Why does the fan keep running during new energy vehicle charging?

[Ian]

It is normal for the vehicle's fan to operate and produce noise during charging. When charging, the vehicle supplies high voltage to the battery. Due to the high voltage and current involved, this can easily cause the battery pack to overheat. The temperature sensors inside the battery will then send an alert to the BMS (Battery Management System). As the core component of the battery, the BMS will send a signal to the fan. Upon receiving this signal, the fan control terminal activates, causing the fan to start running. This is a normal and necessary process during electric vehicle charging. To put it simply, this mechanism is similar to a computer - when not under heavy load, the fan noise is barely noticeable, but once overloaded, the vehicle's fan noise becomes relatively louder.

[MacHector]

Last time when I drove my friend's pure electric car and encountered this issue, I initially thought it was a malfunction. Actually, it was due to the high heat generation during fast charging, which automatically activated the cooling system. All electric vehicles are equipped with a battery temperature control module. During charging, the BMS (Battery Management System) monitors the temperature, and once it exceeds the set value, the fan kicks in. This is especially noticeable during outdoor charging in summer or during high-current fast charging, when the fan noise becomes very obvious. It's similar to how a computer fan speeds up when gaming. Don't worry about overheating; instead, you should be concerned if the fan doesn't turn on. It's recommended to avoid charging during the high-temperature noon hours. Even after the car is turned off, the fan may continue to run for a few minutes until the temperature drops.

[StCameron]

From your description, it sounds like you encountered the liquid cooling system in operation. During charging of new energy vehicles, the DC power conversion process generates waste heat, and ternary lithium batteries require cooling when temperatures exceed 45°C. The coolant absorbs heat from the battery pack and then flows to the front radiator for cooling, a process that requires forced air cooling via fans. Once when I used a 120kW fast charger, the cooling fan was as loud as a hair dryer – which is actually a good sign, indicating the battery protection system is working diligently. During regular slow charging, less heat is generated, so the fan may not activate or may run at low speed. Next time you charge, feel the front bumper area – if the radiator zone is warm to the touch, that's perfectly normal.

[CharlesLee]

The fan operation during EV charging is an inevitable manifestation of the battery thermal management system at work. When the battery temperature reaches 30-35°C, the heat pump or AC compressor activates; exceeding 45°C triggers mandatory cooling fan engagement. I've observed fan operation even during sub-zero charging because the charging process inherently converts chemical energy into thermal energy. Manufacturers typically set conservative thresholds, prioritizing battery protection over fan runtime minimization. As long as there are no persistent abnormal noises, this is normal operation. Remember that fast charging generates over twice the heat of slow charging – continuous fan operation exceeding 30 minutes during supercharger use is commonplace.

[ONova]

This is a normal protective mechanism to cool down the power battery. Last year, when helping my cousin inspect his BYD, I noticed the cooling fan activated frequently during fast charging. Most new energy vehicles nowadays use active liquid cooling for heat dissipation, and the greater the charging current, the more severe the heat generated. It's similar to how your phone heats up while charging. I once used a thermal imager and observed that the surface of the battery pack could reach 50°C during fast charging. The fan blows away the heat from the radiator, much like a computer CPU cooler. Especially during hot summer days, the fan may run continuously from the start to the end of charging. The checking method is simple: if you feel warm air coming out from the fan vent at the front grille, it means the system is functioning normally.

[PrestonRose]

The reason lies in the fact that power batteries generate heat during both charging and discharging. During slow charging, the current is small, and the fan may operate intermittently; whereas during fast charging, the current can exceed 200A, leading to a significant increase in waste heat that must be continuously dissipated. This is actually the BMS intelligent temperature control system balancing the temperature. It's similar to how your body dissipates heat after exercise. Some car owners mistakenly pull out fuses to save electricity, only to trigger battery overheating alarms. At Tesla Supercharger stations, I've seen fans continue to run for several minutes after the owner unplugs the charging cable, which is due to residual heat in the cooling system not yet fully dissipated. Remember, the sound of the fan spinning is basically unavoidable during EV charging. On the contrary, if the sound becomes unusually quiet, it's necessary to have the cooling system checked for any blockages at the service center.