Audi Workshop Service and Repair Manuals

Checking relative density of electrolyte for all cells - batteries with sealing plugs Special tools and workshop equipment required

t  Hydrometer (commercially available) or

t  Refractometer -T10007- Procedure   WARNING t  Always observe safety instructions when handling battery electrolyte → Anchor. t  Always wear suitable protective clothing → Anchor. t  When disposing batteries it is absolutely necessary that the disposal procedures for batteries and sulphuric acid are observed.   Note t  The electrolyte density test in conjunction with the battery load test provides specific information on the battery condition. t  The temperature of the battery electrolyte must be at least 10 °C. t  The electrolyte density can be checked immediately after charging battery. –  Remove all battery plugs (battery cell sealing plugs).

–  Immerse end of hydrometer in a cell and extract sufficient electrolyte so that float swims free in the electrolyte. t  The greater the relative density of the electrolyte drawn in, the higher the float will ride. t  The relative density in kg/dm3 (specific gravity of electrolyte) can be read off the scale -arrow- on the hydrometer. –  Take reading on hydrometer and compare it to values given in table:

Charge condition in normal climatic zones	Relative density of electrolyte in kg/dm3
discharged	1.12
half charged	1.20
well charged	1.28

Charge level in tropical countries	Relative density of electrolyte in kg/dm3
discharged	1.08
half charged	1.16
well charged	1.23

The relative density in normal climatic zones must be at least 1.24 kg/dm3. If relative density is too low in all battery cells: –  Charge battery and then repeat electrolyte relative density test. Example 1:

Battery cell:	1	2	3	4	5	6
Relative density of electrolyte per cell in kg/dm3	1.24	1.25	1.25	1.10 1)	1.24	1.25
l  1) Relative density in cell 4 is too low (difference greater than 0.03 kg/dm 3)

Example 2:

Battery cell:	1	2	3	4	5	6
Relative density of electrolyte per cell in kg/dm3	1.26	1.26	1.25	1.14 1)	1.18 1)	1.24
l  1) Relative density in cells 4 and 5 is too low (difference greater than 0.03 kg/dm 3).

If the specifications are not obtained: –  Renew the battery → Chapter.   Note The measured values for the electrolyte relative density of the individual battery cells must NOT deviate by more than 0.03 kg/dm3, otherwise battery has to be renewed. –  Screw sealing plugs of battery cells back in again.   Caution Battery openings must be fitted with the correct plugs to ensure that battery cover (different types!) is properly secured. Always use correct sealing plugs (same as original equipment) in the event of loss or damage. The plugs must be equipped with an O-ring seal.