ajdelange

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It just occurred to me that non engineering types might not be aware that power supplies are often rated in terms of their open circuit voltage and short circuit current ratings and that this may be the source of some confusion to them. The two ABB charger labels reveal that they both have 920 V open circuit voltage capability and short circuit current capability of, respectively, 350 and 400A.

The envelope boundaries for HPC150 - 350 classes show that any charger in one of these classes must have 920 V OC capability and 500A short circuit capability. Thus these ABB chargers don't belong to any of those classes (nor do they pretend to).

The AJC500 class requires 1100 V OC capacity and 600A short circuit current.
 
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At the risk of grossly over simplifying, this envelope specifies what the possible range of energy that could be supplied to the vehicle? This provides a "constant availability" that can be consumed by the vehicle.

The actual charge time and efficacy will be based significantly on the battery and environmental conditions at any given time along with the charger ability. As we see with Tesla, the data analyzed from the fleet will precipitate software changes that can increase efficiency and or performance.

The skill of the manufacturer and its engineers, is key to the ongoing efficacy of their power systems. I think often we overlook that with IOT type products we are as much buying into the manufacturer as the product. With established ICE vehicles you could very easily buy a Camry lets say, and likely never have to talk to Toyota again. Especially if its used. Obviously this has changed significantly in the last 20 years or so but it still applies. If I go buy a used camry today there are 30 independent shops in close distance that could service just about anything on my vehicle. With a tesla, or Rivian? well... Its more complicated.

I know some of this is basic no duh shit but I welcome anyone correcting me on these points. I am but a lowly Mechanical Engineer. But hey, at least I am not a civil engineer ;)
 

ajdelange

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At the risk of grossly over simplifying, this envelope specifies what the possible range of energy that could be supplied to the vehicle?
In engineering an "envelope" generally is used to specify limitations on combinations of parameters. In this case the power supply has a OC voltage rating of 1100V and can deliver up to 600 Amperes. But it can't deliver any combination. For example it can't deliver 600A and 1100V. If you take 600A from it it will immediately reduce its voltage to 833 V. Similarly in an aircraft weight an balance envelope there are limitations as to where you can locate loads. Put them in places that move the coordinates of mass and cg outside the envelope and you are not safe.

This provides a "constant availability" that can be consumed by the vehicle.
I can't figure out what you mean by that. Nothing is constant here. There are two degrees of freedom (voltage and current). In any particular design the two are tied together by the vehicle's load line but one cannot operate anywhere he wants along the load line. He must stay within the envelope. The the envelope represents the limitations of particular design as represented through the load line.

The actual charge time and efficacy will be based significantly on the battery and environmental conditions
Those factors and the design determine the load line.[/QUOTE]
at any given time along with the charger ability.
The only time the charger comes into it is if the load line extends outside the envelope which it cannot do. Then the charger limits the charge rate. The designer's job is to see to it that the load line does not need to penetrate the envelope to satisfy his needs. Rivian for example, wants to charge at 300 kW. As the chart shows, their load line does not reach the boundary of an HPC350 class charger. No problem. But it does penetrate the envelope of a HPC250 charger. Such a charger will not be able to charge a battery with this load line at 300 kW. Shouldn't that be obvious just from the class names? Yes and no. You don't need the diagram to see this for an 800 V system but you would need it to see that you can't charge a 500 V battery at a 300 kW rate at an HPC350 class charger.




As we see with Tesla, the data analyzed from the fleet will precipitate software changes that can increase efficiency and or performance.

The skill of the manufacturer and its engineers, is key to the ongoing efficacy of their power systems...
These are things that relate to the placement of the load lines. It is incumbent on the designer to place his load lines within the envelope(s) of the charger he intends his vehicle to use in such a way that the limitations of the charger do not degrade his required performance.
 
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I can't figure out what you mean by that. Nothing is constant here. There are two degrees of freedom (voltage and current). In any particular design the two are tied together by the vehicle's load line but one cannot operate anywhere he wants along the load line. He must stay within the envelope. The the envelope represents the limitations of particular design as represented through the load line.

Thank you for your reply, what I mean by constant supply is that the envelope is specific and defined. It doesnt change.
 
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This post no longer is fun for the non-engineers
I was worried a little bout that and why I tired to uplevel it a little. ;) I dont begrudge the conversation but you are correct deserves its own thread. However I want to specifically thank those that have taken the time to provide info. That is not a small lift.
 

