Q: Fan and Battery

Any electrical device that is left on (or that is "stuck" on), while the car is not running, will drain the battery. The rate at which the battery will be discharged depends on the amount of current (amps) drawn by the device, in your case a fan. Very roughly, an automobile storage battery might have a capacity of 50-100 amp hours (amp hours, not the battery’s CCA rating which is much higher). If your fan requires 120 watts, then it is drawing about 10 amps. After 5 to 10 hours the battery will be dead. If you need your battery tested, recharged, or have an electrical issue, the recommended service to request is an electrical components diagnostic. If you request that service, the responding certified mechanic will diagnose any fault you are experiencing and estimate the required repairs and cost. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.