Practical relay that protects the Hydrogenerator Wave 3 GD/GS charger from overvoltage. The relay measures the generator voltage level and, if necessary, breaks the connection between the outboard unit and the charger in the event of an overvoltage to prevent damage. This can occur at higher speeds. When the speed of the boat decreases and the generator voltage drops, the relay restores the electrical connection between the generator and the charger and the charging function resumes. The relay receives the electrical energy it needs for operation from the generator and is ready for operation as soon as the boat is moving.