It is not recommended to connect a 12-volt auto alternator to a 24-volt system. The alternator is designed to provide a specific output voltage, and attempting to charge a 24-volt system with a 12-volt alternator can cause damage to the alternator or the batteries.
In order to charge a 24-volt system, a 24-volt alternator must be used. This will ensure that the correct voltage is provided to the batteries, preventing any potential issues.