What is an acceptable charging circuit voltage range for a 12 volt system?

In a 12-volt electrical system, the normal operating voltage when the engine is off should be around 12.6 volts, indicating a well-charged battery. However, when the engine is running and the alternator is actively charging the battery, the voltage can increase. An acceptable charging circuit voltage range typically falls between approximately 13.5 to 15.0 volts. This range ensures that the battery receives adequate charging while preventing overcharging, which can damage the battery and the electrical components.

When the voltage exceeds this range, particularly above 15 volts, there is a risk of boiling the battery electrolyte or causing damage to sensitive electronic components in the vehicle. Therefore, the specified range effectively balances the need for efficient charging while maintaining the health of the battery and the overall electrical system.