800v charging capability, when?

[Kaiju]

I disagree with this logic here. If you have a ~400v pack that charges at 500A (e.g. 200kw) with a capacity of say 50kwh, it would in theory take 15 minutes to charge it. If you scale that pack up to 200kwh, it takes an hour. If the charger is a 350 to 400kw charger that only offers 500A, both the small pack and large pack are hitting the amperage limit and stuck at 200kw. However, if the large pack is on an 800v setup and can still take 500A (e.g. 200kw), then it's going to pull the maximum charger power, significantly reducing the charging time.

Additionally, the 800v system helps with the large number of chargers with cables that are current limited (looking at you Chargepoint) that require 800v systems to fully utilize the charger.

The only "public" infrastructure that isn't 800v are Tesla chargers. Virtually all other DC chargers accommodate both voltage ranges.

The point wasn't that 800V doesn't have any applications in big packs. It was more that if you're dealing with a 150kW or 200kW charger, then going to 800V doesn't actually get you anywhere if you can already pull 500A. Also that a smaller vehicle may not be able to pull 500A at all and may see no benefit from a 400kW charger, but if it was limited to 250A it would see a boost at a more common, cheaper 150kW charger where a bigger one didn't.

As far as chargers and charger cables go, I suppose we agree there though maybe for different reasons. One of the points was that part of the whole conundrum is whether a station operator would bother to install things with huge capacity when not every vehicle could use it. So if you've got Chargepoint cheaping out on cables, are they going to put up stations capable of doing 350kW full bore on every stall?

One thing that was only touched on here is that you can't simply dump infinite power into a battery pack to make it charge faster, either. The charger voltage doesn't matter once you're dealing with pack cooling. Kilowatts are kilowatts and you're still charging the same number of 5V cells regardless of the charger voltage. If the limit is the charger, sure, 800V wins. But if you can't pull 400kW because your battery pack is getting too hot, well, you've gained nothing. Some of the numbers there are interesting.

A Rivian can charge at 220 kW max with a 140kWh pack. A Silverado EV can charge at 350kW with a 215kWh pack. If you just scale the energy coming into the battery vs size, you get 1.57 kW per kWh of pack for the Rivian and 1.63 for the Silverado. Not that much different despite 400V vs 800V. You'd also notice that the Silverado doesn't charge at 500A or the 550A that a Rivian would at max rate. Something else seems to be constraining how much power input it can accept. The interesting one seems to be Lucid with the gravity apparently having 400kW rates with a 123kWh pack, about double the power input of either Rivian or GM. Or at least, peak power. Tesla's best seems to be about the same as Lucid there with the Cybertruck, though the model Y only charges at 170kW.

Lucid doesn't use 400V or 800V. It uses 926V which...has no correlation to its superiority over its 400V or 800V competitors. That is clearly a result of pack design and cooling over anything else, and I don't believe there's any magic sauce there. Their battery pack has better cooling and the question there is if they're that much further ahead of everyone else engineering-wise or just made more allowances for cooling that came with compromises or costs their competitiors weren't willing to accept.

So when you look at a potential change to 800V(+?) and presumably 350kW charging, it's probably all coming down to whether or not the battery pack can handle that much power input, or if allowing it to do so makes it cost a lot more. So if you can't do 350kW input with the R2 battery pack, then there's no real point to going to 800V.

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[Gen(R3)Xer]

Guess I am not understanding the over engineered part.

I think that was more of my opinion of their justification for going from 800V to 400V. Just reading between the lines. It’s all about cutting costs and making more profit. They’re looking at the reality of public charging vs. home charging, which is statistically more prevalent right now. That’s where 800V doesn’t make a difference (at home). I completely understand that not everyone can charge at home. I was one of those folks and still kind of am despite my makeshift home charging setup.

This is from Kia:

"We're moving toward practical, affordable cars versus faster charging," Song said in Spain. "Our new cars have 400 V technology to save money on the overall cost. And besides, most owners charge from home anyway."

We want more affordable EVs on the road, right? Even RivIan is onboard with using 400V architecture to keep costs down. The R2 and R3 are going to be 400V, Tesla’s Supercharger network supports 400V. The Cybertruck is 800V, but it’s a flop. They’re not going to spend millions or even billions of dollars to upgrade their charging network just to support one vehicle that’s not a financial success.

