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No-load voltage measurement > < Visual inspection

A3 Mk1

Electrical system
Battery
Checking electrolyte level
Attention:
Always heed accident prevention regulations when handling electrolyte.
Always wear suitable protective clothing.
Only use torch to illuminate inside of battery casing.
Never illuminate inside of battery casing with a naked flame.
Keep naked flames and burning cigarettes away from batteries.
When disposing of batteries, always pay attention to the appropriate regulations for batteries and sulphuric acid.
To ensure that the various battery cover systems do not leak, only screw genuine battery caps into battery openings. In the event of loss or damage, make exclusive use of genuine caps of the same type.
The caps must be fitted with an O-ring seal.
 
W00-0970

Special tools and workshop equipment required

  • ◆ Battery filler VAS 5045
  • ◆ Commercially available hydrometer

Notes:

  • ◆ The correct electrolyte level is an important factor in ensuring a long battery service life.
  • ◆ On batteries with visiblemin. and max. marks, electrolyte level can be checked simply by visually inspecting outside of battery.
  • ◆ Electrolyte level must be above min. mark, but must not exceed max. mark.
  • ◆ On batteries on which the outermin. and max. marks are difficult to see or proper checking of the electrolyte level cannot be guaranteed on account of the opaque nature of the battery casing, the caps have to be unscrewed. The electrolyte level can then be checked by way of a visual inspection of the inside of the battery.
  • ◆ The electrolyte level must coincide with the internal level mark (plastic web). This corresponds to the outer max. mark.
 
A27-0086
  • ◆ → On batteries with a magic eye -arrow-, the electrolyte level can be established from the colour indicator.
  • ◆ Test sequence
 
N27-0129

Electrolyte level too low

Note:

If the electrolyte level is too low, drying-out of the cell plates will reduce the capacity (power) of the battery. If the cell plates are not surrounded by electrolyte, the plates, plate links and cell connectors will become corroded. The function of the battery is then not guaranteed and it becomes unusable.

  • ‒ → If the electrolyte level is too low, use battery filler bottle VAS 5045 to top up distilled water as far as max. mark.

Notes:

  • ◆ The filler neck of the filler bottle VAS 5045 is designed to prevent over-filling of the battery cell and electrolyte leakage. The flow of distilled water into the battery cell is interrupted on reaching the max. level.
  • ◆ Always use distilled water for topping up to prevent electrolyte contamination which results in increased self-discharge.
  • ‒ Screw battery cell caps back in again => Page 27-16 (batteries with central gas venting system).
 
N27-0094

Electrolyte level too high

Note:

If the electrolyte level is too high, escaping electrolyte (mixture of sulphuric acid and water) will cause damage outside the battery, e.g. on components in the engine compartment.

  • ‒ → If electrolyte level is too high (overfilled), i.e. if level is above inner electrolyte mark (plastic web) or above outer max. mark, excess electrolyte must always be drawn off using a commercially available hydrometer.
  • ‒ Use hydrometer to draw off sulphuric acid until electrolyte level reaches plastic web/max. mark.
  • ‒ Screw battery cell caps back in again => Page 27-16 (batteries with central gas venting system).

No-load voltage measurement > < Visual inspection