, or a drained battery. What it does It sits between the battery and the vehicles main electrical circuits