Sometimes I hear a fan noise coming from the grill on the right rear passenger's seat. I'm guessing this is for the battery pack when it gets too hot? And on a semi-related note, how would one know if their battery isn't holding a charge well? I'm at about 19,000 miles and the battery seems to drain quicker than 9,000 miles ago. Paul
Yes, that fan means that the battery system (the battery control electronics are back there also) is getting warmer than it wants to be. If you are driving around in hot weather with the A/C off, thinking that this somehow does the car a favor, don't: it does not. The battery system gets its cooling air from the cabin through the aforementioned vent; if you are too warm then the battery is also too warm. Roll up the windows and turn on the A/C. Concerning bad cells in a battery, someone else will have to comment.
<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 04:50 PM) [snapback]463097[/snapback]</div> Highly unlikely. It's more likely that it's a difference in outside temperature or some other external factor. The Prius has good diagnostics built in, and will let you know if you are having any sort of battery problems. Tom
<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 01:50 PM) [snapback]463097[/snapback]</div> The A/C runs off the HV battery so your battery will drain faster with the A/C on.
<div class='quotetop'>QUOTE(Tideland Prius @ Jun 16 2007, 05:06 PM) [snapback]463177[/snapback]</div> I should probably mention that the AC was off and the windows were down. PK
<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 05:51 PM) [snapback]463182[/snapback]</div> You did not mention what the outside temperature was. Whatever it was it was too hot for the battery to be comfortable so it turned the fan on. Do your battery a favor, close the windowss and turn on the AC. It will mean about only about 1 or 2 MPG difference. True the AC runs off the HV battery but that just means that your car won't overheat like most with the AC on.
<div class='quotetop'>QUOTE(seasalsa @ Jun 16 2007, 07:12 PM) [snapback]463222[/snapback]</div> It was maybe 80-90 outside. So it would be better to use the AC. and keep the cabin temp down? Since of course, the fan is only moving air, and not really cooling down the battery.
<div class='quotetop'>QUOTE(pkhoury @ Jun 17 2007, 03:22 PM) [snapback]463538[/snapback]</div> Yes, close the windows and use the A/C. When the A/C is on the fan will run at its usual low quiet speed (except possibly for a short time after you first get in, because the whole car may be hot from the Sun).
<div class='quotetop'>QUOTE(richard schumacher @ Jun 17 2007, 05:14 PM) [snapback]463652[/snapback]</div> I'm surprised they never mention this in the manual.
<div class='quotetop'>QUOTE(pkhoury @ Jun 17 2007, 01:22 PM) [snapback]463538[/snapback]</div> Yes. The Prius supplies conditioned air from the cabin as thermal management for cooling the batteries. Outside air is conditioned (heated or cooled) by the vehicle’s thermal comfort system to a level comfortable for the driver. This approach has the advantage of providing air that is not only comfortable to the passenger(s), but also ideal for use in heating or cooling the battery. The Prius has a computer that’s solely dedicated to keeping the Prius battery at the optimum temperature and optimum charge level. Both these functions maintain the long life of the battery.
<div class='quotetop'>QUOTE(pkhoury @ Jun 17 2007, 07:24 PM) [snapback]463657[/snapback]</div> I agree, it ought to point this out. Perhaps it never occured to Japanese design engineers and manual writers that someone would choose to drive around with the windows down sweating like a pig hoping to save a few teaspoons of fuel :_>. But we already know that the Prius owner's manual is not perfect; for another example, it *still* implies that one must add 3.9 quarts of oil during a change, which, assuming that the marks on the dipstick are accurate, is about 0.4 quarts too much/about 0.9 quarts more than necessary.
I have never heard the battery cooling fan. Is it noticeable, or would someone have to be sitting near the vent to hear it? (Just want to make sure that it works)
<div class='quotetop'>QUOTE(8AA @ Jun 18 2007, 05:16 PM) [snapback]464371[/snapback]</div> It is a variable speed fan and you seldom hear it unless the battery is really uncomfortable and the fan goes to the highest speed.
<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 02:50 PM) [snapback]463097[/snapback]</div> We've been getting close to 100 here in Albuquerque lately, and my mpg has dropped from 56/tank to 53, so I'd say a 3 mpg hit. Also traction battery will go down much faster with AC on when its that hot, and I keep the AC on 80 degrees-- I suppose due to the electric AC compressor running and maybe also the battery is less efficient at higher temps, I hit 100% ICE condition much more commonly lately. A Question for the gurus... Is it better to have recirc off so that outside air pressurizes the cabin and more goes into the battery vent? When I looked at the 12 volt battery under the trunk floor, looks like that's where the traction battery vent exhaust goes, not sure if it goes outside the cabin. If it just exhausts under trunk floor, would not matter if outside air was on or off.
<div class='quotetop'>QUOTE(abq sfr @ Jun 22 2007, 11:33 AM) [snapback]466461[/snapback]</div> Attached is a cutaway of the battery vent system. It exausts out the right rear wheel well. If you use Auto/AC set at 80 degrees the computer will take care of where the air comes from.
