Checking specific gravity of all cells — AUDI

Special tools and workshop equipment required

Commercially available hydrometer

Warning!
When using sulphuric acid it is absolutely necessary that the accident prevention procedures are observed. Suitable protective clothing must be worn.
When disposing batteries it is absolutely necessary that the disposal procedures for batteries and sulphuric acid are observed.
Notes:

In conjunction with the "voltage under load" test, the electrolyte density test gives a good indication of the battery condition.
The temperature of the electrolyte in the battery must be at least 10 °C.
The electrolyte density can be checked immediately after charging battery.

Test sequence

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.
The greater the specific gravity of the extracted electrolyte, the more the float rises.
The electrolyte density (in kg/dm3) can be read off the scale of the hydrometer (specific density of electrolyte).

Read off measured value on hydrometer and compare with table:

Charge condition in normal climates · Electrolyte density in kg/dm3
Discharged · 1.12
Half charged · 1.20
Well charged · 1.28

Charge condition in tropical climates · Electrolyte density in kg/dm3
Discharged · 1.08
Half charged · 1.16
Well charged · 1.23

In countries with normal climates the electrolyte density must be at least 1.24 kg/dm3.

If the electrolyte density is too low in all battery cells, charge the battery.
After charging the battery, repeat the electrolyte density test.
If the specifications are not obtained, renew battery.

Note:

The electrolyte density readings for the individual battery cells must not differ by more than 0.03 kg/dm3. Otherwise replace battery.

Battery cell: · 1 · 2 · 3 · 4 · 5 · 6
Electrolyte density per cell in kg/dm3
Example 1: · 1.24 · 1.25 · 1.25 · 1.10 · 1.24 · 1.25
Result: The electrolyte density in cell 4 is too low (deviation is greater than 0.03 kg/dm3)
Example 2: · 1.26 · 1.26 · 1.25 · 1.14 · 1.18 · 1.24
Result: The electrolyte density in cells 4 and 5 is too low (deviation is greater than 0.03 kg/dm3)

If the specifications are obtained, screw plugs in again.

Caution
To ensure effective sealing of the various battery cover systems, it is important to use the correct type of battery sealing plugs. If plugs are lost or damaged, always fit new plugs of the same type as originally fitted.
Each plug must be fitted with an O-ring seal.