battery cooling fan mod

Discussion in 'Gen 3 Prius Technical Discussion' started by NiHaoMike, May 19, 2012.

  1. NiHaoMike

    NiHaoMike Member

    Joined:
    May 6, 2012
    98
    16
    0
    Location:
    San Diego, CA
    Vehicle:
    2011 Prius
    Model:
    Four
    Prius OEM fan control - EAA-PHEV
    It seems like at least in the Gen II, the battery fan is quite "lazy" and comes on way too late just like most variable speed fans in electronic equipment.

    In the Gen III, does the fan have the same problem? If so, is there an easy way to perform the mod that can be easily undone?
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    87,553
    38,971
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    might be a good idea in warmer climates, driving with a/c on and fan running might extend battery life.
     
  3. Rebound

    Rebound Senior Member

    Joined:
    Mar 11, 2010
    3,697
    2,284
    0
    Location:
    Portland, OR
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    The most important thing is to check the fan and make sure it's clean. There's no filter to keep gunk out.
     
  4. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,036
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    What makes you think that the designers of variable speed fan controls do a poor job optimizing? Is there some secret that you are not sharing with the rest of the engineering world?

    Tom
     
    dbcassidy and secondspassed like this.
  5. NiHaoMike

    NiHaoMike Member

    Joined:
    May 6, 2012
    98
    16
    0
    Location:
    San Diego, CA
    Vehicle:
    2011 Prius
    Model:
    Four
    Just about every variable speed fan I have seen is on the "lazy" side in that they let the devices being cooled run near the maximum operating temperature. In particular, some Antec power supplies have a "hot varnish" smell when under load. I also got to replace the caps in many of these and rewire the fan for full speed at all times. They're probably optimizing it to fail just outside warranty...
     
  6. macman408

    macman408 Electron Guidance Counselor

    Joined:
    Mar 21, 2010
    1,179
    356
    1
    Location:
    California
    Vehicle:
    2010 Prius
    Model:
    V
    Typically, they're optimizing for low noise, because when in the presence of a whiny fan, some of the whine is transmitted to people, which greatly amplify the whining.

    There are a lot of problems that variable speed fans can have; for example, alternating between two speeds causing many thermal cycles when generating too much heat to stay in the lower speed, and too little to stay in the higher speed. This causes repeated mechanical stress as parts expand and contract, and can eventually cause failure.

    That said, I'm not entirely sure what the triggers are for the fan in the Prius. Watching one of the battery temperature sensors once, the temperature was staying steady; not a degree up or down. The fan had gone to a relatively high speed, and then back down, without the temperature changing much. It may be that they've characterized the heat production of the battery at various SoCs and currents, and then preemptively cool it when you're, for example, charging many amps at high SoC. Or it may be that they're using a different temperature sensor than the one I'm looking at, which is closer to where the heat is being produced, and/or attached to a smaller mass.

    In general though, I think it's probably a pretty well-designed system - I've heard that it's actually running quite a bit more than you'd think, it's just so quiet through about the first 6 fan speeds that you can't tell it's running without a gauge of some sort.
     
  7. JohnCleary

    JohnCleary Junior Member

    Joined:
    Feb 12, 2012
    15
    0
    0
    Location:
    SoCal
    Vehicle:
    2010 Prius
    Model:
    II
    How do you get access to the fan, does the cover come off?
     
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    87,553
    38,971
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    you cans earch for a thread with pics that explains everything.
     
  9. vincent1449p

    vincent1449p Active Member

    Joined:
    May 24, 2004
    894
    330
    0
    Location:
    Singapore
    Vehicle:
    2012 Prius c
    The fan is optimized to run at the most efficient speed depending on the HV Battery temperatures. If you really want to manually control the fan speed, you can do it easily without cutting any wires:

    1) Techstream with J2534 interface
    2) ScangaugeII with Xgauge
    3) Torque with ELM327 ( BT or USB )

    Vincent
     
  10. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,036
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    Exactly. There is a balance between noise and cooling, otherwise most systems would use single speed fans. Of course with big fans there is also an energy issue that comes into play.

    The Prius is optimized to protect the HV battery. There is no reason to believe that the fan needs to run at a faster setting. Dog hair, on the other hand, can be a problem.

    As for what triggers the battery fan in a Prius: it's the battery temperature.

    Tom
     
  11. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,516
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    I have noticed that auto AC in my high desert climate often turns to recirc. I have taken to setting the AC with manual non-recirc mode on the premise more cooled ventilation will reach the HV battery.

    Make sense ? When I finally get around to installing the app torque, I'll monitor HV battery temps in both AC modes to actually see what differences are present. I've become a big fan [sic] of mothering the HV battery temps.
     
