HV battery fan Voltage vs. Temperature

Discussion in 'Gen 2 Prius Technical Discussion' started by 2009Prius, Jul 14, 2011.

  1. 2009Prius

    2009Prius A Wimpy DIYer

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    I have been wondering about the HV battery fan since I don't remember ever hearing it coming on. Finally looked at some logged data today: it must be way too quiet for me to hear but it does come on when the upper (highest?) HV battery temperature goes beyond 35C:
    HV battery fan V vs T  .gif
    HV battery fan V vs T.gif


    During this trip the temperature was below 35C and the fan did not turn on:
    HV battery fan V vs T .gif
     
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  2. uart

    uart Senior Member

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    Thanks for the info 2009Prius, I've been wonder at what temperature the fan kicks in.

    Now the other things I'd really like to know are what temperature it starts inhibiting EV mode (via EV button) and at what temperature it increases the battery fan to higher speed where you can hear it.

    From my observations with the EV button (standard equipment on British and Aussie models) it seems to inhibit EV mode at a lower temperature than that required for high speed fan operation. In other words, when it gets very hot here I usually notice that the EV button function goes out first (even while the fan is still only running slowly) and then if it gets even hotter the fan kicks up to a high speed where you can clearly hear it.

    In summer here the EV button goes out of service just about every afternoon, but only rarely do I hear the fan running fast.
     
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  3. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Ok, confirmed 35 deg C then. What is buC and blC?
     
  4. uart

    uart Senior Member

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    I'll have to let 2009Prius confirm, but I was reading them as Battery_Upper_Degrees_C and Battery_Lower_Degrees_C
     
  5. 2009Prius

    2009Prius A Wimpy DIYer

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    Yes. I inherited those somewhat strange names from the ScanGauge XGauge names which only allow 3 characters.
     
  6. 2009Prius

    2009Prius A Wimpy DIYer

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    In my area it just doesn't get hot enough. When it's hot and sunny out I sometimes move the car in the middle of the day to follow the shade and the EV button always works. Maybe you could set up your car to run PriiDash to do the measurements when it's hot in your area? I am sure people will thank you for your contribution to the collective knowledge. :)
     
  7. uart

    uart Senior Member

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    Yes it would be neat to monitor some of those variables, but currently I don't even have a scangauge or similar.

    Just from feeling the warmth of the outlet air flow (from the HV battery cooling duct) it doesn't seem to be super hot or anything when it starts denying EV. When I first noticed it happening (I mean when I first realized it was correlated with high temperatures) I was panicking a bit that my battery was toasting or something. But I'm guessing that they must be pretty conservative about it and it's probably only something like low 40's (C) where it goes into EV denial.

    It's also highly correlated with lots of regen, as in hills / mountains that push it up to 8 green bars. So that must definitely have an effect the battery temperature too. Unfortunately we've got a few biggish hills (smallish mountains) around here which often gets the battery charge max'ed out, and I also notice that the EV button function often goes out soon after that.
     
  8. Britprius

    Britprius Senior Member

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    I to find EV mode not available after coming down along hill (Whitcliffe Ludlow) with full green bars, the car then runs on battery only up to 40MPH until one green bar removed and then it will go into EV mode.
     
  9. andyprius

    andyprius Senior Member

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    You dids not seem to mention one very important criteria: Do you use the AC, at what setting? With a good cool air flow thru the HV Battery, do you still experience EV dropout? P.S.I have never heard my fan come on.
     
  10. uart

    uart Senior Member

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    Yeah I use the AC if it's uncomfortably hot. I get the loss of EV button function however even sometimes when it's only warm and not so hot that I need the A/C. Like I said previously the EV denial seems to happen even if the battery isn't all that hot. It definitely happens at a lower battery temperature than that required for the fan speed to increase to the level where it's easily audible.

    If you don't have the EV button then you wouldn't notice it. The car still performs well and will still run in full electric mode totally as per normal. The only real difference is that you cant use the button to force it into EV mode. I think it treats the EV mode button as a very non essential feature and therefore inhibits it at a relatively low temperature so as to try and prevent the battery temperature rising any further.

    Now at the next step, when it get really hots and the battery fan kicks into high speed mode where you can really hear it, then the effect on the cars performance is really noticeable and it really is very reluctant to run full electric mode or even to use the electric power as much as it should.

    Fortunately I hardly ever get to the heat level where the fan speed is high and the performance (other than just the EV button) is affected. Mind you my battery box could be a bit clogged with dog hair. I've cleaned my fan but I haven't gotten into the HV battery box yet. A recent poster here found that as well as having a clogged fan that he also had a fair bit of dog hair clogging up the battery modules as well. At the start of next summer I plan to access the battery housing and give it a clean up. Maybe I'll get better battery temperatures after that.

    Andy, you say you've never heard your fan running, but that doesn't meant it doesn't sometimes run. The fan is very quiet when it's running at low speed, and as 2009Prius has demonstrated it only requires a battery temperature of 35C (95F) to make the fan run. I'm sure you can get temperatures up around that level in Sacramento. Next time you've had the the car parked outside on a very hot day, try placing the car in ready mode and then going around to the back door and placing your ear next to the fan vent. There's a good chance that you will hear it whispering quietly away.
     
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  11. andyprius

    andyprius Senior Member

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    Thanks, I will have to try that, my situation is of course different, we do not have the tremendous humidity that you run into on the East coast and specifically Florida plus my car is mostly in my garage and cool. In summer I do start right out with AC on tho, set at about 75.I am curious as to why you would be so sparing with the AC tho, the health of the HV is most important. And, either way, with AC use or EV dropout the car will get lower mpg. You are absolutely correct that the EV mode button does not pertain to my 2005. Next year, with the PHV I will be on par with the other PC ers. OPPS.....All the above applies to Australia too. ( I think )
     
  12. 2009Prius

    2009Prius A Wimpy DIYer

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