03 Auxiliary fan for HV battery

Discussion in 'Generation 1 Prius Discussion' started by rocketjones, Sep 18, 2018.

  1. rocketjones

    rocketjones New Member

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    I’m attempting to increase the cooling of my HV battery. I purchased a delta pfc0812de which operates around 3 amps. What can I splice into, to power my fan? I want it to run when the car is powered up.
    Thanks for any insight!
     
  2. mroberds

    mroberds Member

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    There is a white wire with a red stripe at the HV battery computer, which should have power when both the ignition key and "Ready" light are ON. It goes into pin 2 of the larger connector (B17).

    If it were me, I wouldn't try to run a new fan directly from this wire. I'd go get a 12 volt automotive relay, with a diode across the coil, and wire the relay coil (with correct polarity) between that wire and body ground. That way, the extra load on that wire is only about 100 milliamps (0.1 A), instead of the 3 A of the fan. The diode makes it so you don't spike the battery computer with 100 V+ when the relay turns off.

    Then, I'd come off of the positive terminal of the aux battery with my own fuse holder, put a 5 A or 10 A fuse in it, and continue to one side of the relay contact. The other side of the relay contact goes to your new fan motor, and then the other side of your new fan motor goes to body ground.
    Wrong car...? :)
     
  3. Brian in Tucson

    Brian in Tucson Active Member

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    In the trunk on the drivers side inner fender is a 12v HV cooling fan. You could tap into that wiring. With the low amperage of the fan you're putting in, a relay would be overkill imho. But then I think adding a HV cooling fan is kind of overkill anyhow. In the summer time when you might need more fan flow, you're just pumping more heat in from the already hot outside. If you ran a duct from the AC, maybe that might help.
     
  4. ChapmanF

    ChapmanF Senior Member

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    The fan that's there is speed-controlled by a pulse-modulating circuit. I am not sure how well it would work to add another fan on that same circuit, especially if the fan being added wasn't necessarily designed for a pulse-modulated supply.

    -Chap
     
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  5. TMR-JWAP

    TMR-JWAP Senior Member

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    I'm curious as to how you plan to "duct" this? Is this going to replace the OEM fan or operate in parallel with it? maybe set up to kick in at a certain threshold? What is it's discharge pressure and flow? Any idea what the OEM fan produces? Been a while since I've pulled a Gen1 Hv Battery, don't remember the exact setup of the battery and fan.
     
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  6. mroberds

    mroberds Member

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    The "New Car Features" manual (NCF182U) claims that the battery vent fan draws 60 W, and has three speeds. Low is 50 cubic meters per hour, medium is 100, and high is 150. This translates to about 29, 59, and 88 cfm respectively. It doesn't give any pressure or pressure-vs-flow information.

    OP's fan is rated at about 130 cfm with no back pressure, down to 0 cfm at 2 inches of water. The middle of the curve is about 70 cfm at about 1 inch of water.

    To Chap's point, the stock fan is on a 10 A fuse, and a 60 W motor would draw something between 4 and 5 A, depending on whether you use the 12 V nominal voltage, or the higher voltage when the aux battery is charging. If you wired the new fan in parallel with the existing one, you're adding 3 A to that, which the existing motor controller may or may not be able to handle. (That's why I suggested the relay.)

    Air from the passenger compartment is sucked in through two grilles in the middle of the rear parcel shelf (that look like small speaker grilles). There is a plastic duct under the parcel shelf that runs towards the passenger side of the car, turns and goes down the inside of the C-pillar, and then goes into the passenger end of the battery. On the driver's end of the battery, there is a big hole in the top of the case, with another plastic duct that goes up to the blower motor. The blower motor is on the inside of the driver's rear quarter panel - sort of the mirror image of the spot where the gas filler is on the passenger side. The blower motor exhausts either to the grille on the driver's C-pillar, or to a duct that runs down by the aux battery.
     
  7. rocketjones

    rocketjones New Member

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    I have removed the rear seat, all of the plastic trim and the top half of the intake duct. The fan will be mounted to the intake duct feeding cabin air to the battery. I don’t want to run the fan parallel to the stock fan as I believe it is controlled through voltage plus the delta pulls 40 watts max. The delta fan is pwm and controlled through frequency. I’m considering a toggle switch because I primarily will be using it when the car is started until I cool the cabin. The sun here in the south west is no joke. I covered the battery and the rear shelf with a mylar blanket.
     
  8. mroberds

    mroberds Member

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    If you go with the relay idea, you could put the switch in the ground side of the relay coil. In other words, you'd have a wire from the white/red stripe wire at the battery computer to the + side of the relay coil, and a wire from the - side of the relay coil, up to the front of the car, to one side of the toggle switch. The other side of the toggle switch goes to body ground under the dash somewhere - you don't need to run it to the back of the car.

