Volkswagen Workshop Service and Repair Manuals

Notes:

• ◆ Smoking or the use of naked lights are not allowed in rooms in which batteries are being charged. The reason for this is, that when batteries are charged gases are produced which are highly flammable.
• ◆ Precision tools should be kept well away from such rooms. The reason for this is, that when batteries are charged the air in the room reacts chemically and this causes corrosion.

Special tools, testers and auxiliary items

• ◆ Batteries should be charged using a V.A.G battery charging unit e.g. V.A.G 1471, V.A.G 1648 or V.A.G 1974.

Notes:

• ◆ The battery charging unit must always be switched off before a battery is to be connected to the charging unit.
• ◆ Before charging a battery it must have a temperature of min. 10 °C.
• ◆ Batteries should be charged using a V.A.G battery charging unit e.g. V.A.G 1471, V.A.G 1648 or V.A.G 1974.
• ◆ Adhere to the points for no load voltage and electrolyte density if the battery is to be used again in the vehicle.

Performing battery charging

• ‒ Disconnect earth and positive cables from the battery.
• ‒ Connect battery to charging unit, positive to positive, negative to negative.

Procedures for totally discharged batteries

• ◆ Batteries that have not been used for a long time e.g. vehicles that have been stored, self discharge through consumers (e.g. clock). If this occurs the batteries sulphate and the complete outer surface area hardens on these batteries.
• ◆ If these totally discharged batteries are charged quickly from this totally discharged state then the sulphation dissipates. If this is not done the plates harden even more and the ability to accept a charge is reduced. A reduction in the energy reserve is the result.
• ◆ On totally discharged batteries the electrolyte (sulphuric acid/water mixture) is almost all water, the sulphuric acid part is heavily reduced. At minus temperatures the fluid in these batteries expands and the battery housing cracks.
• ◆ When totally discharged batteries are charged quickly, with normal battery charging units, they accept no charging current or through surface charging are shown as "full". They appear to be OK. Such batteries must be charged with a low charging current as described in the following:

Charging prerequisites for totally discharged batteries

If a totally discharged battery (no load voltage of 11.6V "Volt" and less), the charge time must take at least 24 hours and more. The charge current (Imax) must only be a maximum 10% of the battery capacity, e.g. for a 60Ah battery the charge current, Imax = 6A (Ampere). The charging voltage (Umax) must only be maximum 14.4V (Volt).

Totally discharged batteries must never be charged quickly.