Dashboard lit up after going over speedbump, module melted bussbar assembly

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by txexplorer, Apr 11, 2025.

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  1. txexplorer

    txexplorer Member

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    Wanted to post this to see if anyone knows what might've caused this (photo attached)

    I recently did a battery reconditioning with the prolong kit about a week before, this was my 3rd time doing it. Not sure if it's related, but worth mentioning. Car has been driving fine, good MPG, etc. but I went over a speed bump the other day rather fast and immediately the dashboard lit up. I thought at first it would go away, but after clearing the codes it came back.

    My OBD reader showed block 5 going wonky, so I knew I needed to take the battery out for inspection.

    Upon inspection, the bussbar assembly mount was melted to the modules. I had to pry it off.

    What could have caused this? Was the speed bump just a coincidence?

    Thanks in advance.

    IMG_0314.jpg
     
    #1 txexplorer, Apr 11, 2025
  2. Brian1954

    Brian1954 Senior Member

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    The nut on that stud was not tightened down to the proper torque, and the nut loosened up, which caused arcing between the stud and the bus bar. It looks to me like someone previously worked on the battery pack.
     
    #2 Brian1954, Apr 11, 2025
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  3. txexplorer

    txexplorer Member

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    Yeah, me :D

    That makes sense, I appreciate the input. I will use a torque wrench next time.
     
    #3 txexplorer, Apr 11, 2025
  4. Brian1954

    Brian1954 Senior Member

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    The torque for the nuts is 48 INCH-pounds (4 foot-pounds). You need to use a small 1/4" drive "bicycle "torque wrench.
     
    #4 Brian1954, Apr 11, 2025
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  5. PriusCamper

    PriusCamper Senior Member

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    A less likely cause for this is the cell behind that terminal is running hot and failed. Best way to eliminate hot cells during a rebuild is using a thermal camera. Cells that run hot usually test out as normal and then you're driving around wondering why the fan is on and the pack is running hot.
     
    #5 PriusCamper, Apr 11, 2025
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  6. txexplorer

    txexplorer Member

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    That was my next question, thank you very much Brian for your help.
     
    #6 txexplorer, Apr 11, 2025
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