The charging time of a 12V battery varies depending on several factors, such as the capacity of the battery, the current of the charger, and the current state of the battery. In general, charging a 12V battery can take from a few hours to several days.

A rough estimate of the charging time can be made by dividing the capacity of the battery by the charging current. Suppose you have a 12V battery with a capacity of 100 amp-hours (Ah) and you use a charger with a charging current of 10 amperes (A), then the charging time would be approximately 10 hours. However, keep in mind that this is only an estimate and that the actual charging time may vary.

It is important to emphasize that safe and efficient charging of a 12V battery requires using a charger that is suitable for the type of battery you have. Ensure that you follow the manufacturer's recommendations regarding the charging procedure and charging times.

Additionally, factors such as temperature and the condition of the battery can affect the charging time. A damaged or aging battery may take longer to charge or may not charge properly.

Always consult the manual or specifications of your specific battery and charger for accurate information on the charging time and the recommended charging procedure.