HVJB Deep Dive: Is there any way that software fixes the problem of overheating contactors?

[Shayne]

Professor John D. Kelly at WSU
See the contactors of a 2021 Ford Mustang Mach E GT high voltage battery. See the removal procedure and a functional demonstration of the contactors.
This is a great video from WeberAuto -

Found this interesting in the comments. link

"SMTSHREK

Great video professor! A lot of quality in depth information, even for a ford master tech like me who has hands on experience with Mach-e’s for the last couple months.gotta say you break it down way more and better than fords web base training and the hv battery repair class, thank you! I’ve replaced a handful of HVBJBs already mostly all in GTs or standard and with extended range battery, and I’ve been dying to open one up to see how they tick like you just did but ford has been calling them back almost as fast as I take them out. Thank you for showing the insides.

A few things I’d like to share…..
The recall is a module programming that will modify contactor performance and ford is hoping will save the hvbjb from having to be replaced. But software will not 100% fix hardware and some contractors are still failing, so much ford released a tsb this week to replaced hvbjb.

That leads to my next tid bit of Info, you mentioned electrify America maxes out at 350A which is under the dc fast charge rating of the Mach e, but the dc contactors can’t handle that even though it’s working it’s rating. All the failures I’m seeing are welded positive dc charge contactors after charging at an electrify America station…..

Finally i hope I didn’t miss you mentioning it, but it should be mentioned that both contactors may fail closed and set dtcs for both contactors.battery will not be denergized and is not safe to open. No choice but to replace the $26,000 battery. Now with current failures of the dc charge contactors both may stick without setting the dtcs needed by ford to replace the battery. I’ve worked with engineering to get at least one unstuck and so far it’s worked. So hopefully ford is working on a fix for that.

Keep up the good work, looking forward to more videos!

WeberAuto

Thanks for the kind words and the great information. Stuck shut contactors is no more dangerous than working inside the battery. Just unplug the battery positive and negative cables from modules to the junction block and the power will be removed from the junction block. I understand why Ford would take thin stance, but unless I am misunderstanding something, it is not a big deal. Personally, I cannot see how stuck shut contactors would damage anything else inside the battery."

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[voxel]

HVAC comes off the black box neg contact similar to the dc to dc and ac charger. Need to flip it up top or the alternator down. (in blue). Still wonder if the pre-charge + contact closes before the main + for these 50 amp circuits. Is it for the inverter capacitors as was explained or is always used?

I think this was discussed at the very end of the video. The DC-DC and HVAC systems bypass the main contactors which is great because the MME can charge the 12V without the main contactors.

To turn on the main contactors you need to go through the rigmarole of negative contactor, pre-charge, positive contactor - which seems excessive for HVAC and DC-DC charging.

 

[voxel]

Found this interesting in the comments. link

That leads to my next tid bit of Info, you mentioned electrify America maxes out at 350A which is under the dc fast charge rating of the Mach e, but the dc contactors can’t handle that even though it’s working it’s rating. All the failures I’m seeing are welded positive dc charge contactors after charging at an electrify America station…..

This is an interesting comment..

 

[Marcel]

Current is dependent on mostly the motor configuration, not the battery configuration.

RWD, least amount of current
AWD, more current
GT, most current because front motor is more HP

Current during DCFC is 150 vs 115 kW is a significant factor and ok RWD Standard battery least likely but still the recall massage.

 

[Ming]

Current during DCFC is 150 vs 115 kW is a significant factor and ok RWD Standard battery least likely but still the recall massage.

believe they wanted to play safe, and the OTA fix is very cheap. if they are forced to replace the hardware, likely would only do on models with higher current draws.

 

[AZBill]

Current during DCFC is 150 vs 115 kW is a significant factor and ok RWD Standard battery least likely but still the recall massage.

DC charging is not likely the real culprit here. The rear motor is 210kw, AWD front motor is 50kw, the GT front motor is even higher. 150kw charging is below the steady state rating of the contactors and 150 kw is only for a few minutes. This is why WOT is more likely the cause of the degradation, not DCFC.

 

[AZBill]

This is an interesting comment..

This is false. The Signet Chargers at EA are rated to 500A, and there is no conclusive evidence these failures are all happening due to fast charging.

 

[RobbertPatrison]

HVAC comes off the black box neg contact similar to the dc to dc and ac charger. Need to flip it up top or the alternator down. (in blue). Still wonder if the pre-charge + contact closes before the main + for these 50 amp circuits. Is it for the inverter capacitors as was explained or is always used?

