As night falls, you connect your car to the charging pile for a rest, but you hear a continuous “buzzing” sound coming from the chassis; or on the way of fast charging, the sudden high-speed operation of the fan breaks the tranquility of the garage-does such a scene make you doubt?
According to statistics, more than 80% of EV owners will have safety anxiety when they first encounter charging noise.
In fact, these sounds, like cicadas chirping in summer, are the unique language given to electric vehicles by industrial design.
They are mainly derived from the electromagnetic vibration of the high-voltage electrical system, the efficient operation of the cooling fan and the micro-movement of lithium ions in the battery.
When the charging gun and the vehicle complete the “handshake protocol”, the current flows in the vehicle body like blood, accompanied by the low roar generated by heat exchange, the light sound of high-frequency switching power supply, and even the crisp “click” when the relay is on and off, which constitutes the vital signs of electric vehicle charging.
Understanding the code of these sounds will help us free ourselves from unnecessary worries.
The sound of EV when charging is mainly the physical manifestation of the cooperation of their high-voltage electrical system, cooling system and electrochemical process.
Most of these sounds are normal, but some abnormal noises may indicate equipment failure.
- Working sound of cooling system (most common)
The fan is running at high speed
During charging, components such as battery packs, chargers, and DC-DC converters generate a large amount of heat due to current conversion. When the temperature exceeds 40 ℃, the cooling fan starts; When entering the high-speed mode above 50 ℃, the noise increases significantly. In high temperature environment or fast charging scene, the fan needs higher speed to dissipate heat, and the sound is more obvious.
Sound characteristics: continuous low-frequency “buzzing” or “whirring” sound, similar to the outdoor unit of air conditioner.
Sound of liquid cooling pump circulation
Some models use liquid cooling system, which may produce the sound of running water when the coolant flows, especially when the battery temperature rises rapidly.
2.Working sound of electrical system
Noise of high frequency switching power supply
The car charger uses high-frequency switching power supply technology to regulate voltage and current through fast on-off (thousands of times per second). The action of the switch causes an electromagnetic vibration that translates into an audible hum.
Relay closing/opening sound
At the beginning or end of charging, the high voltage relay (electromagnetic switch) turns on and off the large current, producing a crisp “click” sound. This is the sign of safe start and stop of the high voltage system.
Current high-frequency sizzling sound
When current flows through transformers and inductors, the electromagnetic field causes the components to vibrate slightly, producing a high-frequency current sound similar to that of an old TV. It is easier to detect when charging slowly.
- Battery system related sound
Sound of expansion with heat and contraction with cold
The heat from charging the battery causes the metal shell and internal structure to expand and contract as it cools, producing a slight “crackling” sound. It is more significant after fast charging in low temperature environment.
Electrolyte reaction sound
When lithium ions migrate in the electrolyte, they produce bubbles and micro-vibration, and make a weak “hissing” sound, which can be detected in a quiet environment.
- Noise of the charging pile itself
The DC fast charging pile has a built-in high-power transformer and cooling fan, which produces a low buzz when working, which may be transmitted to the car through the charging line.
5.Be alert to abnormal noise (possible fault)
The following sounds may indicate equipment problems, and it is recommended to repair them in time:
① Sharp metal friction sound → oil shortage or damage of fan bearing
② Crackling sound of continuous current + burnt smell → short circuit or component aging
③ The fan runs wildly with the interruption of charging → the cooling system is dusty or the sensor is faulty.
Therefore, most charging sounds are inevitable products of technical design, and there is no need to worry too much. However, if the noise changes suddenly, accompanied by odor or instrument alarm, it is necessary to check the fault immediately. Noise can be significantly reduced by regularly cleaning the dust at the radiator and avoiding charging in high temperature environment.
The lingering sound of the fan at the end of charging, or the mechanical sound when the relay is disconnected, is not the alarm bell of the fault, but the certification signature of the safe power off of the high-voltage system.
Just as the roar of turbine engines was once the identity of fuel vehicles, these controllable physical acoustic phenomena are the unique expression of EVs as precision electromechanical integration.
We encourage car owners to develop the ability to “listen to the sound and recognize the car”: to identify the healthy state of the uniform low-frequency buzz of the cooling system, and to be alert to the dangerous signals of sharp metal friction or continuous current burst.
When you understand that the high-speed operation of the fan is to protect the safety of the battery at a high temperature of 50 degrees Celsius, and the “click” sound of the relay represents the safe quarantine of the 10,000-volt high voltage, you will understand that these sounds are the proof of the vehicle’s due diligence in protecting the driver.
Keep the radiator clean, avoid charging in the hot sun, and let your car play a quiet and reliable future movement in the temperature of science and technology.