 

[SeaGeo]

A Rivian can charge at 220 kW max with a 140kWh pack. A Silverado EV can charge at 350kW with a 215kWh pack. If you just scale the energy coming into the battery vs size, you get 1.57 kW per kWh of pack for the Rivian and 1.63 for the Silverado.

The Silverado is limited by 350kw charging stations and amperage with their big packs. Using a C rate comparison isn't particularly helpful there. If you look at the other 800v volt packs they tend to pull higher c rates. If you uncapped the R1 to an 800v system the leak rate would go up a decent amount, however the specific cells Rivian has used aren't particularly well suited to high power. Just imagine a scaled up Lucid Air charging curve.

Lucid doesn't use 400V or 800V. It uses 926V which...has no correlation to its superiority over its 400V or 800V competitors.

That's still an 800v class system.

It was more that if you're dealing with a 150kW or 200kW charger, then going to 800V doesn't actually get you anywhere if you can already pull 500A.

With this caveat, sure, I agree. However, there are a large number of 350 to 400kw systems in the ground and almost all of the new major build outs seem to be utilizing 400kw chargers.

One thing that was only touched on here is that you can't simply dump infinite power into a battery pack to make it charge faster, either. The charger voltage doesn't matter once you're dealing with pack cooling. Kilowatts are kilowatts and you're still charging the same number of 5V cells regardless of the charger voltage. If the limit is the charger, sure, 800V wins. But if you can't pull 400kW because your battery pack is getting too hot, well, you've gained nothing. Some of the numbers there are interesting.

Totally agree.

So when you look at a potential change to 800V(+?) and presumably 350kW charging, it's probably all coming down to whether or not the battery pack can handle that much power input, or if allowing it to do so makes it cost a lot more. So if you can't do 350kW input with the R2 battery pack, then there's no real point to going to 800V.

At the end of the day, Rivian is chasing cost and doesn't value fast charging times as much as other attributes. So they are putting their money elsewhere. It's as simple as that.

As long as the R2 does 10-80 in under 30 minutes I think it's fine for that class of vehicle.

I do think they need to push the Gen2 R1 to 800v and significantly shorter charging times to be competitive in the 100k market going forward.

 

[KRIV_ian]

As a slight aside SAE just published the updated J3400/2 which is the 1000V capability for NACS. SAE J3400/2 Update Brings Quicker NACS Charging | Sustainable Mobility Career Center

 

[KootenayEV]

800v charging capability will mean less heat while charging too, because of less current (amp) needs. So better thermals as a result.

Why do people keep saying this? At the pack level, all of the cells see the same voltage regardless of the system voltage (400 or 800v nominal). It will make zero impact to thermals.

 

[MountainBikeDude]

I'm not in any particular rush. I don't mind the 30 minutes it takes to charge 20-80% in the R1. I get to stretch my legs and ponder my place on this earth. I'm sure faster charging and better battery tech will be here soon enough. Until then, I'm cool with waiting a bit.

On my road trips, I haven't found it to be as dramatic as it's depicted by Kyle on out of spec. I also don't mind the time it takes to charge, and usually it's ready to go before we are. I do however agree with Kyle, that Rivian needs to step up their HVAC capacity. Running heavy DCFC sessions back to back in the summer heat, while also trying to run cabin cooling/pet comfort, can really start to derate the system and overall charging performance.

The main work around is to leave the vehicle, no cabin cooling running in the background, that way the system is solely focused on battery temp management. Really however, they do need to take thermal performance seriously, both cabin and pack running in extreme temps, not one or the other.

Part of me wishes they would adopt Mercedes G-Wagon pack design, with a triple stacked cold plate, top middle and bottom, rather than the singular middle plate. On the Rivian, i've noticed the least amount of regen fall off and best charging performance around the 40c temp range, unfortunately the system can't keep pace with the thermal build up under heavy DCFC in high summer heat.

I remember ages ago, my truck used to sound like a jet engine was kicking over in an attempt to keep the pack from that 55c upper limit, but seemingly they've massaged that a bit to give owners a better NVH experience while charging, likely at the cost of maintaining or getting ahead of the thermal load?

