Connecting the device to charge the battery
For vehicles with a battery in the trunk: connect the positive cable to the positive battery terminal, and the negative cable to the negative terminal.
In cars with a battery under the rear seat: connect the positive wire to the "+" terminal in the engine compartment, and the negative wire to the bare metal of the engine cylinder block.
The battery can remain in the vehicle while charging.
It is not necessary to remove the battery cables if the charger is weak.
The battery caps can remain installed. The gas generated during charging will be able to escape through the ventilation holes in the cap.
The charging current should initially be approximately 10% of the battery capacity (for example, 5 A with a 50 Ah battery) and automatically decrease during the charging process.
The battery is fully charged if the acid density does not rise within two hours.
When charging a battery, distilled water partially disintegrates, forming gas bubbles of hydrogen and oxygen - highly explosive detonating gas.
Therefore, it is necessary to ensure good ventilation of the room; especially if high current charging occurs.
When charging the battery, do not smoke nearby or use open flame.
Oxygen gas can also be ignited by a spark when installing or disconnecting the charger or battery cables.
(A link to the original source is available on the website AudiManual.ru)