The voltage drop indicates that the electrical current is flowing from the engine through various circuits to generate power for lighting, powering interior accessories, and moving parts of the vehicle's suspension or brakes. The lower this number, the more efficiently your car runs, and if you've recently been driving on. There are a few potential causes of voltage drop while cranking. The most common is the alternator not producing enough voltage to meet. A car battery typically needs 12-14 volts to start, and the voltage from a 9-volt battery won't get the engine going. A car battery with a reading of 9 voltsis. The batteryis a device used to store energy that supplies electrical power to run your vehicle's systems while driving and crank the engine. A low voltage drop while driving can result in stalling or a complete loss of power,. A low voltage drop can indicate a weak or failing battery, a bad alternator, or a problem with the electrical system. If the voltage drop is too low, it can prevent the engine from starting or result in poor performance. Ideally, the.