How Long Can a 24V Car Fan Run After the Engine is Off?
3 Answers
If the car fan is 24V, it still depends on the battery capacity. Under normal circumstances, a 24V car fan can run for three to four hours without worrying about draining the battery. If the battery has a larger capacity, it can last even longer. Here is some relevant information: Car Electric Fan: The car electric fan is controlled by a thermostat. When the water temperature rises to the upper limit, the thermostat turns on the power, and the fan starts working. When the water temperature drops to the lower limit, the thermostat turns off the power, and the fan stops working. Precautions: After parking, try not to use electrical appliances for a long time to avoid draining the battery and causing difficulty in starting the car, which can damage the battery. Using it for less than an hour is generally fine, but if it exceeds an hour, either turn off the electrical appliances or start the car to charge the battery and prevent it from being drained.
I play around with cars a lot. How long a 24V car fan can run after the engine is turned off depends on several factors. First, consider the battery capacity. 24V systems are usually found in trucks and buses, which often have large-capacity batteries, like 100Ah ones. As for the fan power, small fans are around 30W, consuming less power, while larger fans can be 100W or more. To calculate the runtime: Time (hours) ≈ Battery capacity ÷ (Fan power ÷ 24). For example, with an 80Ah battery and a 60W fan, current = 60 ÷ 24 ≈ 2.5A, time = 80 ÷ 2.5 ≈ 32 hours theoretically. In reality, it’s less than half of that because battery discharge efficiency isn’t high, and there’s standby power consumption from systems like the alarm. It’s worse with an old battery or in cold weather. From my experience, don’t rely on it for too long—keep it under an hour or two after turning off the engine, or the battery might drain and fail to start. I recommend regularly checking battery health to extend its lifespan.
As a long-distance truck driver, I frequently use a 24V fan in my vehicle. How long can it last after turning off the engine? It depends on the fan size and battery condition. Small fans with lower power can run for about four to five hours; medium-sized fans may last two to three hours. My old battery last summer triggered a low-voltage warning after just one hour of fan use, while a new battery lasts longer. Ambient temperature also plays a significant role—in winter or rainy conditions, the battery drains much faster. For safety, I usually run the fan for only half an hour before taking a break and restarting it later. Remember to turn off other devices like headlights or audio systems to extend usage time. Using the fan after engine shutdown is for emergencies, not as a substitute for air conditioning. Make sure to charge the battery a bit before parking.
