Table 7-3. Electrolyte density at 25°C, g/cm³
If the battery is discharged more than 25% in winter and 50% in summer, remove it from the car and recharge it.
When measuring the density, make sure that drops of electrolyte containing sulfuric acid, which causes corrosion, current leakage, etc., do not fall from the pipette onto the surface of the battery, the body, or other objects.
The density of the electrolyte depends on the temperature. With every 15°C change, the density changes by approximately 0.01 g/cm³. Therefore, if the electrolyte temperature is higher or lower than 25°C, add to the hydrometer reading or subtract from it the temperature correction:
| Electrolyte temperature,°C | Correction, g/cm³ |
| from -40 to -26 | -0,04 |
| from -25 to -11 | -0,03 |
| from -10 to +4 | -0,02 |
| from +5 to +19 | -0,01 |
| from +20 to +30 | 0,00 |
| from +31 to +45 | +0,01 |
To avoid getting erroneous results, do not measure the density of the electrolyte:
- if its level is not normal;
- if the electrolyte is too hot or cold; the optimal electrolysis temperature for density measurement is 15-25°C;
- after adding distilled water, you should wait until the electrolyte moves; if the battery is discharged, this may even take several hours;
- after several starts, you should wait until the electrolyte density in the battery element is uniformly established;
- when the electrolyte is "boiling" 4, you should wait until the bubbles in the electrolyte, collected in the hydrometer pipette, rise to the surface.
If the electrolysis density is too low (less than 1.22 g/cm³) and at the same time there is strong heating of the battery during operation (more than 10°C above the ambient temperature) or the density of the electrolyte in different elements of the battery differs by more than 0.2 g/cm³, then in these cases recharge the battery with a current of 2-3 A for 24 hours. If after recharging the battery voltage is less than 12 V, then it is not suitable for operation.
If, when measuring the specific gravity of the electrolyte, it is found to be excessively high (1.3 g/cm³ and above), then bring it up to the norm as indicated below.