Battery Vent Hiss

[vhmarx]

The other night while I was driving my '05 Prius I noticed a hissing sound coming from the back seat of my car.

Thinking it was the sound system I turned the volume down. It still was hissing so I turned the sound system off. I looked back and noticed that the sound was coming directly from the battery vent.

I drove for about 5 more minutes and it stopped.

Is there a fan in the battery compartment that comes on? It sounded sort of like that. Just wondering if anyone else had experienced this.

[galaxee]

cooling fan. completely normal and nothing ot worry about.

it's getting warmer out, you'll hear it now and then.

[ScottY]

Actually, I never heard the fan come on. When I monitor my battery temp on CAN-View, it was showing 92 degrees F. So I think, the fan MUST be on. So when I got back home and stopped. I went to the back seat and actually feel the air being suck into the vent. Kinda cool.

[NuShrike]

Also detailed a bit in our FAQ and in your owner's manual.

[Bonzocat]

I've had the same issue with the battery fan coming on. Funny thing is that it always happens in exactly the same place under the same conditions. Here's what happens. I drive down a fairly long hill (fully charging - perhaps overcharging - the battery.) I park the car for about and hour. When I get back in to drive up the hill again, the battery compartment fan kicks on. After a few minutes, the battery fan turns off.

I think I read somewhere that the batteries heat up if they're overcharged, so I'm guessing that's what's happening with my car.

However, today I had something strange happen. After the fan kicked in, as I was driving up the hill, the car started acting strangely. It was almost as if the transmission was slipping. Power was very uneven, and it took a half a second to a couple of seconds for power to kick in after I pushed down on the accelerator. I stopped, turned the car off, then started back up again. The symptoms improved, but only a little...that is until the battery fan turned off again. Then things seemed to return to normal.

Any thoughts out there? I'm thinking of taking the car in to the dealer, but I suspect they'll find nothing wrong.

Any suggestions would be appreciated.

Thanks!

[Sean05Opt6]

<div class='quotetop'>QUOTE(Bonzocat @ Apr 16 2006, 10:27 PM) [snapback]240745[/snapback]</div>

I've had the same issue with the battery fan coming on. Funny thing is that it always happens in exactly the same place under the same conditions. Here's what happens. I drive down a fairly long hill (fully charging - perhaps overcharging - the battery.) I park the car for about and hour. When I get back in to drive up the hill again, the battery compartment fan kicks on. After a few minutes, the battery fan turns off.

I think I read somewhere that the batteries heat up if they're overcharged, so I'm guessing that's what's happening with my car.

However, today I had something strange happen. After the fan kicked in, as I was driving up the hill, the car started acting strangely. It was almost as if the transmission was slipping. Power was very uneven, and it took a half a second to a couple of seconds for power to kick in after I pushed down on the accelerator. I stopped, turned the car off, then started back up again. The symptoms improved, but only a little...that is until the battery fan turned off again. Then things seemed to return to normal.

Any thoughts out there? I'm thinking of taking the car in to the dealer, but I suspect they'll find nothing wrong.

Any suggestions would be appreciated.

Thanks!
[/b]

Did you check the battery level at the time it was gutless?

I ask because I had a similar situation this past weekend.

I was driving through the Colorado Rocky mountains near the continental divide. I had 3 adults and gear for 2 days in the car and had been driving on VERY steep windy mountain roads for 4 hours. Basically, we were gaining 1 to 2 thousand feet in a short time only to loose it again on just as steep a grade on the way down. Then repeat.
After 4 hours of this my main battery fan came on for about 5 minutes.

Several times I found myself halfway up a mountain with depleted batteries coming into a short straight section of road and accelerating from 15 to 40. At these times the car reacted just as you described. Engine at high revs but no power. I assumed this was caused by the engine taking the entire load with no help from the electric motor.

Remember the engine is tiny but we are used to the car delivering a lot of torque when asked because of the partnership of gas and electric motors. I, for one, forget just how gutless the gas engine is by itself because I so rarely experience it in isolation.

BTW, the tank average for this trip was 52.7 MPG.

[Bonzocat]

Actually, it happened to me with a completely charged - possible over-charged - battery. I've heard somewhere (probably this forum) that the batteries can overheat when over-charged or excessively depleted, which would explain the battery compartment fan in both our cases. But could the overheating have something to do with the loss of power?

Today, I drove the same route on which I always get the battery fan to kick in. This time, on the way down the hill, I switched the car to Engine Braking, so the battery didn't over-charge on the way down. After sitting for the customary hour, I drove back up the hill and the fan didn't come on...so I guess that settles the fan question for me...

...but the loss of power questions is still a mystery. Anyone?


<div class='quotetop'>QUOTE(Sean05Opt6 @ Apr 23 2006, 08:35 PM) [snapback]244133[/snapback]</div>

Did you check the battery level at the time it was gutless?

I ask because I had a similar situation this past weekend.

I was driving through the Colorado Rocky mountains near the continental divide. I had 3 adults and gear for 2 days in the car and had been driving on VERY steep windy mountain roads for 4 hours. Basically, we were gaining 1 to 2 thousand feet in a short time only to loose it again on just as steep a grade on the way down. Then repeat.
After 4 hours of this my main battery fan came on for about 5 minutes.

Several times I found myself halfway up a mountain with depleted batteries coming into a short straight section of road and accelerating from 15 to 40. At these times the car reacted just as you described. Engine at high revs but no power. I assumed this was caused by the engine taking the entire load with no help from the electric motor.

Remember the engine is tiny but we are used to the car delivering a lot of torque when asked because of the partnership of gas and electric motors. I, for one, forget just how gutless the gas engine is by itself because I so rarely experience it in isolation.

BTW, the tank average for this trip was 52.7 MPG.
[/b]

[seasalsa]

The other night while I was driving my '05 Prius I noticed a hissing sound coming from the back seat of my car.

Thinking it was the sound system I turned the volume down. It still was hissing so I turned the sound system off. I looked back and noticed that the sound was coming directly from the battery vent.

I drove for about 5 more minutes and it stopped.

Is there a fan in the battery compartment that comes on? It sounded sort of like that. Just wondering if anyone else had experienced this.
[/quote]
Here is a photo of the battery vent system
[attachmentid=3310]quote name='vhmarx' post='239140' date='Apr 13 2006, 09:17 AM']

[qbee42]

<div class='quotetop'>QUOTE(seasalsa @ May 7 2006, 08:59 PM) [snapback]251227[/snapback]</div>

The other night while I was driving my '05 Prius I noticed a hissing sound coming from the back seat of my car.

Thinking it was the sound system I turned the volume down. It still was hissing so I turned the sound system off. I looked back and noticed that the sound was coming directly from the battery vent.

I drove for about 5 more minutes and it stopped.

Is there a fan in the battery compartment that comes on? It sounded sort of like that. Just wondering if anyone else had experienced this.

Here is a photo of the battery vent system
[attachmentid=3310]quote name='vhmarx' post='239140' date='Apr 13 2006, 09:17 AM']
[/b]

Yes, there is a fan in the battery compartment, which comes on as needed. Make sure nothing blocks the battery vent on the passenger side of the rear seat.

Tom

[Tempus]

Here's smaller version of the picture