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Burned down battery?!

Discussion in 'Gen 2 Prius Main Forum' started by Larry Kosher, May 2, 2022.

  1. Larry Kosher

    Larry Kosher New Member

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    Hello, petrolheads! (Shall I call you half-petrol-heads or something?)
    Here's the situation for you to crack on. 07 Prius, battery been rebuild by the unknown company at an unknown time. The car had been sitting for a few months (less than a year) before became used actively (maybe 5 k miles a month). Earlier this morning it wouldn't start and the red triangle of death popped up (no prior trouble codes). Upon connecting with techstream I discovered P3004. Investigating the issue further I found this in the battery (see the photos attached). A funny message on the ECU reads "Joe was here" (was it really Joe Biden messing with my battery?) Anyway, I checked all the cell voltages and they were fine (around 7.8 all of them). The car had a reasonable MPG prior to the failure (47). What could have caused this?
     

    Attached Files:

    #1 Larry Kosher, May 2, 2022
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  2. TMR-JWAP

    TMR-JWAP Senior Member

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    I would say Joe forgot to properly tighten the battery side terminal on that (+) main relay

    Looks like you're going to need a new (+) main cable, a new main relay, nut and the bypass wire.
     
    #2 TMR-JWAP, May 2, 2022
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  3. Larry Kosher

    Larry Kosher New Member

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    So, just a bad contact? I already replaced those and the car runs just fine.
    Thank you!
     
    #3 Larry Kosher, May 2, 2022
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    The only thing that would cause localized heat like that would be a high resistance connection at that joint or the immediate vicinity of that joint. Most likely from improperly torquing that fastener nut. 48 inch pounds by the book. Some DIYers use 60 inch pounds. inch inch inch pounds.
     
    #4 TMR-JWAP, May 2, 2022
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  5. Larry Kosher

    Larry Kosher New Member

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    I would assume that overtightening the bolts can create a better contact, not worse.
     
    #5 Larry Kosher, May 3, 2022
  6. bisco

    bisco cookie crumbler

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    yeah, don't assume. the battery can be deadly, and should not be taken lightly
     
    #6 bisco, May 3, 2022
  7. Another

    Another Senior Member

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    5,000 miles a month, wow!
     
    #7 Another, May 3, 2022
  8. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Until you strip the thread and wind up with 10% of the desired clamping force or less. It is remarkably easy to strip some of the fasteners in there.
     
    #8 Leadfoot J. McCoalroller, May 3, 2022
  9. mr_guy_mann

    mr_guy_mann Senior Member

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    An old saying is "tighten it 'til it breaks, then back it off half a turn".

    There are a number of posts from those who have broken off battery module studs.

    It really isn't that difficult to things correctly (according to the procedures and specs).

    Posted via the PriusChat mobile app.
     
    #9 mr_guy_mann, May 3, 2022
    Last edited: May 3, 2022
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