Which test determines a battery's ability to deliver current under load?

The high-rate discharge test is designed specifically to evaluate a battery's ability to provide a significant amount of current within a short period, which simulates the conditions a battery experiences during typical starting applications. By applying a load that simulates the cranking of an engine, this test measures the battery's performance and its ability to sustain voltage levels. If the battery can maintain acceptable voltage under this load, it indicates that the battery is in good working condition and capable of delivering the necessary current.

In contrast, the hydrometer test measures the specific gravity of the battery electrolyte, which can provide information about the state of charge but does not directly evaluate how well the battery performs under load conditions. The resistance test assesses the internal resistance of the battery, which can indicate its capacity but again does not focus specifically on load performance. The voltage drop test monitors voltage drops across connections under load, helping identify poor connections or wiring issues rather than directly assessing the battery's output capability. Each of these other tests serves a specific purpose but does not replicate the conditions necessary to determine how well a battery can deliver current under load, making the high-rate discharge test the appropriate choice for that evaluation.