Specific Gravity of the electrolyte is a vital parameter which needs to be periodically measured and recorded. The specific gravity of the Electrolyte gives us an indication of the level of charge in the battery.
Specific gravity of any substance is the ratio of the density of that substance to the density of water. It does not have any unit as it is a ratio. Specific Gravity is also known as Relative Density. Specific gravity is measured using a hydrometer (see picture).
A higher specific gravity of an electrolyte is caused when the water content in the electrolyte is reduced either due to electrolysis or evaporation. A lower specific gravity would indicate undercharging.
During the charge-discharge cycle of a battery, the specific gravity varies continually. It increases when the battery gets charged and decreases when the battery gets discharged.
Specific gravity of the electrolyte also varies in accordance with temperature, it decreases with increase in temperature and increases in colder conditions.
