Traction battery fan

Discussion in 'Gen 3 Prius Technical Discussion' started by yeldogt, Mar 23, 2012.

  1. cobradb

    cobradb Member

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    never heard my 2010 batt fan
    and what is the large vent that goes into the spare area? it appears to be the fan vent out.
     
  2. jdcollins5

    jdcollins5 Senior Member

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    The large vent is the opening for cabin air to be pulled with the battery fan that we have been discussing in order to cool your HV battery. You need to be sure to keep this open and clean. You also need to keep the cabin cool not only for your comfort but for your HV battery.

    You should not hear the battery fan unless it is unusually hot or you are doing a lot of stop and start driving and using a lot EV mode. I had to force my fan up to top speed in Mode 6 before I could really hear the fan.
     
  3. jdcollins5

    jdcollins5 Senior Member

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    With the temps getting up in the mid-80's I have had plenty of opportunity to monitor the battery fan. I have found out some interesting features of the battery fan:

    1) Toyota does a good job of maintaining temperature on the HV battery. The battery fan control is much more complex than just running the battery fan speed based on a set temperature.
    2) I have seen the Battery Fan Mode (BMF) at 1 with battery temperatures (B2F) as low as 96F and as high as 115F. The first was with ambient temps around 85F and the second with ambient temps at 60F. So the controls definitely seem to use the ambient temp sensor for an input. The controls also seem to use the cabin temp as an input also.
    3) Without the battery fan running the battery inlet air temperature (BtT) is only 2-3F above the battery temp (B2F), even with AC and cabin temp in the high 70's. Once the battery mode goes to 1 the BtT drops quickly to about 2-3F above the cabin temp and the battery temp (B2F) begins to gradually decrease. So the batteries need the fan to run in order to pull cabin air through the batteries. The natural draft without the fan is fairly minimal.
    4) If the ambient temp is high, 85F for example, the battery speed mode continues to increase as the battery temp increases above 100F, to as high as Mode 4 with the battery temp at 105-110F.
    5) If the ambient temp is cool, 60F for example, the battery speed mode remains in Mode 1 even with battery temps as high as 115F.
    6) So, like the Climate Control system, the battery temperature controls seems to have more complex logic than just speed versus temperature.
    7) The battery fan runs much more than we think since we cannot hear it unless it gets up to almost max speed.
     
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  4. spiderman

    spiderman wretched

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    Interesting observations JD. Now you just need to plug the vent and let us know what happens. ;)

    Wouldn't think that they would completely rely on the fan to move the air... seems like a weak spot should the fan fail.
     
  5. GreenJuice

    GreenJuice Active Member

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    Great job! Ambient temp may be reported incorrectly in certain conditions of grill blocking, so I guess this may have an unintended consequence.

    Also, useful to know about the silent running as another source of energy use. I wonder if it is too low to register a change in the background level of battery current gauge (BtA) when the fan modes go from 0 to 4?
     
  6. Former Member 68813

    Former Member 68813 Senior Member

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    Interesting. One thing I noticed that sometimes I hear some wind activity near the vent while driving ~40 mph, but it disappears when I stop driving.
    I thought it was wind noise transmitted/resonating in the fan duct.

    Could fan speed also depend on speed of driving.
     
  7. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I put filter material behind the intake grill for the battery fan, about a year back. It is coarse material, actually a replacement filter for one of our vacuum cleaners.

    I checked it recently and it had collected a bit of dust, which I blew out. It's got to be reducing air flow slightly, but seems ok so far.
     
  8. yeldogt

    yeldogt Active Member

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    The sound that I hear is the fan - and in increases the more I drive in the 30 - 40 mph range -- it will start to slow down if i coast.

    At higher speeds I don't hear it and but the time the car gets below 10 mph the fan is quiet
     
  9. andyprius

    andyprius Senior Member

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    I'm lost now, where are we reading or just deciding that the car is in different modes, of cooling fan? :(
     
  10. macman408

    macman408 Electron Guidance Counselor

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    I assume you mean without the fan running, it's 2-3F *below* the battery temp? Or is it really higher in the battery inlet than the battery itself?

    I agree, it's a less than perfect design. What's the threshold for throwing some sort of user-visible warning? And can it do so just from a fan malfunction (e.g. is there a tach on the fan to ensure that it's running at the requested speed)? I guess at some temperature, it just avoids using the battery; several members have reported that condition (though due to heavy use and high temperatures, not fan failure).

    I used to design computer boards for telecommunications, which would be sold to other companies who would put our boards along with others inside a case, add a power supply and fans, etc. Our company once got a return from one of these customers where a number of inductors and other components had melted the solder holding them to the board, then slid down the board with gravity. It turns out that their cooling system had failed, and there was no path for convection to carry air out; the fans blew cold air in the bottom of the case, up one set of computer boards, over a piece separating the front and back of the case, back down through the back of the case over another set of boards, and hot air exited at the bottom in the back. So when the fans failed, it turned into an oven. Given that the solder melted, the temperature was at least 185°C/365°F (though since solder conducts heat away from hot components, the air temperature was probably somewhat less than that).

