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Battery, state of charge, check (Measure specific gravity)
Disconnect the battery cables or switch off the battery master switch of new or used vehicles in
stock or out of operation.
Every battery, however, is provided with a self-discharge, that is, it discharges itself.
Thus, during the delivery service in a new vehicle, check that the density of the electrolyte is
within the specified values. Otherwise, charge the batteries slowly.
1.25 = Fully charged battery
1.22 = Battery in need of extra charge
1.18 = Discharged battery
Below 1.13 = Fully discharged battery. If not immediately charged, the battery will be made
useless.
The density of the electrolyte is measured with an air gauge-type densimeter.
The density depends on the concentration of sulfuric acid and it varies with the temperature.
Density increases when the temperature goes down and it decreases when the temperature goes up.
The electrolyte of a fully charged battery has a temperature of + 27°C and a density of 1.25 g/cm³.
Calculation of the temperature compensation in a densimeter (in case it is not provided with
temperature compensation)
The density of the electrolyte (D) should be between 1.24 - 1.26 g/cm3 at a temperature of 27°C in a fully charged battery. If the electrolyte temperature measured close to the battery centre is other
than 27°C, adjust the density using the formula below:
D(27°C) = D1 + 0.0007 x (T – 27)°C
D(27°C) = density to be obtained (g/cm³)
D1 = measured density
T = battery temperature in °C
Example:
The following information has been obtained:
– Measured density (D1) = 1.235 g/cm³
– Temperature 40°C
D(27°C) = 1.235 + 0.0007 x (40 – 27)°C
D(27°C) = 1.235 + 0.0007 x 13°C
D(27°C) = 1.235 + 0.0091°C
D(27°C) = 1.244 g/cm³
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