The battery fires at ECU sense connector thread

Discussion in 'Generation 1 Prius Discussion' started by ChapmanF, Mar 19, 2015.

  1. ChapmanF

    ChapmanF Senior Member

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    My goodness that's interesting. How strange that pins 21 and 22 are so severely plagued with the green stuff, while all 20 other pins look pristine. Also strange that, in your shot from the back of the shell, pin 22 looks as bad there too, but 21 does not.

    Also there looks to be some kind of grainy deposit on the inner surface of the connector shell, near pins 14 to 19 or so ... any ideas on that?

    Was there any sign of a possible source of the (what looks like) brown gunk around that edge of the connector shell, or what it might be? Was the sense wire harness changed out too (I hope)? What was going on at its connector?

    The way the ECU mounts in the battery box, is the gunked end of the connector up, or down?

    Has anybody posted a pinout for that Gen 2 connector, or have you worked it out by looking? (That's what I did for the Gen 1 connector, obviously a similar design but different pin count, and who knows how they might have shuffled the wire order around between generations.)

    I'm curious because in most of my experience with car electrics, the places most prone to the green stuff (which I guess is malachite, with maybe some brochantite if there's sulfur around) is on a copper pin that spends a lot of time more electropositive than the stuff around it. It attracts whatever (negative) carbonate ions might be around.

    [​IMG]


    But I think in Gen 1, the highest pin numbers correspond to the negative end of the battery (and the Gen 1 pinout alternates pin columns so if pin 24 is most negative, 23 is third most negative, with the second most negative being pin 11. But none of that matters if Gen 2 swapped things around.

    Anyway, I guess the ion-attracting behavior depends on a pin being more positive than something ... in a typical 12V car there's usually no question what the something is, it's the negative-grounded body. But the traction battery case is supposed to float, isolated from any battery voltage. In this case maybe pins 21 and 22 are more positive than some voltage that leaked to the case.

    Yeah, it would be interesting to know the pinout. Or the source of the brown gunk.

    -Chap
     
    #21 ChapmanF, Apr 23, 2016
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  2. Texas Hybrid Batteries

    Texas Hybrid Batteries Active Member

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    upload_2016-4-23_19-23-5.png upload_2016-4-23_19-24-6.png


    upload_2016-4-23_19-25-33.png

    Pins 22 and 21 are the primary negative and Bat Block 2 Voltage connection. I have 7 ECU's in my shop right now that have the same corrosion on the same 2 pins. We replace the computer and the harness anytime this stuff shows up to prevent the shorting issue that we've seen before.
     
    #22 Texas Hybrid Batteries, Apr 23, 2016
    Last edited: Apr 23, 2016
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  3. ChapmanF

    ChapmanF Senior Member

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    Thanks!

    The arrangement looks a lot like Gen 1, adjusted for the smaller number of modules.

    Now ... who's the chemist who can suggest why two of the three most negative pins of B12 would be growing malachite, but not pin 11 which electrically is the middle of the three?

    I'm finding this a bit of a brain teaser ....

    Unless ... some manufacturing defect where the female contacts in the cable connector have often been loose at 21 and 22 ... if the contact isn't good, could it be those two pins grow malachite because they are more positive than the contacts they are shoved into?

    Or ... some circuit defect in the ECU such that it constantly draws (sources, if you prefer) a small current on those two pins ... again making the pins more positive than the contacts they are in (I guess that also presupposes the first problem, a high contact resistance)?

    What do the female contacts look like, when the pins look like this?

    -Chap
     
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  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    A very plausible theory regarding a slight connector defect which becomes apparent after an extended service period.
     
  5. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    The HV ground fault detection circuit runs through pin 22. A good description of this circuit can be found here.
    Prius battery exploration Thanks Hobbit !

    My WAG is that the most negative (pin 22) and the ground fault connection promote the growth of malachite. I think pin 21 picks it up from proximity. Pin 11 has just a bit more distance from pin 22.

    The ECU I pictured has been sitting on a shelf for quite awhile. The brown stuff on the connector edge is magic marker. I sent Texas Hybrid Batteries a bunch of replacement ECU's today. He said he didn't need anymore corroded ones.

    A little Googling on malachite shows it is soluble in weak acids.

    Brad
     
  6. ChapmanF

    ChapmanF Senior Member

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    Magic marker. Aha! Now we know the telltale sign to look for! :)

    Interesting about the ground fault circuit. I'm not sure the proximity WAG satisfies me completely, just because there's such a striking difference between pins 21 and 22, which grow stuff, and all 20 other pins that look completely mint. Pin 11 doesn't even grow a little bit of stuff.

    In other cars where I've seen the most malachite is usually on connectors that are (a) in the elements, say in the engine compartment, (b) not well sealed (saw it mostly in older cars before the rubber packed terminal shells in newer ones), and (c) on a pin that had constant +12V applied. It was distinctive enough I could find a connector like that where one pin would be green, and say to myself "I bet that's a circuit with constant unswitched +12 and a switched ground, and the green pin is the +12 one" and look it up and be right. What made it grow so much malachite was it was always growing, hour after hour, day after day.

    So I wonder whether the ground fault test can be the whole story, if it is only applied when the car is on. I'm wondering whether there could be some more long-term effect, like, maybe the ECU has two sample/hold circuits connected to alternate pins, and the selection switches always fall back to 21 and 22 when the car's off, and some constant small leakage current results? This is complete speculation as I don't know nearly enough about how the ECU is designed, but I wonder if it could be something like that.

