Battery, Charging
Battery
The battery is one of the most important electrical components in the vehicle. Its proper functioning is a major factor in ensuring customer satisfaction. To guarantee a long service life, the battery must be checked, serviced and maintained as described in this service information.
In addition to its function of starting the vehicle, the battery performs other tasks as a buffer and a source of electrical energy for the vehicle's entire electrical system.
Battery, Charging
Special tools, testers and auxiliary items required
• Battery charger
The battery should be charged using a battery charger (VAG), for example (VAG 1471), (VAG 1648) or (VAS 1974).
CAUTION!
The battery plugs must be fully tightened when charging, measuring voltage or performing load tests.
Rooms in which batteries are charged must not be entered with a open flame or while smoking. As the battery forms gas which is readily flammable during the charging process.
• The battery temperature must be at least 10 °C.
• Batteries should only be fast charged (e. g. boost starting) in exceptional circumstances; as fast charging causes damage.
• If fast charging is performed on heavily discharged 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.
Procedure
See Caution before beginning repairs on the electrical system => [ Battery ] Battery
- Switch off battery charger.
- Note and if necessary, determine radio code for vehicles equipped with coded anti-theft radio / radio navigation system only foreign brands).
- Switch ignition off.
- Push cover over battery to the right - arrow 1 - and remove by lifting off - arrow 2 -.
- Disconnect Ground strap - 1 - on battery negative terminal and detach positive cable - 2 - on battery positive terminal.
- Connect positive lead of battery charger to positive terminal of battery.
- Connect negative lead of battery charger to negative terminal of battery.
- Adjust charge current at battery charger according to battery capacity. It should amount to approx. 10% of the battery capacity. For a 60 Ah battery, approx. 6 A.
- Switch on battery charger.
Installation is reverse of removal, paying attention to the following:
- Connect battery. Required steps.
Notes on heavily discharged batteries:
Batteries which have not been used in driving operation for a long time, for example in stored vehicles, discharge themselves.
A battery is heavily discharged, if the no-load voltage has dropped below 11.6 V. Measuring no-load voltage => [ Battery, Checking No Load Voltage ]
In severely discharged batteries the electrolyte (a mixture of sulfuric acid and water) consists almost entirely of water, since the proportion of sulfuric acid is strongly reduced. At minus temperatures, the battery can freeze and the housing can crack.
Heavily discharged batteries become sulfated, i.e. all the plate surfaces of such batteries become hard. The electrolyte is not clear, it has a slightly white color.
If a heavily discharged battery is recharged immediately after heavy discharge, the sulfation can be reversed.
If these batteries are not recharged, the plates continue to harden and the charge-retention ability becomes limited. The consequence is reduced battery performance.
Procedure for Charging Heavily Discharged Batteries
Heavily discharged batteries, which have become sulfated, must be charged as follows using a low charging current:
- Adjust charging current to approx. 5% of the battery capacity, i.e. for a 60 Ah battery the charging current is approx. 3 A (ampere).
Charging battery => [ Battery, Charging ].
The charge voltage (Umax) may only amount to a max. of 14.4 V (volt).
Severely discharged batteries should never be charged quickly.