What is the normal specific gravity of a fully charged lead acid battery cell?

The normal specific gravity of a fully charged lead-acid battery cell is approximately 1.280, which is why this choice is correct. Specific gravity is an important indicator of the charge level in a lead-acid battery; when fully charged, the electrolyte solution's density increases, resulting in this specific gravity reading.

In practical applications, a hydrometer is often used to measure the specific gravity of the battery electrolyte. The exceptional value of 1.280 signifies that the battery cell is functioning optimally and is fully charged, while lower values indicate varying levels of charge or potential issues with the battery's state.

In contrast, specific gravities such as 1.375 and 1.180 do not represent the correct state of a fully charged lead-acid battery. The value of 1.210 also does not accurately reflect a fully charged condition, as it suggests the battery is only partially charged or has a different composition. The correct understanding of specific gravity helps in battery maintenance and ensuring reliable power supply in maritime communication equipment.