Audi Workshop Service and Repair Manuals

Special tools and workshop equipment required

• ◆ Battery charger

The battery should be charged using a V.A.G battery charger, e.g. V.A.G 1471, V.A.G 1648 or VAS 1974.

Notes:

• ◆ The battery temperature must be at least 10 °C.
• ◆ Rapid charging of batteries should only be performed in exceptional circumstances (e.g. boost starting) as rapid charging causes damage.
• ◆ If rapid charging is performed on exhausted batteries, they fail to absorb any charging current or register as being fully charged prematurely due to so-called surface charging. They appear to be OK.

Sequence of operations

• ‒ Switch off battery charger.

• ‒ Heed (if necessary obtain) code for vehicles with encoded radio/radio navigation system (RNS).
• ‒ Switch off ignition.

• ‒ Lay bare battery posts onwards.
• ‒ → Unfasten nut -3- several turns and disconnect pole shoe of earth wire from battery post.
• ‒ If applicable, unscrew nut -1- and detach busbar for main fuse box at pole shoe of positive wire.
• ‒ Unfasten nut -2- several turns and disconnect pole shoe of positive wire from battery post.

• ‒ → Connect positive lead of battery charger to positive terminal of battery.
• ‒ Connect negative lead of battery charger to negative terminal of battery.
• ‒ Set charging current on battery charger in line with battery capacity. It should be roughly 10 % of battery capacity (i.e. for a 60 Ah battery approx. 6 A).
• ‒ Switch on battery charger.

Install in reverse order, paying attention to the following:

• ‒ Connect battery. Action to be taken => Page 27-13.

Explanatory notes on exhausted batteries

Batteries which have not been used for lengthy periods, e.g. in vehicles which have not been driven, are subject to self-discharge.

A battery is considered to be exhausted if the no-load voltage has dropped below 11.6 V.
Measuring no-load voltage => Page 27-27

With exhausted batteries, the electrolyte (mixture of sulphuric acid and water) is more or less all water, with a greatly reduced sulphuric acid content.
At temperatures below zero, the battery may freeze and the casing burst.

Exhausted batteries become sulphated, i.e. all the plate surfaces of such batteries become hard. As opposed to being clear, the electroyte has a slightly milky appearance.

If an exhausted battery is re-charged immediately after exhaustive discharge, the sulphation can be reversed.

If this is not done, the plates become even harder and their ability to absorb charge is impaired, thus resulting in a loss of power reserves.

Procedure for charging sulphated exhausted batteries

Sulphated exhausted batteries must be charged as follows using a low charging current:

• ‒ Approx. 5 % of battery capacity, i.e. for a 60 Ah battery, the charging current is approx. 3 A (amps).

Charge battery => Page 27-38.
The charging voltage (Umax) must not exceed 14.4 V.

Rapid charging is never to be implemented on exhausted batteries.