A primer on EV power contactors

[ctenidae]

It's easy to Monday morning quarterback, but I'm surprised a part this marginal was signed off for production.

Beancounters and marketing wanketeers winning over the lawyers and engineers, I suspect. I'd bet engineering is looking at the recall costs and the fix and saying "Told you so" and legal is looking at the potential for a class action suit saying the same thing.

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[sukhoi_584th]

Those specs are irrelevant based on how the contractors are physically connected to the HVBJB

 

[Tyldum]

Great post! I noticed you didn’t include WOT as a root cause. Given that Ford has included this as a contributing factor to these root causes, and it seems like a significant number of GTs have had this issue, do you think people should be concerned about trying to access the power in the car they paid for?

Only AWD LR here. I got the software for this over OTA (Norway). After driving actively for about 4 hours (narrow roads here, no highways, so WOT to pass quickly and safely), I got "service vehicle soon" and reduced power about 5-10 seconds after my last WOT. No DCFC yet that day.
Without the patch I would be careful, with the patch no worries.
Ford engineers agreed to clear the DTC and told me to be careful until the HVBJB is replaced.
They only focused on WOT, no worries what so ever about DCFC - which by the way seem to perform as normal even with the DTC present.

 

[Jimrpa]

good points....

I'd like to add that there ARE a whole differently designed class of contactors which are not dependant on a sealed case and inert gas... which is problematic with big fast temperature swings. Old School EVs commonly used open contactors for high current DC. These contactors rely on 'magnetic blowouts' designed to prevent arcing if the contact faces are required to snap open under load. When closing, there is typically a delay (precharge) before load is passed to prevent arcing and pitting.

considering that the HVBJB is a sealed area already, and does have pretty significant temp changes rapidly.... I am surprised the Design team went with sealed contactors.

I'm also surprised that the HVBJB space, fuses, and contactors cannot be reached, inspected, and replaced from the top down without dropping the battery tray. Having a removable lid for that section for access from the top down, perhaps ducted to/from the cabin even, would have enabled circulation of cabin temp air to help stabilize temps.

I was wondering why this component was so difficult to access as well and came up with a couple of (probably very wrong) theories:

• In modeling the failure rate, they probably determined that the component would have a very low failure rate and thus didn’t have to be very accessible
• Introducing panels and fasteners introduces manufacturing complexity and longer-term failures so they probably figured an access panel for a very low failure rate device wasn’t necessary
• Since the device is a high voltage device, they probably wanted to discourage “casual” access to high voltage components as much as possible (think about proposed designs for long term nuclear waste storage as something of an analogy)

 

[21st Century Pony]

Great, informative discussion.

 

[dtbaker61]

I was wondering why this component was so difficult to access as well and came up with a couple of (probably very wrong) theories:

• In modeling the failure rate, they probably determined that the component would have a very low failure rate and thus didn’t have to be very accessible
• Introducing panels and fasteners introduces manufacturing complexity and longer-term failures so they probably figured an access panel for a very low failure rate device wasn’t necessary
• Since the device is a high voltage device, they probably wanted to discourage “casual” access to high voltage components as much as possible (think about proposed designs for long term nuclear waste storage as something of an analogy)

but but but there are fuses in there..... its just wrong to put fuses in a place you can't check and replace..... oh wait, they did that in the Frunk too. ;(

 

[Jimrpa]

but but but there are fuses in there..... its just wrong to put fuses in a place you can't check and replace..... oh wait, they did that in the Frunk too. ;(

Same logic. Let’s be honest - when was the last time you replaced a fuse in a car? I think I may have replaced a fuse in the 1990s?

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