    -Chap
     
  7. Texas Hybrid Batteries

    Texas Hybrid Batteries Active Member

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    Here is what I have guys, you can speculate as to what it means. It looks like 22 and 21 are normally affected but on some 11 is also starting to corrode. 6 and 7 are also affected on one unit. The top one hadn't shorted out yet but I suspect it was very close.


    upload_2016-4-24_18-15-54.png upload_2016-4-24_18-16-43.png upload_2016-4-24_18-17-26.png upload_2016-4-24_18-17-55.png
    I ended up ripping the wire out of that one but it was number 22.
     
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  8. ChapmanF

    ChapmanF Senior Member

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    Oo, hey, azurite too!

    I had no idea that crud was so beautiful under a microscope. :)

    -Chap
     
  9. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    Here is one more to add to the list. Just pin 22 has the malachite. The back side is clean.

    WP_20160426_15_00_22_Pro.jpg
     
  10. DRACO

    DRACO Member

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    Wow, going to take a look at MIL's.
     
  11. hobbit

    hobbit Senior Member

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    Some folks reading this may have no idea who I am; I haven't been
    active here in *years*. However, Chap specifically alerted me to
    this thread a while back and I finally chased it, and then went to
    check my own car. I've still got the same 2004 of yore, still with
    all the weird hacks in it 240K on the clock, and the original battery
    still in place and truckin' along just fine from what I can tell.
    No mystery sense-harness crystals here, but I've got a few ideas
    about what's going on that may make sense and help lead to a proper
    diagnosis.

    12 year battery revisit

    The pack also got a connector-strap refurb, since I had a set of the
    plated ones on hand, so that's detailed too. This is all life-cycle
    stuff that Toyota probably never *could* have possibly tested to the
    timeframes we're in now, only tried to predict. So it's another part
    of the continued industry learning process.

    Feels weird to be posting here again. My excuse for dropping off
    was that I wanted to wait till I got some really epic roadtrips
    between 2010 and 2013 all written up before posting again, e.g.
    to offer useful/interesting content, and that never happened as
    I wanted while other projects and plain ol' laxity intervened.
    Such is life; with all the pictures and detailed notes I collected
    at the time it may still happen. It's been quite the decade of
    adventure with this car in general.

    _H*
     
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  12. bisco

    bisco cookie crumbler

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    THE hobbit? has j.r.r. tolkien come back to life?:p
     
  13. ChapmanF

    ChapmanF Senior Member

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    As I suspected, the main effect of pinging hobbit into the conversation would be to make my own posts look hasty and shallow.... :)

    -Chap
     
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  14. hobbit

    hobbit Senior Member

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    Not at all, it is quite the mystery. I maybe helped localize it
    a little, but didn't sit there trying to scope everything and
    analyze all the current flows. Corrosion or no, I appreciated
    the heads-up and the implicit too-long-fallow opportunities that
    fanned out from that -- tearing the car apart again, taking geeky
    stuff to local shows to help educate the masses, and even posting
    on PC again.

    It would be interesting to look at the equivalents in 3rd and
    4th gen cars, to see if any of the technology has changed. In
    the thinking-model of eventually moving to lithium, I'd almost
    expect to see a little circuit across each module connected to
    a common data bus, that not only reports module status but maybe
    even helps with some active balancing.

    _H*
     
  15. FireFighterHill

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    I'm pretty sure I have this same type of corrosion on my traction battery. Is it safe to drive this way? Would cleaning it with a weak acid or mechanically fix the issue? Im a big believer in using dielectric grease on connections to keep this kind of thing from happening.
     
  16. ChapmanF

    ChapmanF Senior Member

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    Well, really, none of us knows what's safe. The inspiration for this thread was a series of six reported Prius fires that began in that area.

    Can you post pics?

    It would clearly be safe to replace the sense harness with a new one (part number is a link in post #2) and the ECU with a clean one. The harness is only $125ish, probably not worth the time to try to disassemble and clean. The ECU is pricier, you might want to see how clean you can get the pins ... it comes down to you and your comfort level.

    My own leaning would be toward great conservatism as to adding any kind of substance around those pins that Toyota didn't choose to put there. This is not a typical 12V connector, there's up to about 320V between the farthest two pins at some times. You certainly don't want anything that leaves any conductive residue, or that would be sticky and collect dust etc.

    -Chap
     
  17. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    Close to 100% of the Gen I batteries have at least some corrosion on the voltage sensing wires at the the battery terminals.

    Somewhere around 1% of batteries have the corrosion on the ECU pins

    Have you pulled the orange plug and looked at the ECU pins?

    Brad
     
  18. ikefor

    ikefor Member

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    I have seen quite a number of ECU with pins 21 and 22 burnt up, roughly about 60% of failed Pri packs that i have come across have this issue that infact in some instances, i just figure that i look at the pins first when i have access to the pack. Living in Africa, i reakon that heat also exacerbates the buildiup of malachites

    A case in point is this friend's Dorman battery with a burnt up ECU and voltage of 78V measured from negative terminal to ground.

    Besides heat, i would really want to have more information as to what may be the cause for this issue.
     

    Attached Files:

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  19. ChapmanF

    ChapmanF Senior Member

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    This is not a Gen 1 example (and a good thing too, because the forum no longer lets me edit post #1 to add to the list), but there's been a sense-harness-connector incident in a 2007.

    -Chap
     
  20. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    Well here is one more guys. It's a Gen II junkyard pack so I do not have background info on the car.

    WP_20160904_14_51_55_Pro.jpg

    WP_20160904_14_51_31_Pro.jpg

    Here is the interesting new info. Modules one to four came out of the pack nearly drained. It makes sense that those four modules supplied the energy to pins 21 and 22 to start the fire. Their voltages had held around 7.4 volts which was less than the rest of the pack. On initial discharge they had only 200 mAh left in them with the rest having 2000 to 3000 mAhr. They recovered to 5200 mAh modules. The rest of the pack is stuck in 3XXX range.

    I have no idea why.

    Brad
     
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