The battery fires at ECU sense connector thread

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.




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

 

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

 

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

 

Oo, hey, azurite too!

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

-Chap

 

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

-Chap

 

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

 

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