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Project Lithium Pack Upgrade: Voltage Sense Wire to orange BMU connector sizzling and warm to touch

Discussion in 'Gen 2 Prius Technical Discussion' started by The Beast1, Apr 20, 2024.

  1. The Beast1

    The Beast1 Junior Member

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    Hello everyone,

    I am doing the project Lithium replacement pack. My NiMh cells went bad right as they had new packs so I opted for a lithium replacement.

    I've made more than halfway through and am now reconnecting everything. My wire harness that handles the volt sense to the BMU had corrosion on it but not that bad. I cleaned it with electrical corrosion cleaner and scrubbed it down. To finish, I rinsed it off with contact cleaner.

    I pushed the wire harness onto the lithium pack blades and began buttoning everything up. When I started booting down the wire harness bolts to the lithium packs, I heard a distinct sizzling noise. I panicked and disconnected everything thinking I some how shorted it.

    I did this a few more times before I realized I was indeed doing it correctly. I decided to move forward.

    Eventually I realized where the sizzling noise was coming from. The orange BMU connector was noticeably hot to the touch.

    This didn't seem right at all so I disconnected it all again. This time I pulled out the bmu and examined the inside. There was no obvious corrosion or burnt components.

    My question is, is the connector supposed to get hot? I believe the answer is no. If so, is this indicative of a bad wire harness?

    Pics are a before and after of the harness itself. I removed a lot of corrosion .

    Thank you for any guidance.
     

    Attached Files:

    #1 The Beast1, Apr 20, 2024
  2. AzusaPrius

    AzusaPrius Senior Member

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    Just get a new set of bus bars from AcenBay.com and use promo code "azusa"

    After that if there is still sizzling then know it is your cars components that are defective and not the lithium modules.
     
    #2 AzusaPrius, Apr 20, 2024
  3. The Beast1

    The Beast1 Junior Member

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    Unfortunately, the bus bars aren't used with the lithium packs. Just the volt sense harness. Here's what I am talking about.
     
    #3 The Beast1, Apr 20, 2024
  4. ChapmanF

    ChapmanF Senior Member

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    I suspect that something in your cleaning methodology left a path of slightly conductive residue between some of the pins.

    Gotta be careful with that harness. It looks innocuous enough, but the voltages between some of its pins are fairly high.
     
    #4 ChapmanF, Apr 20, 2024
  5. AzusaPrius

    AzusaPrius Senior Member

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    @The Beast1

    I do not understand what you mean by the bus bars are not used with lithium.

    You need bus bars to connect everything properly, I understand that one side is not used but it still needs bus bars.

    Yours are very corroded and should be replaced with a new lithium battery.
     
    #5 AzusaPrius, Apr 20, 2024
  6. The Beast1

    The Beast1 Junior Member

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    You are indeed correct. Upon the third time I connected it the issue went away.
     
    #6 The Beast1, Apr 20, 2024
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