Which measurement is crucial for assessing battery health aside from voltage?

Specific gravity is a critical measurement for assessing battery health because it provides insight into the battery's state of charge and overall condition. This measurement indicates the density of the electrolyte solution in lead-acid batteries and reflects how well the battery can hold a charge. By testing the specific gravity using a hydrometer, you can determine whether the battery is fully charged, partially charged, or discharged. A healthy battery should have specific gravity readings that fall within a specific range for a fully charged state, and deviations from this range can indicate issues such as sulfation or weak cells.

In contrast, while voltage drop is important for diagnosing current flow and resistance in a circuit, it doesn't give the full picture of battery health. Amperage draw can help identify how much current the vehicle's electrical systems are using, but it doesn't directly reflect the battery's ability to hold charge. Temperature can impact battery performance and is also essential in diagnosing thermal issues, but it does not provide a complete assessment of the battery's state of health like specific gravity does. Thus, specific gravity stands out as the key measurement for evaluating battery health beyond voltage.