When or will GT/PE 5 Second limit be lifted by OTA

[Mach1E]

Explain how that's undersized. Placing a nickel next to it tells me the size, but not that it's undersized.

Im not an EE, but the Mach-E’s busbars look similar to other 400v systems. Looks like the Model Y might even use aluminum.

Exactly.

It may seem absurd, but apparently they work. Anyone even “broken” a bus bar yet?

Every time I see a plane take off and fly it seem absurd too.

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[Mach-Lee]

Explain how that's undersized. Placing a nickel next to it tells me the size, but not that it's undersized.

Im not an EE, but the Mach-E’s busbars look similar to other 400v systems. Looks like the Model Y might even use aluminum.

The exact measurements on the Mach-E are 20 x 3 mm. Based on sizing references (here's just one), that's good for about 325 amps continuous give or take. Good engineering practice says you shouldn't really exceed more than about 2x the continuous rating for decent thermal performance. Based on that, the bus bar for the GTs should have been thickened to around 20 x 5 mm to support about 500A continuous/1000A peak. The GTs should have had a beefier HVBJB than the non-GT models, but the busbar is the same size in GT and non-GT HVBJBs.

It's hard to tell, but the busbar in the model Y is thicker than the Mach-E. Probably 4 or 5 mm thick.

The Model Y Performance might have an even beefier junction box compared to the standard version, but I can't find anything on that.

 

[Mach1E]

The exact measurements on the Mach-E are 20 x 3 mm. Based on sizing references (here's just one), that's good for about 325 amps continuous give or take. Good engineering practice says you shouldn't really exceed more than about 2x the continuous rating for decent thermal performance. Based on that, the bus bar for the GTs should have been thickened to around 20 x 5 mm to support about 500A continuous/1000A peak. The GTs should have had a beefier HVBJB than the non-GT models, but the busbar is the same size in GT and non-GT HVBJBs.

It's hard to tell, but the busbar in the model Y is thicker than the Mach-E. Probably 4 or 5 mm thick.

The Model Y Performance might have an even beefier junction box compared to the standard version, but I can't find anything on that.

All sounds good, but still seems a bit theoretical.

We know we already push 1000 amps through these busbars.

So has anyone broken one?

If not, no way we can concluded they’re “undersized” if they get the job done without failures.

 

[AKgrampy]

Exactly.

It may seem absurd, but apparently they work. Anyone even “broken” a bus bar yet?

Every time I see a plane take off and fly it seem absurd too.

No - because there is a power limit to protect it. Now I am not saying it can not be pushed a bit but that buss is fairly small for 1000 amps. I am interested to see what the OTA brings us even though I may never avail myself of it.

BTW - we can get 1000 amps thru the HVBJB too - until we can’t

 

[Mach-Lee]

Here's some more pics of a model 3 penthouse from this eBay listing:

The busbars at the top might be aluminum but they are thicker than 3 mm. The ones touching the contactors (black things) are copper covered with some kind of silver foil. But under that you can see they are THICK right next to the contactor, probably 7 mm thick if I had to guess. The use of copper and great thickness next to the contractors is for heat sinking (to help dissipate heat from the contactors). Again, this is much thicker and beefier than our 3mm bus plate. The greater thermal mass bolted to the Tesla contactors helps them perform for longer than the Mach-E.

 

[BigMach-E]

Here's some more pics of a model 3 penthouse from this eBay listing:

The busbars at the top might be aluminum but they are thicker than 3 mm. The ones touching the contactors (black things) are copper covered with some kind of silver foil. But under that you can see they are THICK right next to the contactor, probably 7 mm thick if I had to guess. The use of copper and great thickness next to the contractors is for heat sinking (to help dissipate heat from the contactors). Again, this is much thicker and beefier than our 3mm bus plate. The greater thermal mass bolted to the Tesla contactors helps them perform for longer than the Mach-E.

