Sound From Area Of Hybrid Battery

When I entered the garage today there was a humming sound coming from the area of the hybrid batteries. It had been 5 hours since our V was last driven. And in that 5 hours I had been in and out of the garage, even working a short time in the garage, and I never noticed any sound coming from the car. My wife also observed this.

I check the instrument cluster and there were no warning lights on. I went in the house and got the keys, pushed the power button, shut the car off, and the noise stopped.

Something was running in the rear of the car. I was wondering if it might be the battery fan. But I was baffled why it would turn on after several hours and continue to run until I powered the car up then stop.

Have any of my fellow V owners had this happen or have any ideas what was running in the rear of the car while parked? We're concerned something is amiss and if we hadn't caught it we might have gone out later and found a dead 12V battery. We've had the car three weeks and have 500 miles on it.

 

Thank you for the feedback and alleviating my concerns.

I thought it might be the fan, but I didn't think it would be running after the car sat idle for hours in a cold garage unless there was a malfunction. I scanned the manual, but obviously not good enough.

This a great forum and it's members are very knowledgeable and willing to educate us newbies on our Prius. If you need a question answered this is the place.