I just rebuilt my Gen 2 hybrid battery and I crushed the temp sensor.

Discussion in 'Gen 2 Prius Main Forum' started by derekc, Apr 4, 2018.

  1. derekc

    derekc Junior Member

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    I just rebuilt my Gen 2 hybrid battery and I crushed one of the 3 temp sensors. There is a thermistor in there that I need to replace. I know I can replace the whole wiring harness but if I can find the right thermistor, it will be cheaper and save me from taking the cells apart.

    This link tells about the thermistor:
    http://www.justanswer.com/uploads/skyvisions/2008-06-21_094242_05_prius3.pdf

    And this tells it needs to be at 10k ohm at 25C:

    [​IMG]
    Would a "standard" 10K ohm thermistor be a suitable replacement?
     
  2. JC91006

    JC91006 Senior Member

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    You can probably trade that part with a shop that buys new Toyota batteries. Every one they buy, they have to return a core with that part on it
     
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  3. Dxta

    Dxta Senior Member

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    I think you could use it
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    So what happens when you have a cold morning or a very hot afternoon and there's a 50+ degree difference between temperature indications?

    Did you actually damage the sensor or just break the clip? Pretty hard to actually damage the sensor.
    If just the clip then just use some rubber cement to mount it in place, or you can do what I've seen in a couple Dorman batteries and just let it lay in the bottom plenum.

    My mistake, thought you were referencing just using a 10k resistor
     
  5. ericbecky

    ericbecky Hybrid Battery Hero

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    Sometimes if it is just laying in the bottom plenum I see the temp difference between the different sensors make the Prius throw an error code.
     
  6. derekc

    derekc Junior Member

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    This is the sensor that is broken because of too much "handling":

    [​IMG]

    It has just a thermistor (a resistor that changes depending on the surrounding temperature).
    Instead of changing the whole wiring harness which requires taking the cells apart, I want to splice in a new thermistor.

    According to http://www.justanswer.com/uploads/skyvisions/2008-06-21_094242_05_prius3.pdf,
    it is resistance is 10K at 25C and according to the description, resistance goes down when temperature goes up so it is a NTC thermistor:

    [​IMG]

    I need to ID the thermistor in order to find a replacement (to just replace it, not the whole wire harness).
    I was wondering if anyone has done this and know what specs I need for the thermistor.

    Thank you.
     
  7. derekc

    derekc Junior Member

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    About to get this:

    [​IMG]


    But not 100% sure it will match up the temp-resistance graph.
     
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    If you prefer to have the correct one, just message me through the 'start a conversation' link and give me your address. I'm sure I can find a damaged harness in the shop and can cut one off with some lead on it. I can't provide same day delivery like amazon, but I can have it in the mail tomorrow.
     
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  9. TMR-JWAP

    TMR-JWAP Senior Member

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    here's a chart for the amazon thermistor. It looks to be fairly close........
     

    Attached Files:

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  10. derekc

    derekc Junior Member

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    Yes, Amazon same day delivery is amazing. I just got it and I did some resistance test in ice and hot water. It looked good and I have just finished installing it into the battery:

    [​IMG]

    [​IMG]

    [​IMG]

    And installed the battery pack into the car. No death of triangle and techstream looks good:

    [​IMG]

    I will let it idle in my garage this evening while running the heat. If everything is ok, I will button everything up tomorrow.

    So, guys, if your temp sensor is damaged or defective somehow, no need to replace the whole wiring harness, replacing the thermistor should work.
     
    #10 derekc, Apr 5, 2018
    Last edited: Apr 5, 2018
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  11. TMR-JWAP

    TMR-JWAP Senior Member

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    well done! For some reason, I was expecting solder and heat shrink..................always forget about the handy/dandy splices. Showing my age I guess............
     
  12. Bob k

    Bob k New Member

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    Getting ready to finally take this on; question: is the transistor-y-looking thing (see red arrow) part of the process (and how/where) or am I just splicing together the wires, as per the pictures in this thread?
     

    Attached Files:

  13. Dxta

    Dxta Senior Member

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    That's a resistor. What's the rating on it.
     
  14. floridagreg

    floridagreg Junior Member

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    Hey everybody
    New to the forum
    I was just wondering also to this thread
    as i have the exact same problem at the end of my lower temperature wires under the traction battery (the thermistor?)on my06 prius
    I noticed the question wasnt answered about the resistor that comes with the repair kit bought thru amazon
    Do i need to install the resistor as well?
    Any help would be greatly appreciated
    Thanks greg
     
  15. Joe Hull

    Joe Hull New Member

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    I have a similar problem, the sensor broke off with no wire left on it to reconnect. Can I just search for 3950 thermistor on Amazon? I found several, will any of them work?
    I appreciate any direction you can give.
     
  16. LoveourPrius

    LoveourPrius Junior Member

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    Rather than replace the half dozen cells in my 2006 Prius HV battery, I decided to replace all the cells from a good battery out of a 2011 Prius. When removing the cells from mu 2006 battery I discovered that the middle 1 of 3 temperature sensors had melted and had damaged the cell next to it. The other temp sensors clipped to cells 1 and 28 appear to be okay.

    1) Is it normal for the middle temperature sensor to be inserted (jammed) between 2 cells (#14 and #15) rather than clipped to the bottom of a cell?
    2) Are 2011 Prius temperature sensors compatible or the same as the 2006 Prius?

    The car has been excellent since I purchased it in 2008 so I'd really like to keep it on the road.

    Thanks,
    Gerry
     
  17. TMR-JWAP

    TMR-JWAP Senior Member

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    1....absolutely not normal. All three temp sensors should be clipped to the bottom of a module in the appropriate recess. There should also be 2 extra clips under there holding the wires in place. There should NEVER be one mashed between 2 modules. perhaps this was a previously rebuilt battery?

    2....I'm not 100% certain whether the Gen 2 and Gen 3 thermistors share the same temperature characteristics or not. I do know the Gen 3s slip into the top of a module instead of clip onto the bottom. In that aspect, they are mechanically different and can't interchange due to their physical shape.

    3..I'm still trying to wrap my head around this to understand how it could even happen...any photos? I discovered that the middle 1 of 3 temperature sensors had melted and had damaged the cell next to it.
     
  18. LoveourPrius

    LoveourPrius Junior Member

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    Thanks for confirming. There were some different coloured lines marked on the cells that made me suspect that it had been rebuild. It worked extremely well for over 10 years and 400,000km so I'd like to keep on the road.

    I have 4 clips and 2 sensors. The middle temp sensor melted and damaged cell #14 (now reads 226+ V). I plan to replace all of the cells with a good complete set in the exact same sequence as I'm removing from a 2011. Can you suggest where I can get replacement wiring and sensors?

    I wonder if the Thermistor patch that Derekc spliced into place is still working. :)
     
  19. LoveourPrius

    LoveourPrius Junior Member

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    Hi Joe:

    Did you get a reply to your question, and have you tried splicing the Thermistor into you battery temperature sensor wiring? I have the same problem - my middle sensor melted so I need to splice in a new thermistor. Did the 3950 thermistor work? I'd appreciate any tips you can offer.
     
  20. Steven Walker

    Steven Walker New Member

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    Hi Gerry, while on here searching for info on those sensors to help you out, I found your post. Talk soon , Steve W
     
    #20 Steven Walker, May 26, 2020
    Last edited by a moderator: May 26, 2020
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