Checking the state of charge of the battery

If the battery does not work properly despite a normal electrolyte level, check the state of charge. To do this, use a hydrometer (automotive densimeter). The scale of the device shows the density of the electrolyte in the battery. You can also use an accurate universal measuring device (measurement accuracy±0.02 V). The voltage at the terminals of an unloaded battery indicates the state of charge of the battery.

Electrolyte Density Check

SEQUENCE OF WORK

1. Check only if the battery has been at rest for at least 6 hours.

2. Turn out (take out) corks from battery cans.



Pic. 15.5. Using a hydrometer to check the density of electrolyte in a battery

3. Draw enough electrolyte into the hydrometer so that the measuring float floats freely in it (pic. 15.5). On the scale on the float, determine the density of the electrolyte and determine the degree of charge of the battery from it. The degree of battery charge depending on the density of the electrolyte is given in Table. 15.1. With the same low electrolyte density in all banks, the battery is considered sufficiently charged. If only one battery cell is discharged, then the battery is defective and should be checked by a workshop.

Measurement of voltage at the battery terminals

If the last charge was carried out within the last 6 hours, turn on the dipped beam for 30 seconds. This will smooth out possible voltage drops.



Pic. 15.6. Using a multimeter to measure the voltage at the battery terminals

After 4–5 minutes, measure the voltage at the battery terminals (pic. 15.6). When measuring, turn off all consumers of electric current. If the voltage is less than 12.3 V at the battery terminals with the load disconnected, the battery must be charged. The degree of charge of the battery, depending on the voltage at the terminals, is given in Table. 15.2.