What is the specific gravity of a fully charged battery?

The specific gravity of a fully charged lead-acid battery is typically around 1.260. This measurement reflects the density of the electrolyte solution in relation to water, where pure water has a specific gravity of 1.000. A specific gravity of 1.260 indicates that the electrolyte solution, which consists of sulfuric acid mixed with water, is denser because it contains a higher concentration of acid when the battery is fully charged.

This density is important because it correlates with the state of charge in lead-acid batteries; a higher specific gravity usually means a fully charged state, while lower values indicate a discharged state.

Specific gravity readings that are significantly lower than this value can signal that the battery is sulfated or poorly maintained, which can affect performance and longevity. Understanding the specific gravity helps in assessing battery health and performance for maintenance and operation of outdoor power equipment.