  12. 2009Prius

    2009Prius A Wimpy DIYer

    Joined:
    Mar 25, 2009
    2,702
    480
    63
    Location:
    USA
    Vehicle:
    2009 Prius
    Here are some data recorded from my gen 2 Prius (US model 2009):

    [​IMG]

    [​IMG]

    [​IMG]

    It looks like the HV battery cooling fan starts to turn on when the HV battery temperature is around 35C. During a record high temperature trip (under my climate and driving conditions) the HV battery temperature was kept under 45C with less than 10 V on the HV battery cooling fan (the fan was not maxed out yet).

    Also see this thread:
    http://priuschat.com/forums/gen-ii-...08-hv-battery-fan-voltage-vs-temperature.html
     
    1 person likes this.
  13. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    5,131
    1,305
    0
    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
    I have been monitoring my battery fan and temperatures for a while now, especially now that temps in NC have begun to get in the 80's. I posted some results under the thread 2010 Scan Gauge Work.

    What I have seen agrees with 2009Prius but I monitor the battery fan mode rather than voltage. There are 6 modes which are set speeds.

    The system appears to be smarter than just based on battery temperature. It also seems to set speeds based on OAT and whether the AC is on or off.

    It appears that the basic is beginning at 95F (35C) that it increases fan mode or speed for each 5F increase. But I have seen the battery fan mode at 4 with as little as 105F and have also seen a battery fan mode of 1 at 114F on a cool day.

    The battery temps here range from 90F in the mornings and up to about 110F depending on how much start/stop driving I do versus highway driving.

    I have noticed that the battery temps rise quickly and drop very slowly. At nights when I park the car the temps are usually in the 110F range and overnight they only drop to about 90F even with the OAT in the 60's.

    Even at a mode of 4 neither my wife nor I can hear the fan running unless we put our ear right up to the rear vent.
     
    1 person likes this.
  14. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    87,553
    38,971
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    my 08 did the same thing with recirc. i always ran manual, temp low and a/c either on or off. if a/c off i'd want fresh air. if a/c on, i'd want cooled (recirc) air. but the manual always says to shut off recirc after the car cools down. some mfgs. call it max a/c . maybe it's so you don't keep breathing the same air?
     
  15. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    5,131
    1,305
    0
    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
    I have not watched recirc versus non-recirc that closely, but one thing that I did notice that surprised me was that the cooling with convection only (battery fan not running) was not that good. The battery air flow temp would only be about 2-3 degrees below battery temps, regardless of cabin temp. Once the fan came on in just Mode 1 the battery air flow temp would drop almost immediately to about 2-3 degrees above cabin temp.

    Depending on outside temps and cabin temps with just vent airflow the battery temps would stay fairly constant or at least not increase very much. With the AC on the battery temps would eventually begin to decrease. Of course this all depends on how much start/start driving you are doing during this time.

    I will have to start watching recirc versus non-recirc to see if I notice any appreciable differences.
     
  16. kithmo

    kithmo Couch Potato

    Joined:
    Apr 25, 2010
    2,291
    2,589
    47
    Location:
    South Yorkshire, UK
    Vehicle:
    2016 Prius
    As you say, you're cooler with recirc on, which is better for the HV battery in hot climates. With the Gen 3, you won't be breathing the same air though as the Gen 3 Prius allows some fresh air in with recirc on. IIRC, the only time it shuts off the outside air altogether is when you press the "Pollen removal mode" button.
     
  17. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,036
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    This is also the default mode for the Gen II. The Gen II always allows some outside air, even in recirc. If desired, the dealer can override this with a Techstream tool.

    Tom
     
  18. SamM

    SamM Junior Member

    Joined:
    Mar 25, 2014
    28
    8
    0
    Vehicle:
    2004 Prius
    When taking apart the hv battery and accompanying ductwork, we find there are three thermistors attached to various parts of the battery pack and a sensor of some sort in the outflow duct leaving the pack (at higher temp) on the way to outside the car. This sensor has ribbed heat sinks on it and is near the R rear passenger side. This sensor is heated electrically and also has the warm outflow air from the battery blowing over it. Anyone know what that is and why it's heated? It gets almost too hot to touch if air is not flowing over it and cooling it and I've examined them on multiple cars and it is working properly. Thanks!
     
  19. macman408

    macman408 Electron Guidance Counselor

    Joined:
    Mar 21, 2010
    1,179
    356
    1
    Location:
    California
    Vehicle:
    2010 Prius
    Model:
    V
    Probably an airflow sensor; heating it allows the determination of how fast air is moving past the heatsink. Without heating, all you'd know is the temperature of the outgoing air.
     
  20. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    5,131
    1,305
    0
    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
Loading...