    That said, there is a convective path out of the battery, I believe; as hot air rises, it should come out of the battery air inlet! That's not exactly fantastic design, since the fan has to work against that (especially at low fan speeds), but given the space restrictions and a likely desire to not have a battery vent visible on the side of the car, there aren't many other options. But that explains why the air inlet gets so hot; the airflow direction reverses when the fan is off.
     
  11. jdcollins5

    jdcollins5 Senior Member

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    You are correct, the battery fan inlet air temp is 2-3F below battery temp and not above. Thanks
     
  12. jdcollins5

    jdcollins5 Senior Member

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  13. jdcollins5

    jdcollins5 Senior Member

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    The Repair Manual lists DTC's for temperature sensors being out of range but does not say what it does other than throwing the DTC's. It does have both battery fan speed and voltage sensors. If either the fan speed or voltage is out of range it will throw a DTC. So there are some protection DTC's to give us warnings of malfunctions.

    Yes, I was surprised that the convective air flow did not lower the battery fan inlet temperature any more than it did, even with the AC on. But when the fan came on even at the lowest speed of Mode I the inlet temp fell quickly to just above cabin temp. So it does depend on the fan but at least it gives out some DTC's if it senses any issues.

    I am going to have to block the vent as spiderman requested and see what happens.
     
  14. prominence

    prominence Junior Member

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    Hi everyone.

    I just searched and came upon this thread because this happened to me for the first time today and I got a little scared about it.

    Was merging onto a highway, at the top of eco bar nice and steady (wasn't gunning it by any means), and noticed a noise that sounded like a window was open, coming from the back. I definitely pinpointed it coming from the rear passenger side, and no windows were down, so it was coming from the vent area. Once I was merged onto the highway, it lasted for a good 5-10 minutes.

    I have a 2011 with only 10,200 miles on it. First time I've ever heard the fan. Wondering if I should be worried, or just keep chugging along. (I do play the radio loudly often, so it may have happened before, but this was the first time I "noticed" it because I was on a bluetooth phone call at the time so radio was off).

    I bought this car in Sept 2011 so it's just now getting it's first "real world driving exposure" to temps 60-70+. It was 73 degrees outside at the time of this happening.

    Any thoughts? I don't know if I should get it checked out or not, but can I just assume it's fine as long as no error lights come on or anything? The air conditioner was on, flow air from outside, and I never have pets or passengers in the car (I'm single and live alone, rarely have passengers). I rarely have windows down, usually just use A/C. Windows all tinted at 20% (pretty dark) so the interior temp was not hot or anything.
     
  15. jdcollins5

    jdcollins5 Senior Member

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    As long as you do not see any warning lights or fault codes and the car runs normally I would not worry about it. The car does a very good job of taking care of itself.
     
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  16. Alex777

    Alex777 New Member

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    Hi everyone.
    I just bought new 2012 prius.
    And one evening i left my windows slightly open so that way all of the heat could evaporate.
    Anyways the long story short, i forgot to roll up my windows and went to bed. On the next day it wasn't raining but it was very foggy and i noticed that bunch of water droplets fell right into cooling air duct on the right side, rear seat for HV cooling fan. Then while i was driving i noticed some weird smell, like a rotten eggs or something. I'm pretty sure that not much water went in there although my side doors were pretty wet just like whole car outside.
    Anyways, do you guys think it could be a big problem? or i should just not worry about it at all? I think it got about 150mL of water in there which is not even a half of a regular 500mL water bottle.
     
  17. Jeanette

    Jeanette New Member

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    I have the same problem...just bought this Prius new a couple of months ago, and I hear the sound of a rush of air- NOT a fan noise- whenever I drive at about 40 or faster. The outside temperature makes no difference, neither does changing the air conditioning settings. It sounds like the window or the door is not closed properly. It's making me nuts. I hope it's a normal thing. I'm debating calling the dealership to see if they have any insights.
     
  18. I have never had a problem on my 05 nor now on my PIP, I always started the car with the windows open or on Full AC autoo, then within 2-3 blocks adjust to my comforTable temperature . I did take all the plastic piping off and check for cleanliness after about 4 yrs of ownership. The biggest problem is dog hair, not using AC &/or working the car too hard going up mountain ranges.
     
  19. Sergio-PL

    Sergio-PL Member

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    I've heard fan few times (5800 miles on the clock). Most of the time it happens after hard acceleration in eco mode (like flooring for 3-5 seconds few times in a row when switching lanes). It works for few minutes. Then sound disappears.
    One or two times it just turned on without any particular reason to do so but there may be a lot of conditions, maybe even simple self test. This car makes a lot of sounds without any "normal" reason, so why not self check of the fan.

    macman408 if fan fails or get clodged and battery temp will go outside operating range car will refuse to use it (like while driving below freezing, when engine powers the car even at S0 state). So from the car point of view battery is safe. Probably PIP, Alpha/Plus have better safety management due to higher risk while using Li-Ion or Li-Po chemistry.
     
  20. That is interesting, I had my rear bumper off on my 05 to repair some damage. With the sides exposed, you should see two very light and sensitive squarish panels. These are obviously to aid outflow of air, (HV cooling air) As air flow itself or the generator of air flow makes noise. I would not worry about it unless the sounds really get loud or even more important, you note any extreme temperature difference coming out of the fan, That temperature is easily monitored. Stick a thermometer in the duct!
     
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