Early morning, temperature in the high 30s, car was not plugged in all night. Plugged in the 110V charger and shortly after noticed a slight/quiet crackling sound emanating from the lower section of the car, about where the batteries are located. I assume that this was the batteries and/or battery cases undergoing thermal expansion. The sound stopped after a few minutes. The car ran fine. The next day I left it plugged in all night, not surprisingly all was quiet as a mouse. Has anyone else noticed this.