What is a common symptom of a failing battery?

A common symptom of a failing battery is delayed engine cranking or difficulty starting. This occurs because a battery that is losing its ability to hold a charge may not provide enough voltage or current to effectively power the starter motor. As a result, the engine may crank slowly, or there might be a noticeable delay before it starts or not start at all.

In contrast, normal engine cranking would indicate that the battery is functioning properly and providing adequate power. Bright dashboard lights typically suggest that the electrical system is working as it should, often related to a fully functional charging system rather than a failing battery. Increased fuel efficiency is not connected to battery health; instead, it pertains to the engine's performance and the efficiency of combustion processes. Therefore, the symptom of delayed engine cranking or difficulty starting is a reliable indicator of a failing battery.