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

A rough estimate of the charging time can be made by dividing the battery's capacity by the charging current. Suppose you have a 12V battery with a capacity of 100 ampere-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 the actual charging time may vary.

It's important to emphasize that safely and efficiently charging a 12V battery requires using a charger suitable for the type of battery you have. Make sure to follow the manufacturer's recommendations regarding the charging procedure and charging times.

Additionally, factors such as temperature and the battery's condition 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 charging time and recommended charging procedure.