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Rapid-charging battery > < Measuring voltage under load

A4 Mk1

Charging battery
Charging battery
Special tools and workshop equipment required
   
t  Battery charger -VAS 5900- or
  W00-10182
t  Battery charger -VAS 5903-
  Note
t  Battery chargers -VAS 5900- and -VAS 5903- charge without current and voltage peaks. Batteries can therefore also be charged when installed. Safety precautions must be heeded when doing so. Both chargers have a back-up function enabling them to supply power to circuits.
t  To prevent damage to the battery, it must be connected to a charging unit with back-up mode to work on the electrical system when system components are periodically switched on.
Procedure
  WARNING
t  Ensure good ventilation.
t  Smoking or the use of naked lights are not allowed in rooms in which batteries are being charged. The reason for this is that inflammable gasses are formed during the battery charging process.
t  Heed safety regulations of the charger and battery manufacturers.
t  Rapid-charging of battery → Chapter.
–  Switch off battery charger.
  Caution
On vehicles fitted with telematics system, activate service mode of telematics control unit before disconnecting battery → Communication; Rep. Gr.01 or → Rep. Gr.91.
–  Switch off ignition.
  W00-10436
–  If fitted, detach rubber seal of plenum chamber cover in direction of -arrow-.
–  Remove plenum chamber cover -1- to front.
  A20-0564
–  If fitted, fold up cover over positive terminal.
–  Disconnect earth cable -1- and positive cable -2- at battery.
  A27-0013
–  Connect clamp -5- of positive cable of battery charger -1- to battery positive terminal post -4- and clamp -2- of earth cable of battery charger to battery earth terminal post -3-.
  Note
Illustration shows battery removed.
–  Adjust the charging current on the charger according to the battery capacity.
l  The charging current should be around 10 % of the battery capacity (so for a 60 Ah battery around 6 A).
–  Switch on the battery charger.
Reassembly is carried out in the reverse order; note the following:
–  Connect battery. Additional steps required → Anchor.
Exhausted batteries
t  Batteries which have not been used for lengthy periods, e.g. in vehicles which have not been driven, are subject to self-discharge.
t  A battery is considered to be exhausted if the no-load voltage has dropped below 11.6 V. Initial battery damage can occur between 12.2 and 11.6 V. Measuring no-load voltage → Chapter.
t  In an exhausted battery the electrolyte (sulphuric acid/water mixture) is reduced to almost all water, as the sulphuric acid content is heavily reduced. At temperatures below zero, the battery may freeze and the cause the housing to burst.
t  Exhausted batteries become sulphated, i.e. the entire battery plate surfaces harden. The electroyte has a slightly milky appearance (instead of being clear).
t  If exhausted batteries are charged directly after being discharged, the sulphation dissipates.
t  If this is not done, the plates become even harder and the battery's ability to absorb charge is impaired. This results in reduced power output.
Procedure for charging exhausted batteries (sulphated)
Exhausted batteries (that are also sulphated) 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.
Charging battery → Chapter. The charging voltage (Umax) must not exceed 14.4 V.
  Note
Do NOT attempt to rapid-charge exhausted batteries.
  A27-10053

Rapid-charging battery > < Measuring voltage under load