 

[Gen(R3)Xer]

As a slight aside SAE just published the updated J3400/2 which is the 1000V capability for NACS. SAE J3400/2 Update Brings Quicker NACS Charging | Sustainable Mobility Career Center

Will that go toward powering the Tesla Semi or are they just future-proofing the system?

 

[narmstrong79]

Cracks me up ya'll want native NACS and 800V. The majority of EVs released today are still in the 400V architecture , the large majority of superchargers are version 3 or less and can't support 800V.

You should hardly ever need public charging, so the few times you do 400V architecture is fine. Rivian need to better their thermal management for a better charging curve more than worry about 800v

 

[emoore]

Cracks me up ya'll want native NACS and 800V. The majority of EVs released today are still in the 400V architecture , the large majority of superchargers are version 3 or less and can't support 800V.

You should hardly ever need public charging, so the few times you do 400V architecture is fine. Rivian need to better their thermal management for a better charging curve more than worry about 800v

There are millions of people without home charging, pretty much all renters. So they need public charging. And while I don't mind waiting a few extra minutes on a road trip, it would be annoying to have to wait to charge at a public charge near home.

 

[DuoRivians]

Why do people keep saying this? At the pack level, all of the cells see the same voltage regardless of the system voltage (400 or 800v nominal). It will make zero impact to thermals.

For a given kW speed, 800v pack will see less current across all cells, assuming they’re in serial configuration. So less heat.

 

[narmstrong79]

There are millions of people without home charging, pretty much all renters. So they need public charging. And while I don't mind waiting a few extra minutes on a road trip, it would be annoying to have to wait to charge at a public charge near home.

Those people, probably shouldn't own EVs at all - Public charging as your primary source of "fuel" is dumb. It's as, if not more, expensive than gas ..especially if you value your time. Get a hybrid until you can get home charging.

 

[emoore]

Those people, probably shouldn't own EVs at all - Public charging as your primary source of "fuel" is dumb. It's as, if not more, expensive than gas ..especially if you value your time. Get a hybrid until you can get home charging.

I don't think that's a good idea. Need to get off oil ASAP and hybrid isn't going to help that. That's why most charging locations are in large cities. It's for people that don't have home charging.

 

[narmstrong79]

I don't think that's a good idea. Need to get off oil ASAP and hybrid isn't going to help that. That's why most charging locations are in large cities. It's for people that don't have home charging.

Everyone (who believes in climate change) says they want to get off oil, but many won't if it effects their wallet.

Hybrids can offer a transitional step for many drivers, reducing gasoline consumption even if not eliminating it entirely for those who don't daily commute or have very short commutes. Areas of larger population have a greater density of potential users, making the investment in public charging more commercially viable, since public charging is not a profitable business model. Lets not pretend that they do this for the betterment of the people, Its the best way to get federal and state funds for the project.

 

[pamalabama]

I think a point much less discussed in the 400 vs 800 volt discussion is the efficiency side.

Most people talk about faster charging which is a plus but you also have cost savings with smaller cable requirements. Additionally running at higher voltage makes the vehicle more efficient to run. The 800 volt architecture is one of the reason Lucid vehicles are so efficient in comparison to others.

Even though there would not currently be a lot of 800 volt charging stations today, the other things would pay dividends now moving to 800 volts.

Not a chance. Rivian vehicles are efficient because they optimize the vehicles for the EPA test to get the highest score possible. But the real range of rivian vehicles is bad by comparison.

New model Y EPA matches the model 3 with the same size battery. That is unlikely that the model Y is that efficient. EPA test is meaningless

Model 3 is more efficient than any lucid model. But EPA test does not reflect that

 

[SANZC02]

Not a chance. Rivian vehicles are efficient because they optimize the vehicles for the EPA test to get the highest score possible. But the real range of rivian vehicles is bad by comparison.

New model Y EPA matches the model 3 with the same size battery. That is unlikely that the model Y is that efficient. EPA test is meaningless

Model 3 is more efficient than any lucid model. But EPA test does not reflect that

If you are comparing Lucid to Tesla use the Model S, which is a similar vehicle in size and comparison.

That is like comparing the Fiat 500 getting 4.8 miles/kWh to the Model 3 4.3 miles/kWh.

By the way, although the Lucid Air is significantly larger than the Model 3, it is in the same effeciency ballpark with a 4.3 miles/kWh.

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