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I was only kidding and merely pointing out I have not a clue what is being said haha
So let's see if we can pull out of this quagmire something that doesn't require technical expertise and is significant in terms of this thread's subject (the configurator) and may be significant to a prospective buyer. The thing that grabs me is the question, asked many posts back, as to whether the production Rvians will be able to charge at a 300 kW rate. Scaringe has promised that it will and he has proven to be a man of his word and therefore I expect that we will have 300 kW charging.

The question was asked because the truck is a 400 V truck. To be able to charge at 300 kW it has to be able to use a 920 V charger (the EA 350 kW units) and that implies that the production trucks will have to implement a battery pack modification which, it is presumed, is not installed in the pre production models. We only know of this modifiction because Rivian filed a patent application for it last year.

It is a significant question because if this mod is not installed we will be limited to 200 kW charging (even at an EA 350 kW charger) which is 2/3 of what we'd get with the patch and the implication of that is that charging time will increase by 50%. A half hour charge at 300 kW will take 45 minutes at 200 kW.
 
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It is a significant question because if this patch is not installed we will be limited to 200 kW charging (even at an EA 350 kW charger) which is 2/3 of what we'd get with the patch and the implication of that is that charging time will increase by 50%. A half hour charge at 300 kW will take 45 minutes at 200 kW.
I will now be watching for this...

Thank You
 

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RJ has stated explicitly that the vehicles will be able to charge at 300 kW.

He has also state that Rivians are designed out of the gate for 800V, but the components available for higher voltage architecture he estimated to be scarce until 2021 or 2022 (this was in 2018).

Details like design, placement and spacing connectors and busbars has taken into account the different requirements for double the voltage.

They have also designed the battery pack so that it can be easily switched from 450V (400V nominal) to 900V (800V nominal).
They will be using 2170 batteries from LG arranged in 15 kWh modules containing 864 cells. These can easily be configured easily as either 108s (450V peak) or 216s (900V peak). They will be split into two layers of 432 with an aluminum cooling plate between them. Those 15 kWh modules will be used to make the 105 kWh (7 modules), 135 kWh (9 modules), and 180 kWh (12 modules) packs.

RJ has definitively stated that they will be using 800V batteries at some point and that the battery pack and everything else in the vehicles is already designed and tested to accommodate that.
The main question is: Will they come out of the gate that way or will they produce for a year or two before making the switch?
Porsche, Lucid and GM (Hummer EV) all have been able to source 800V components for 2021 deliveries. Hyundai/Kia has stated the same. If component supply was the only thing keeping the Rivian from shipping as an 800V EV, has that been solved?
Or did the patent allowing 800V charging while using 400V components satisfy the biggest benefit to 800V (charging speed) and allow them to delay moving to a complete 800V system?

At LA Auto Show in 2018: “Power levels go up, charging speeds go up, everything gets better,” added Scaringe, in a much more enthusiastic tone. “As good as the vehicle is today, when we double the voltage it’ll be better.”
 

ajdelange

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The amazing thing about higher voltage is that other than less copper in the wiring to the battery and motors, there really isn't much advantage. For example a motor will draw half the current at double the voltage and thus require half the copper per turn. But twice as many turns are required to get the same flux! No gain for the motor. Well the I^2R losses go down by 4 per turn but you have twice as many turns so that means total I^2 losses are halved if you keep the same wire size. That would mean twice as much copper in the higher voltage motor and you know that's not what they had in mind. So they'll trade that off against I^2R loss. Maybe a small improvement.

The earlier discussions WRT the charger envelopes makes it quite clear how and why a higher voltage battery can be charged faster which of course means higher power levels so the first two parts of the quotation are obviously true. The third part ... well, yea, OK, maybe.
 
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Turns out the Hummer is using 400V components and batteries, but charging at 800V. Did they license from Rivian?
 

ajdelange

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Good question. I have seen Rivian’s patent application but not the patent. Was it granted? I'd say from the application that what they claim is so obvious as to be dodgeable under “prior art”. ???
 
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Good question. I have seen Rivian’s patent application but not the patent. Was it granted? I say from the application that what they claim is so obvious as to be dodgeable under “prior art”. ???
I haven't read the patent. Hopefully it is about more than just serial vs parallel circuits. Did they offer anything "novel" in terms of how the circuit might be dynamically reconfigured?
 

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Turns out the Hummer is using 400V components and batteries, but charging at 800V. Did they license from Rivian?
I have read a couple of other articles that dispute this and claim an 800V system is used. I am not 100% sure this guy is correct.
 

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