Okay, I’m not an EE either. However, I do know something about the costs of metals. A pound of nickel on the commodity market is $8.45 roughly. So, hypothetically, what we are basically saying is that at two pounds of nickel to have bigger bus bars, cost of less than 17 bucks, Ford decided to cheap out on a 60-70 thousand dollar car, guaranteeing it wouldn’t live up to the promises it’s marketing department was making of a “track ready” vehicle.

That’s what’s absurd.

 

[AKgrampy]

Okay, I’m not an EE either. However, I do know something about the costs of metals. A pound of nickel on the commodity market is $8.45 roughly. So, hypothetically, what we are basically saying is that at two pounds of nickel to have bigger bus bars, cost of less than 17 bucks, Ford decided to cheap out on a 60-70 thousand dollar car, guaranteeing it wouldn’t live up to the promises it’s marketing department was making of a “track ready” vehicle.

That’s what’s absurd.

I could be in “la la land” on this but I thought I read it somewhere that Ford was caught flat footed by the battery supplier. It was the supplier who placed the restrictions which Ford was unaware of until too late. I may be totally in left field on this but still bad on Ford.

 

[Mach-Lee]

Okay, I’m not an EE either. However, I do know something about the costs of metals. A pound of nickel on the commodity market is $8.45 roughly. So, hypothetically, what we are basically saying is that at two pounds of nickel to have bigger bus bars, cost of less than 17 bucks, Ford decided to cheap out on a 60-70 thousand dollar car, guaranteeing it wouldn’t live up to the promises it’s marketing department was making of a “track ready” vehicle.

That’s what’s absurd.

It's tin or silver coated copper, so it gets better if we assume it would have been two extra pounds of copper instead of nickel, so like $10 more in metal. Total cost is a little more complicated than that but yes, for $10 more in materials they might have been able to eliminate the 5 second rule.

Either somebody didn't catch this in time, or their objection was overruled due to potential increased cost or schedule delays.

 

[BigMach-E]

It's tin or silver coated copper, so it gets better if we assume it would have been two extra pounds of copper instead of nickel, so like $10 more in metal. Total cost is a little more complicated than that but yes, for $10 more in materials they might have been able to eliminate the 5 second rule.

Either somebody didn't catch this in time, or their objection was overruled due to potential increased cost or schedule delays.

And, on top of that, it might have decreased the likelihood of HVJB failures in the field. Again, I’m no EE, but doesn’t greater thermal capacity in the system generally mean less stress on all of the components involved?

Cutting corners avails nothing. It’s estimated to cost Ford around 2k for each warranty failure of a HVJB. That would be about 200 cars with better bus bars.

 

[Mach-Lee]

And, on top of that, it might have decreased the likelihood of HVJB failures in the field. Again, I’m no EE, but doesn’t greater thermal capacity in the system generally mean less stress on all of the components involved?

Cutting corners avails nothing. It’s estimated to cost Ford around 2k for each warranty failure of a HVJB. That would be about 200 cars with better bus bars.

Yes, thicker metal and the resulting greater heat capacity would have been easier on the contactors. But due to manufacturing defects, I still think the old contractors would have failed living an easy life. The HVBJB burn rate would have been slower, but still present.

 

[Hammered]

Okay, I’m not an EE either. However, I do know something about the costs of metals. A pound of nickel on the commodity market is $8.45 roughly. So, hypothetically, what we are basically saying is that at two pounds of nickel to have bigger bus bars, cost of less than 17 bucks, Ford decided to cheap out on a 60-70 thousand dollar car, guaranteeing it wouldn’t live up to the promises it’s marketing department was making of a “track ready” vehicle.

That’s what’s absurd.

Ford does that often in the wrong areas. They need someone with a brain saying "no bean counters, you're not gimping that part". Calculating loads isn't rocket science. This is pretty common place. The calculations were what they were, and then they built dozens of test articles. Batteries can be tested on load simulators. There's nothing here that caught them by surprise except for the HVBJB.

You can have chatGPT with advanced data analytics build these charts with ease. Here's a 20x3mm busbar at 18" long at 1000a taking thermal resistance into account. Starting temp is 70F.

