To charge a 12V battery, you need a 14V generator. Of course, car bulbs will account for this voltage difference. In fact, the calibrated voltage and the actual voltage of all electrical appliances are different, as long as they are within a certain range, there is no problem.
When you suspect that the generator is not producing electricity, you can check it on the car without disassembling the generator to roughly determine whether there is a fault.
Judgment method
When driving the car, turn the multimeter knob on the end of the battery to the DC voltage range of 30V, connect the wire of red test to the "armature" terminal of the generator, and the black test lead to the case, let the motor run above the average speed, the standard voltage value of the 12V electrical system should be around 14 V and the valueThe standard voltage of the 24 V electrical system should be around 28 V. The measured voltage of a car is usually above 13.8 V, often reaching over 14 V.