Acid density

The unit showing the amount of sulphuric acid in the electrolyte and is a measurement of the battery voltage and charge status. The density of the acid is measured in g/cm³ . The higher the value of the acid density (i. e. high concentration of sulphuric acid), the higher the voltage and state of charge. A low acid density value means a correspondingly low concentration of sulphuric acid, low voltage and a reduced capability for providing current. The electrolyte in a fully charged battery has a density of 1.28 g/cm³ . The density of the electrolyte in a fully discharged battery is 1.10 g/cm³ .

HINT: For maintenance-free as well as sealed batteries (AGM) the battery acid cannot be accessed and thus its density cannot be measured.