I don't think the limiting factor is the busbars, it appears to be the rear drive motor's feed. That appears to be at best around 2 gauge, and the numbers for it are bad. It's ~80" long in the battery and has another 18" or so before it goes into the inverter.
2ga wire, 90" long, 70f initial temp, 600 amps

Given the insulation used on these, I think the numbers look more like this

 

[Mach-Lee]

Ford does that often in the wrong areas. They need someone with a brain saying "no bean counters, you're not gimping that part". Calculating loads isn't rocket science. This is pretty common place. The calculations were what they were, and then they built dozens of test articles. Batteries can be tested on load simulators. There's nothing here that caught them by surprise except for the HVBJB.

You can have chatGPT with advanced data analytics build these charts with ease. Here's a 20x3mm busbar at 18" long at 1000a taking thermal resistance into account. Starting temp is 70F.

I don't think the limiting factor is the busbars, it appears to be the rear drive motor's feed. That appears to be at best around 2 gauge, and the numbers for it are bad. It's ~80" long in the battery and has another 18" or so before it goes into the inverter.
2ga wire, 90" long, 70f initial temp, 600 amps

Given the insulation used on these, I think the numbers look more like this

That's interesting, but there are a lot of variables that go into those calculations like ambient temp, insulation, wire orientation, spacing, convection, etc. Probably a ballpark but I don't really have confidence in ChatGPT to do proper engineering calculations yet.

I think the rear motor wires are bigger than 2 AWG, from photos it looks like the rear motor wires in the pack are 0.5" diameter externally which would translate to a 1/0 AWG EV wire. Probably 150ºC insulation.

https://www.champcable.com/product/exrad-xle-1000-volt-cable/

^ In that case, the ampacity of 1/0 is listed as 339A in free air 40ºC.

See if you can run 1/0 in confined space 40ºC ambient 675A?

 

[BigMach-E]

Give us 8 seconds full power, and I think we would stop complaining. At least I would. I know we are likely never going to get a sub 12 sec quarter mile, but the throttling happens at like 75 mph from a dead stop, and it’s even worse if you are moving and perform a WOT.

 

[AKgrampy]

I am not saying it happened but I can certainly believe someone dropped the ball and at the last moment realized “it’s rated for 1000 amps but only for 5 seconds” and then it was too late to make any physical/design changes. NASA crashed a dang mars lander because someone used imperial versus metric (or vice versa) and miscalculated the landing. Engineers are not perfect (I resemble that statement) and sure bean counters try to save costs but shaving $10 - $50 in buss bar versus $2000 (plus rental and gas) per failure is a no brainer.

 

[Hammered]

That's interesting, but there are a lot of variables that go into those calculations like ambient temp, insulation, wire orientation, spacing, convection, etc. Probably a ballpark but I don't really have confidence in ChatGPT to do proper engineering calculations yet.

I think the rear motor wires are bigger than 2 AWG, from photos it looks like the rear motor wires in the pack are 0.5" diameter externally which would translate to a 1/0 AWG EV wire. Probably 150ºC insulation.

https://www.champcable.com/product/exrad-xle-1000-volt-cable/

^ In that case, the ampacity of 1/0 is listed as 339A in free air 40ºC.

See if you can run 1/0 in confined space 40ºC ambient 675A?

ChatGPT simply feeds the formula into code interpreter (now called data analytics). At first it wasn't taking into account thermal resistance values, the values are post thermal resistance instruction turning them into curves, not lines. By using it to check its work, it pans out. Don't use the base LLM to do calculations, have it write script then check its work. There's much more utility to be had with API access than just using the browser w/ plugins.

I'd have to get in the battery with my dial calipers to truly put the entire picture together. Given contactors are a failure point, it's safe to assume they're a weak link. The cabling cannot be overlooked. I've got cables from the hybrid F150, they've got 3 layers of insulation with a foil shield between them. 30% or more of the diameter you see is insulation, if even that little. My 2ga welding cable is larger than the battery's internal rear run based on weber auto's HVBJB removal vid (below)

Here's your request...

And at its 339a rated capacity. Notice the curve shapes.

Just had it combine them.

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