What is the most reliable method for testing a storage battery?

The most reliable method for testing a storage battery is the use of a high rate discharge cell tester. This device evaluates the battery's ability to deliver its rated capacity under conditions that are similar to what the battery would experience in real-world applications. By applying a load to the battery that simulates its operational demands, the tester can accurately assess how the battery performs under stress, providing crucial insights into its health and capacity.

This method is particularly effective because batteries may pass simple voltage checks but still fail under load. A high rate discharge test can reveal issues that would not be evident through other testing methods, such as a digital multimeter or hydrometer, which might show an acceptable voltage or specific gravity without accounting for the battery's performance under actual use conditions.