Why do hybrid battery control module connectors get corroded?

The voltage potential from pin to pin is ... 19v maybe, unless the arcing is across rows, but that would blow pins off at the base, not cause corrosion wouldn't it?
Being DC, the electron flow is one direction, are there tell-tale signs that one end of a busbar corrodes more than the other?

T1 Terry

 

I tend to agree... I think it was Jack at saltyhybrid.com who first described it as "micro-arcing" between pins. But maybe that is not as accurate as simply saying the corrosion on that first pin creates signal noise that screws up the ECU's ability to produce accurate charge rate data.

 

This isn't high current flow across any two connector pins (at least not initially). It's the high voltage potential that makes the materials "more reactive" - and more likely to form corrosion. I might think that vibration is also a factor by causing fretting or wear at the terminal to pin interface.

IDK what the voltage threshold is to make this all happen, but all I can do is guess based on the observations. The orange HV connector is the one that "always" has problems. I do not see or read about corrosion at the low voltage connectors.

I would think that they chose to use gold plated terminals to help reduce corrosion problems, but they still happen.

I haven't seen enough ecu failures to know if any particular group of terminals "gets hit" more often than others. I just deal with it when the car is in my bay.

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A constantly-applied potential of even 12 volts is enough to really speed up the growth of malachite on connector terminals ... that's what used to be seen under the hoods of old cars before we had good weathertight sealed connectors. A pin on a constant unswitched +12 circuit would pretty much always be more covered in green stuff than its only-intermittently-powered neighbors.

I strongly suspect (but haven't tried to find out for sure) that the speed of the reaction depends on the voltage gradient. So if you have a terminal at +12 that's an inch away from something grounded, there's a 12-volt-per-inch gradient there. If it's half an inch from something grounded, that's a 24-volt-per-inch gradient, and so on.

The orange connector has a bunch of terminals all pretty close together and not far from a grounded case, and the pin-to-pin voltages are anywhere from 14-ish up to a couple hundred depending on which two pins you pick.

I've long thought that generating a plot of the voltage gradients (taking all of the pins into account) superimposed on the geometry of the face of that connector would be a fun graphing exercise, only so far I haven't had the time for that much fun.