The way you drew the schematic- with the HVAC on the same contactor as the Chargers - would be better. That allows the battery to be cooled or heated without swithing on the motor inverters.

Unfortunately, that is not the way the HVJB appears to be wired, at least from what I see in prof. Kelly's the video. Perhaps that is because that would require a larger - more expensive - contactor. This maps the actual part to the schematic:

The Cabin HVAC fuse is spot-welded on the left of Main Contactor- (Right bottom).
The charger Contactor is the black box in the middle and it connects straight to the 0V battery. The bus bar for that is a little hard to see but it is tucked under the top part of the HVJB plastic.

I do suspect that anytime the positive main contactor+ (left) closes, the pre-charge contactor closes before that to avoid the spark.

 

[voxel]

This is false. The Signet Chargers at EA are rated to 500A, and there is no conclusive evidence these failures are all happening due to fast charging.

Right... because we have folks here with HVBJB failures without ever DC fast charging.

The question is... is it more common when DC fast charging?

 

[Shayne]

I think this was discussed at the very end of the video. The DC-DC and HVAC systems bypass the main contactors which is great because the MME can charge the 12V without the main contactors.

To turn on the main contactors you need to go through the rigmarole of negative contactor, pre-charge, positive contactor - which seems excessive for HVAC and DC-DC charging.

Can get away without the negative main and possibly the pre-charge contacts. Not needed and not used are 2 different things.

WeberAuto

Thank you, yes the black contactor bypasses the main negative contactor and precharge is not needed.

Now wondering if this is the circuit that closes when you are in accessory mode. Power no brake mode. I would think it is the accessory contact and the circuit you add to in such cases a police cars?

The way you drew the schematic- with the HVAC on the same contactor as the Chargers - would be better. That allows the battery to be cooled or heated without swithing on the motor inverters.

Unfortunately, that is not the way the HVJB appears to be wired, at least from what I see in prof. Kelly's the video. This maps the actual part to the schematic:

The Cabin HVAC fuse is spot-welded on the left of Main Contactor- (Right bottom).
The charger Contactor is the black box in the middle and it connects straight to the 0V battery. The bus bar for that is a little hard to see but it is tucked under the top part of the HVJB plastic.

I do suspect that anytime the positive main contactor+ (left) closes, the pre-charge contactor closes before that to avoid the spark.

You mean the positive. He explains quite clearly that all those accessories run through the black box accessory contact (50 amp fused). You show it throw the main negative which is not correct from what I understood.

 

[voxel]

I don't think there is a stronger argument than this HVBJB to move to 800V or 1000V architecture for the GT/GTPE.

 

[RobbertPatrison]

I don't think there is a stronger argument than this HVBJB to move to 800V or 1000V architecture for the GT/GTPE.

800V cuts the current in half, which is good for loss and heat. But it requires different inverter electronic components, wiring harness isolation. Thank makes it more expensive., so I don't think Ford will do that in the short term.

 

[SnBGC]

The way you drew the schematic- with the HVAC on the same contactor as the Chargers - would be better. That allows the battery to be cooled or heated without switching on the motor inverters.

Why would the inverters need to be switched on? They don't appear to be passing power through to the ACCM or PTC. If the vehicle needs to heat or cool the battery while charging then it could simply close that large negative contactor and then the ACCM and PTC would have power available. The motor inverters would remain powered down (if I understand how the system works...)

One question I have is: IF that scenario occurs......(the car wanting to power on the ACCM or PTC while charging)....then does it first shut off the small black negative contactor BEFORE it closes the large negative contactors of can they both be closed at the same time? Is there some sort of diode to prohibit power back feeding through one of those circuits? Is back feeding power even a thing in a DC circuit anyway?

 

[Ming]

DC charging is not likely the real culprit here. The rear motor is 210kw, AWD front motor is 50kw, the GT front motor is even higher. 150kw charging is below the steady state rating of the contactors and 150 kw is only for a few minutes. This is why WOT is more likely the cause of the degradation, not DCFC.

even DCFC peak current is lower than WOT, it typically runs long time (tens of minutes) comparing to seconds of WOT. the contactors and box is in an enclosed environment, heat could accumulate over time.

 

[Shayne]

even DCFC peak current is lower than WOT, it typically runs long time (tens of minutes) comparing to seconds of WOT. the contactors and box is in an enclosed environment, heat could accumulate over time.

There are 4 contacts involved for DCFC 2 for driving which are different set ups. Who knows if that has something to do with it and all 4 generate more heat even at lower amps? Just what one person is seeing, interesting and worth the debate. Can't believe all you read on the net.

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