Audi Workshop Service and Repair Manuals

Measuring relative density of electrolyte in all battery cells Special tools and workshop equipment required

t  Refractometer -T10007- or

t  Hydrometer (commercially available) Procedure In conjunction with the battery check using the battery tester with printer -VAS 6161- → Chapter or using the battery tester with printer -VAS 5097A- → Chapter, the relative density test provides information on the charge state of the battery. l  The temperature of the battery electrolyte must be at least +10 °C.   WARNING Risk of injury when handling electrolyte. t  Observe safety instructions when handling battery electrolyte → Anchor. t  Wear eye protection and protective clothing → Anchor.   Note The relative density of the electrolyte can be checked immediately after charging the battery. –  Unscrew all battery cell sealing plugs.

–  Dip hydrometer into battery cell and draw in electrolyte until the float is floating freely 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 density of electrolyte) can be read off the hydrometer scale. –  Take reading on hydrometer and compare it to values given in table:

Charge state	Relative density of electrolyte in kg/dm3
	In normal climatic zones	In tropical countries
discharged	1.12	1.08
half charged	1.20	1.16
well charged	1.28	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 per battery cell in kg/dm3	1.24	1.25	1.25	1.10 1)	1.24	1.25
l  1) Relative density in battery cell 4 is too low (difference greater than 0.03 kg/dm3).

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

–  Renew the battery if the specified values are not attained.   Note The battery must be renewed if the relative density of the electrolyte measured in the individual battery cells varies by more than 0.03 kg/dm3.   Caution Danger from escaping electrolyte. t  The battery openings must be fitted with the correct type of genuine sealing plugs to ensure proper sealing of the battery cover (different types). Only use genuine sealing plugs of the same type when renewing missing or damaged sealing plugs. t  The plugs must be fitted with an O-ring. –  If specified values have been attained, screw sealing plugs of battery cells back in.   Note Observe disposal regulations if battery has to be renewed → Anchor.