HVBJB Failures - How Are People Driving the Vehicle?

[Jimrpa]

One thing I’m still a bit unclear on with the HVBJB failures is: How are people driving the vehicle? I see lots of references to “WOT” and “spirited” driving and such. My limited observations are that if I just press the accelerator to the floor and hold it there (which I’m assuming is the definition of “WOT”), the car will quickly accelerate to speeds above 100 MPH. Doing that on any roads where I live will pretty quickly get you pulled over and a serious speeding ticket. Does the HVBJB fail under mundane circumstances, for example driving around on 34-45 MPH roads?

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[RosarioM]

My failure happened going from about 25-35 on a 55 mph road. I had been driving for an hour and had traffic so never went over the speed limit. I fast charged it maybe once in the 8 months I had it. Bottom line, you can’t avoid the issue by just driving the speed limit. At some point, it will fail.

 

[DR.J56]

One can be WOT for 1/10 of a second or till the end of the battery charge. Your mileage may vary. If I’m feeling saucy I’ll accelerate WOT to the speed limit.

The contactors degrade over time, not suddenly. Even though the final event is sudden.

My undiagnosed failure happened while driving in a 30mph headwind at about 45 mph in 35 degree temps.

 

[bshaw]

I too am interested to hear responses on the topic.
If possible, provide ambient temps, duration of typical drives, and frequency of DCFC.

The only time I would consider WOT would be a short on-ramp to a highway where you need to get up to speed very quickly.

 

[Mach-Lee]

The BECM is mostly unable to detect the fault unless a high amperage load is present. This is why a WOT or passing maneuver is typically seen as the trigger. If you never floor the car, you may never get the "Service Vehicle Soon" warning message before getting "Stop Safely Now".

It all has to do with detecting that threshold voltage drop. Voltage drop is proportional to both resistance and amperage. The resistance will increase as the contactors degrade, but high amperage also needs to be present to register a high voltage drop which triggers SVS and the power limit.

As previously established in many forum discussions, there is not a huge correction with driving style and HVBJB failures. You can drive like a grandma and never DCFC and still get a failure. It's more luck of the draw with the part quality you got in your unit. Constant WOT usage and extended high speed driving definitely accelerates failure however.

 

[mkhuffman]

Todd stopped maintaining it in September, but I think the data he collected is very helpful to know the most common cause. Looking at the data, a sustained high rate of speed is the most common cause.

Often the error does not appear on the car's display until after the failure condition is detected, so that would explain why some people say they got the failure when driving at or below the speed limit. But the data shows exactly what was happening when the failure occurred.

Here is the data and the trend is obvious:
https://www.macheforum.com/site/threads/data-hvbjb-mega-data-aggregation-thread.21198/

Of course, that does not mean there are not outliers. But the data shows high speed, not WOT or DCFC, is the primary cause.

 

[JonathanEzor]

One thing I’m still a bit unclear on with the HVBJB failures is: How are people driving the vehicle? I see lots of references to “WOT” and “spirited” driving and such. My limited observations are that if I just press the accelerator to the floor and hold it there (which I’m assuming is the definition of “WOT”), the car will quickly accelerate to speeds above 100 MPH. Doing that on any roads where I live will pretty quickly get you pulled over and a serious speeding ticket. Does the HVBJB fail under mundane circumstances, for example driving around on 34-45 MPH roads?

FYI, "WOT" means "wide-open throttle," I think, so your assumption is correct. {Jonathan}

 

[Parasmoney]

What happened if the HVBJB fails after the car warranty expires?

 

[heisnuts]

Speaking as someone who has now had 3 failures (well, the third and updated part failure should be confirmed shortly by the dealer), it does not take a long time at WOT to toast the HVBJB. As most here know, I spend a lot of time out in the country on open roads with lots of curves, hairpin turns, switch backs, big elevation changes and 4 way stops in the middle of nowhere.

You are correct, it does not this car long to get up to speed at WOT. In my case, if it is from a dead stop I will be at WOT for about 4 or 5 seconds before I am letting up because I am at speed. It is even less time coming out of turns at WOT since I am already at 30 to 45 MPH at the apex of the turn when I go to WOT to accelerate out of the turn. Even though I am out in the middle of nowhere, I am on public roads so I have never hit 100 MPH. I do, however, have thousands of miles of these back roads where I will have these short bursts of WOT over and over and over again.

In my case this type of driving seems to toast the HVBJB in about 6,000 miles. I just dropped off the car today at the dealer so I will wait for their official diagnosis. However, the code in the system is the P0ADE, which was the same code last time I fried the HVBJB just over 5,000 miles ago and when they installed the new updated HVBJB at that time.

 

[heisnuts]

What happened if the HVBJB fails after the car warranty expires?

It has an 8 year/100,000 mile warranty. After that, expect to shell out around $3,000 to replace it.

 

[Jimrpa]

I appreciate a the responses and the pointer to Todd’s excellent data and analysis. I guess I’ll have to just wait and see if my turn ever comes up.
I should qualify my comment about my driving style: there is one very long on-.ramp to a divided, limited access highway that has Jersey barriers on both sides. Because of the way this ramp is accessed, there are some times (usually in the evening), when you can enter the ramp and come to a complete stop. I’ll do this, then floor the car until it hits 90 (100 if I’m feeling adventurous), then let my foot off the accelerator. By the time the car is approaching the open merge to the highway, it’s doing a sedate 60-65 (one-pedal mode). It’s a bit of a fun ride for friends who’ve never been in an electric car

 

[mkhuffman]

It has an 8 year/100,000 mile warranty. After that, expect to shell out around $3,000 to replace it.

That is BS, IMO. Ford better extend the warranty for this publicly known design issue. I am hopeful they will.

 

[phil]

I floor it whenever I feel like it, and have not had any problems yet.

Go figure.

 

[bshaw]

I floor it whenever I feel like it, and have not had any problems yet.

Go figure.

What trim level do you have, and when was yours built?

 

[Deleted member 16048]

That is BS, IMO. Ford better extend the warranty for this publicly known design issue. I am hopeful they will.

if they can find a solution within the warranty period, they won’t need to. Which is likely what they are doing. Trying to solve the problem itself and then replace them as they happen under warranty. Apple does this generally with quality issues.

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