High voltage / Powertrain Malfunction (2024 premium)

[yusufq]

2022 GTPE, HVBJB went bad twice. Second time, it took >6 weeks to repair due to ?part shortage. I was pretty unhappy. Going through the Lemon Law process right now and just heard back that Ford will buy back the car. I think I am going to go through with it. Sad because I love the car otherwise, but I'm concerned what happens when the HVBJB goes bad after the warranty is out.

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[Maui]

So what happens when these go bad? Is this an install issue that damages it or a mfg issue where it wasn’t built right? Or perhaps just bad basic elements?

 

[Mach-Lee]

So what happens when these go bad? Is this an install issue that damages it or a mfg issue where it wasn’t built right? Or perhaps just bad basic elements?

It's a manufacturing and durability issue. Some of the contactors that aren't made perfectly tend to fail. It's a highly thermally stressed component if the vehicle is pushed hard.

 

[rcechinel]

2024 GT (Perf enabled)

Wtf?!?! This forum scares me.

 

[Dwood11]

You have a '24 model?

I have a 22 GT

 

[capsails]

It would be interesting to see the current load on the HVBJB. There was a previous post that looked at the part. It seems that it (the contactors) may be undersized for the current load. In our business, electrical components are to be sized for 200% of the anticipated load. I don't know what the loads on the Mach E are, but it would be interesting to see what they are, or if Ford has any measurements. The fuses on the HVBJB are 50A to 150A, which is also curious that the fuses are not blowing first before the contactors are frying. That maybe is indicative of a cumulative cycle issue, which also points to the parts (Contactors) being undersized for their purpose. Any Ford engineering input? I'm interested in hearing what is actually different between the Gen 1 HVBJB, and Gen 2? Also, have any changes to the contactors been made? What about thermal management, since the contactors are normally closed during normal operation or charging events? So, the issue occurs during start-up or initiating a charge event which is when the contactors close.

 

[Mach-Lee]

It would be interesting to see the current load on the HVBJB. There was a previous post that looked at the part. It seems that it (the contactors) may be undersized for the current load. In our business, electrical components are to be sized for 200% of the anticipated load. I don't know what the loads on the Mach E are, but it would be interesting to see what they are, or if Ford has any measurements. The fuses on the HVBJB are 50A to 150A, which is also curious that the fuses are not blowing first before the contactors are frying. That maybe is indicative of a cumulative cycle issue, which also points to the parts (Contactors) being undersized for their purpose. Any Ford engineering input? I'm interested in hearing what is actually different between the Gen 1 HVBJB, and Gen 2? Also, have any changes to the contactors been made? What about thermal management, since the contactors are normally closed during normal operation or charging events? So, the issue occurs during start-up or initiating a charge event which is when the contactors close.

GT pulls 1050 amps. Contractors are 500 amps but can take more for short periods. They melt under load and then stick afterwards.

 

[capsails]

GT pulls 1050 amps. Contractors are 500 amps but can take more for short periods. They melt under load and then stick afterwards.

Based on that, it would certainly be logical to consider the contactors to be undersized.

 

[pr0t0c0l_dr01d]

GT pulls 1050 amps. Contractors are 500 amps but can take more for short periods. They melt under load and then stick afterwards.

Is this a typo? GT pulls 1050 amps..is that at wot?

 

[Mach-Lee]

Is this a typo? GT pulls 1050 amps..is that at wot?

Yes, a kiloamp. Doesn't last long, but that's peak. Necessary to get the required power output with only 350V. Mine draws about 750 amps peak.

Fun fact, a GT generates twice as much heat in the contactors as an Extended AWD due to Joule's Law, which states that heat generation is proportional to amperage squared.

 

[capsails]

So, I looked and 2000-3000 amp DC contactors are readily available. it would be nice to know rationale to use a 500amp unit when load is well above this.

 

[heisnuts]

So, I looked and 2000-3000 amp DC contactors are readily available. it would be nice to know rationale to use a 500amp unit when load is well above this.

My guess is $$$

 

[Mach-Lee]

So, I looked and 2000-3000 amp DC contactors are readily available. it would be nice to know rationale to use a 500amp unit when load is well above this.

EV contactors are typically 300-500A, you don't often see ones bigger than that because it causes a lot of issues with packaging, cooling, and price goes up exponentially. Remember a 500A contactor can carry more than 500A for a short time. 500A is the continuous rating.

This is the current carry curve for a 500A rated contactor. You can see it can handle 1000 amps for 80 seconds, 4000 amps for one second, and 500 amps indefinitely.

The size of the wire or busbar attached to the contactor is important and affects this curve since the wire provides the heat sinking. In this case, the curve is for a 400 MCM conductor, which would be a solid copper wire about 5/8" in diameter. If the wire or busbar is smaller than that, then the carry current curve is less. The Mach-E uses a 3mm thick busbar, which is difficult to compare to a wire. But very roughly perhaps the equivalent of 175 MCM. This means our contactors should handle about 1000 amps for about 30 seconds cold. But after that the power has to be much more limited below 500A to prevent excessive overheating.

In summary, I think the 500A contactors are appropriately sized for the Mach-E, if anything the design flaw is the busbar the contactors bolt into is too thin for repeated runs at 1000A. GTs should used a different design of HVBJB with a thicker 5mm busbar to provide more heat sinking. The rest of the problem is just faulty parts that fail too soon even if engineered correctly.

 

[capsails]

It seems that due to failure frequency, it is undersized for load during normal operation. If the contactors are melting, it probably should have been a larger size. If we had engineered it, we probably would have chosen the 3000A Contactor. Although, our goal is bullet proof, not marginally acceptable.

 

[Dwood11]

So could it be an issue possibly with the high voltage wire connections not being crimped well enough causing excess heat due to resistance? I’ve dealt with this issue on high wattage inverters. Mainly on the battery side into the inverters.

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