Those of you who run an S-Type will be well aware of how sensitive the car's electronics is to voltage drop. In the old days, eventually your starter motor would begin to exhibit a distinct lack of torque to start the engine and that warned you to charge the battery. In our cars, the system throws a wobbly at the slightest voltage drop, well before the starter has trouble. All you get is a plethora of fault codes and the immobilizer refuses to disengage.   I, along with other