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Thread: New Fan Fail relay

  1. #41
    Senior Member Bitsyncmaster's Avatar
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    I ran the same test with my external sensor attached to the cooler side (away from the power in pin "40 amps"). As expected that side did not heat very fast. The temp stabilized at 59 deg. C in the same 15 minuets. I was expecting this side to keep heating for a longer time.

    So my internal temp sensor is probably accurate with the designed value put back into my software.

    I ordered some thermally conductive potting epoxy and will post that result when I get one built with that. But I'm wondering if that will gain anything as far as better results. I'm guessing it will reduce the high side temp and increase the low side temp. So not sure what that buys me.
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  2. #42
    Senior Member DMC-81's Avatar
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    Hmm. I wonder if you can incorporate a mini Peltier plate (TEC- thermoelectric cooler) into the relay to keep temps down?

    https://www.kitsandsets.com/set-of-5...2v-200010.html

    (I'm just spitballing...not sure if this is a valid use of these or how long they last)
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
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  3. #43
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMC-81 View Post
    Hmm. I wonder if you can incorporate a mini Peltier plate (TEC- thermoelectric cooler) into the relay to keep temps down?

    https://www.kitsandsets.com/set-of-5...2v-200010.html

    (I'm just spitballing...not sure if this is a valid use of these or how long they last)
    I played with one of those when they first came out. It's just a heat pump (much less efficient than a compressor). Takes a lot of current to run it.

    I'm thinking my unit will be fine running that hot but remember most owners their OEM fans run 15 amps or less and low current fans run around 8 amps each.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #44
    Senior Member DMC-81's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    I played with one of those when they first came out. It's just a heat pump (much less efficient than a compressor). Takes a lot of current to run it.

    I'm thinking my unit will be fine running that hot but remember most owners their OEM fans run 15 amps or less and low current fans run around 8 amps each.
    Cool. Now Iím curious about what amperage my fans are running at. Iíll measure this weekend.
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

  5. #45
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by DMC-81 View Post
    Cool. Now Iím curious about what amperage my fans are running at. Iíll measure this weekend.

    It's a good thing to check. Best to use a clamp on DC current meter that you just clip over the jumper wire. Make sure your engine is running.

    FYI

    My friend had his fused jumper catch fire and I tested his fan current before I installed a set of low power fans. His fans each showed about 14 amps. of current but only one fused wire showed the damage.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #46
    Senior Member Bitsyncmaster's Avatar
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    I got my thermal conductive epoxy today. This epoxy has a filler and is really messy to prepare since you have to mix each jar (the filler settles). It's also much thicker than my T88 epoxy. Anyway I did get the center of a new unit filled with it and will fill the top of the unit tomorrow. Not sure if I can work with this stuff. It also cost twice what the T88 cost. I will try heating it to see if it works better filling the top.

    Anyway I was thinking maybe the T88 would be better since it keeps the high heat on one side and my one component rated at 85 C is on the cool side. My internal temp sensor is also on the cool side. I did keep the sensor set for 85 C.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  7. #47
    Senior Member Bitsyncmaster's Avatar
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    I poured the top side today with the new epoxy. I found heating the epoxy to 115 deg F made it thin enough to pour. It's still more work than the T88. My testing when it all hardens will convince me if I will use the new or old epoxy for production units.

    I could also add a metal plate on the hot side (heat sink) but I'm trying to keep my cost and build times down. I don't think the unit will overheat with normal fan currents without the heat sink.
    Dave M vin 03572
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  8. #48
    Senior Member Bitsyncmaster's Avatar
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    I'm still waiting for the new epoxy top to harden so I went back to the old epoxy unit and finished the testing on the cold side.

    At 40 amps, 20 amps each fan the cold side peaked at 59.8 deg. C.

    At 30 amps, 15 amps each fan the cold side peaked at 43.4 deg. C

    At 20 amps, 10 amps each fan the cold side peaked at 30.4 deg. C

    All those test are done at 70 deg F room temp so I'm guessing if your relay compartment is 100 deg. F then my test values would be 17 deg. C higher. So I'm guessing I would flash an over temp warning if your fans are drawing above 35 amps to 40 amps with the relay compartment covered.
    Last edited by Bitsyncmaster; 02-05-2018 at 07:18 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #49
    Senior Member Bitsyncmaster's Avatar
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    Ran the test on the new thermal conductive epoxy at 40 amps. As I expected the cold side temp was higher. It peaked at 73.7 deg C where as the old epoxy peaked at 59.8 deg C.

    So I expect the hot side testing will run cooler about the same difference.

    Now it did take longer to stabilize, taking 26 min. where as the old epoxy only took 19 min.

    I moved the sensor to the hot side and will test that later after the glue dries.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #50
    Senior Member Bitsyncmaster's Avatar
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    I ran the 40 amp test on the hot side with the new thermal conducting epoxy. To my surprise it ran just about as hot as the T88 epoxy test ran. The new test heat peaked at 90.9 deg. C and the old test it peaked at 91.0 deg. C.

    I don't know how to explain that result. Only thing I can think of is the thermal epoxy is less effective dissipating from the surface area to the air. Unless something in my testing introduced some error.

    So with that result I will use T88 epoxy in production units since that will keep may one 85 deg. C rated component cooler.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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