Specific gravity, checking
WARNING:
- Prior to handling or servicing batteries, read, understand and observe the Warning and Safety Measures for lead-acid batteries. Refer to Warnings and Safety Measures for lead-acid batteries .
- Dispose of electrolyte (sulfuric acid) properly! Waste electrolyte must only be disposed of in appropriate waste disposal sites. Refer to local regulations pertaining to electrolyte disposal.
- The following notes and procedures must be followed to ensure correct measurements.
Special tools and auxiliary items needed
- Commercially available hydrometer
- Shop rags
NOTE:
- Checking specific gravity shortly after topping up with distilled water will result in erroneous readings. Charge battery after topping up with distilled water, then check specific gravity.
- Minimum battery temperature of 10 ° C (50 ° F) is required when carrying out specific gravity tests.
- Specific gravity of all cells must be checked.
CAUTION:
Before beginning repairs on the electrical system
- Switch off all electrical consumers.
- Switch ignition off and remove ignition key.
- Remove all battery cell caps.
- Dip end of hydrometer into cell and extract sufficient electrolyte to allow indicator float to swim freely (the greater the electrolyte density in kg/dm3, the higher the indicator float position). Note each cell's specific gravity reading from float -arrow-. Repeat sequence until all cells are checked.
- Review noted values and compare with values in table below:
| Charge condition (normal climate) | Specific gravity in kg/dm3 |
| Discharged | 1.15 |
| Half charged | 1.22 |
| Fully charged | 1.28 |
- Electrolyte density must be at least 1.24kg/dm3
- If specific density is too low, charge battery and recheck specific density afterwards.
- Electrolyte density must not vary more than 0.04kg/dm3 between cells.
Examples of unacceptable variations in specific gravity:
| Specific gravity variations per cell in kg/dm3 | ||||||
| Cell Number: | 1 | 2 | 3 | 4 | 5 | 6 |
| Example 1: | 1.24 | 1.25 | 1.25 | 1.10 | 1.24 | 1.25 |
| Example 2: | 1.26 | 1.26 | 1.25 | 1.14 | 1.18 | 1.24 |
Example 1: Specific gravity in cell 4 (1.10) is too low.
Example 2: Specific gravity in cells 4 (1.10) and 5 (1.18) are too low and variation between cells exceeds 0.04kg/dm3.
If specific gravity specifications are not met, replace battery.
If specific gravity specifications are met, reinstall cell caps.
CAUTION:
Only the use of genuine VW battery cell caps ensures the different battery cover systems are sealed correctly. Only use genuine cell caps of the same construction if lost or damaged. All cell caps must be equipped with an O-ring seal.