    The advantage of doing this is that you only need to run one long wire from the back to the front. Also, the relay will automagically drop out if the car isn't READY or when you turn off the key, so you don't forget and leave the new fan running when you park the car. The disadvantage is that it's harder to use a lighted toggle switch if you do this.

    If you want to do it in the obvious way - +12 V to one side of toggle switch, other side of toggle switch to new fan, other side of new fan to ground - I would suggest using a Buss "add-a-fuse" or Littelfuse "add-a-circuit" fuseholder up front. You can get these at the car parts store and maybe even at the general store. This is a small fuse block with 2 spots for fuses, a plug that looks like the end of a fuse, and a lead wire. You unplug one of the fuses from the Prius fuse block and plug it into the new fuse block, then plug the entire new fuse block into the spot where that fuse was. Then, you plug a new fuse for your new circuit into the other spot in the new fuse block, and connect the lead wire to your new circuit. (Follow the instructions - if you get it the wrong way around, the existing fuse has to carry all of the current for your new circuit as well, which is probably not what you want.) Pick a fuse that only has power when the key is on, so you don't accidentally leave the new fan running when you park the car.

    For mounting the toggle switch up front, there are a couple of "blank" switch plates around and under the power mirror switch and dash light dimmer. I haven't tried it on a Prius, but on other cars, you can often remove one of the blank plates, drill a hole in it, install a "generic" toggle switch in the plate, and then put the whole thing back in the dash. If you want it to look really slick, put one of the blank plates off of your car in your pocket (for comparison) and hit up the you-pull-it junkyard, looking for any late 90s-early 00s Toyota or Lexus - especially the higher-trim models with more options. You will probably be able to find a switch that will fit right into the spot where one of the blank plates on your Prius is. Make sure the switch is a toggle or push-on, push-off, instead of a momentary - at the junkyards I've been to, it's OK to bring in a multimeter to test this out. Also cut the connector for that switch, plus as much wire for it as you can get, out of the wiring harness of the junker - it will be hard to find a matching connector anywhere other than the dealership. The local car stereo and alarm shop (an independent place - not Worst Buy) might also have a switch that will plug into a stock switch location on a Toyota - asking is free.
     
  9. rocketjones

    rocketjones New Member

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    Super late reply, mroberds thank you so much for your wisdom! I'm about to get into my second summer in the southwest and I haven't completed this project, although I have replaced shocks/struts and top mounts plus a corolla front bar!
    What I gather is I can wire in power from the fuse box with a corresponding fuse probably anything below 10 amps. My question is, should I add in a relay between my toggle and fan to control the operation? I would of course add in a lower amp fuse close to the fan. Please correct me if i'm wrong.
    Thanks so much! Again!
     
  10. Brian in Tucson

    Brian in Tucson Active Member

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    Super late response. I wouldn't bother. I live in a place where 110 in summer is possible, 105 is common. The battery box seems to keep up with the heat, just fine. With the stock fan system. Toyota engineered all this in, and the car was offered in place that got really quite hot.
     
  11. 2002_Pri_Rod

    2002_Pri_Rod Member

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    I am interested in more information about the Corolla front bar - did this remove some of the sway? What year Toyota? Seems like a big job but I am looking at any updates I can find to remove the body sway and improve cornering - I have made a lot of improvements but...
    thanks in advance
     
    #11 2002_Pri_Rod, Apr 22, 2019
    Last edited by a moderator: Apr 22, 2019
  12. rocketjones

    rocketjones New Member

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    The bar is from a 2003 Corolla, I picked it from a Mexican junkyard for $20. The front end feels more level going around curves. The outside wheel doesn't dive the way it did before, the whole front of the car stays more level and you can feel the tires doing more work. I also replaced the end links with something more robust, MEVOTECH TXK80230. Eventually I will do poly bushings.
     
  13. 2002_Pri_Rod

    2002_Pri_Rod Member

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    Thanks for the reply - very interesting - So how long did it take to swap the sway bar in? I will get under mine soon to assess how big of a job this looks like to me
     
  14. rocketjones

    rocketjones New Member

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    There's a write up on these forums. Jack up the front end of the car, take off a front wheel or both, loosen the subframe, disconnect the dogbone, disconnect end links, disconnect the sway bar bushings, pull out old bar and install new bar, lube up new bushings and reconnect and torque everything to spec. It's pretty straight forward. Take your time and it's maybe an hour to an hour and a half job. Before you start check your endlinks, mine were toast and needed replaced.
     
  15. 2002_Pri_Rod

    2002_Pri_Rod Member

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    Great - thanks - I jacked the car up the other day and looked - job does look fairly straightforward - thanks for the confirmation
     
  16. dabard051

    dabard051 Tinkerer-in-Charge

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    RocketJones, do the MevoTech endlinks make that big a difference in handling and durability? I know the endlink bushings on my Prius are good for only 2-4 years, but they're easy to replace when doing a brake inspection.
     
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