Rivian DCFC speed 300 kW?

DucRider

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It appears that Rivian has decided to implement their patent (https://pdfaiw.uspto.gov/.aiw?PageN....%2526OS=DN/20190126761%2526RS=DN/20190126761) to split 800+V (900? 920?) CCS and treat the HV pack as two separate packs. They will be in series when charging at a DCFC capable of providing 800+ volts, and in parallel during "normal" charging and during use.

R.J., in two separate statements says "up to 300 kW" and "max 300". Previous speculation has been 160 kW as the max.

Good news for those looking for the fastest charging as most Electrify America locations (at least near freeways) have 350 kW units.

This does bring up the question of pack voltage. I'm speculating a 108s (216s for high voltage charging) arrangement with 390V nominal (Audi, Jaguar) as opposed to the 96s 350V configuration (GM, Tesla, etc). As a note, the "800V" Taycan uses a 198s configuration with a nominal voltage of 723.
 

Billyk24

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One question: what does the charging curve look like? Tesla may advertise 250kW rate but...this rate is early in session and will quickly taper down some where around35%SOC.
 
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DucRider

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1591238367042.png


I'm guessing something like this.
Rivian A is taper starting at 50% (typical of most charging profiles)
Rivian B assumes an earlier taper at 25%
both assume 60% of max charge rate at 80% SOC (also typical)

My guide for this was data from Fastned (I approximated from the graph):
1591238935221.png

This graph also notes average rate when charging from 20 to 80% SOC which is a common fast charge strategy.


Model 3 charge graphs are readily available:
1591239047588.png


The M3 likely tapers so quickly due to the high amperage and C rates when trying to push 250 kW into an 80 kWh battery.

While Rivian has not released details, it is possible the 100 kWh versions (but not likely the 135) may charge at a lower rate than 300 kW. The SR M3 charges slower (200 kW) than the LR.

I believe the Rivian taper will look more like the typical charge curve as they can utilize high voltage vs high amperage when charging by making the pack act like an 800V pack (see the Taycan curve above). I would expect to see something similar from Rivian. It would be fantastic if it looked like the e-tron (non) curve and stayed at close to 300 kW all the way to 75+% ;).
 

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Model 3 V2 charging curve is unlike any I have ever seen. It also begs the question of whether an owner can set the peak kW charging rate at (150?) and the session might be faster due to a different charging curve?
 

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I wonder if RJ was referring to the 135 or 180 pack when mentioning the 35-40 minute charge time from 10-90%? The time would seem to align pretty close with the 135 kWh pack at an average charge of ~160 kW.
 

ajdelange

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Some Teslas, with their max battery size of nominally 100 kWh (380V or thereabout) can charge at up to 250 kW which is 2.5C. RJ says in the video that the Rivian will be able to charge up to 300 kW. It has a 180 kW battery presumably also at about 380 V. This implies a charging rate of 1.7C. That's more gentle than Tesla's charge rate. Given that why would Rivian go to an 800 V configuration for charging?
 
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DucRider

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Some Teslas, with their max battery size of nominally 100 kWh (380V or thereabout) can charge at up to 250 kW which is 2.5C. RJ says in the video that the Rivian will be able to charge up to 300 kW. It has a 180 kW battery presumably also at about 380 V. This implies a charging rate of 1.7C. That's more gentle than Tesla's charge rate. Given that why would Rivian go to an 800 V configuration for charging?
The only Tesla that can support 250 kW charging have 80 kWh packs (LR M3). The S and X with 100 kWh packs support 200 kW charging (along with the SR M3 and its 55 kWh battery).
Tesla uses a 96s configuration resulting in a nominal pack voltage of 350V. Audi and Jaguar have gone to 108s configurations giving a higher nominal battery voltage of ~390. A 96s configuration can charge at 400V
I think it likely that Rivian will use a 108s configuration, with the capability to switch to a 216s configuration while charging if the charge equipment supports it. This results in a 450 or 900 charge voltage which happen to be the numbers used in their patent listed above.

As to why...
Utilizing "800V" allows their customers to charge twice as fast on the installed CCS charging network.
I can't think of a better reason to implement it than cutting charge time in half.

Electrify America uses efafac and ABB units, which have specs of 350A @ 920 V (efafac) and 375A @ 920V (ABB). If Rivian charges at 400V, the max charge rate would be 140 kW on the efafac or 150 kW on the ABB. If the charge voltage is 450, the charge rates would be 160 or 170 (some rounding done).
Charging at 800 (or 900?) volts doubles those speeds and lines up with the 300 kW number RJ is using. Rivian tends to under-promise, so a DCFC rate of 315 kW (or more) could easily be touted as 300 kW.

As a note, the CCS standard allows up to 400A and 1000V, so the 160 kW charging quoted by Rivian at one point could have been 400A @ 400V. But in any case, by adhering to the CCS standard the maximum amperage is 400 and the only way to increase charging speed is to increase voltage. Or ditch the standard and build your own network from the ground up. I very much doubt Rivian will choose the latter.

As to why charging is tending towards higher voltage - smaller, more manageable cables is a primary factor. Porsche claims a weight savings of 66 lbs in the Taycan by moving to their 800V architecture inside the vehicle. That's a lot of copper. There is no physical reason the oven (water heater, clothes dryer, etc) in your house couldn't run off of 120V, but the wiring to support it would need to be much thicker and more expensive, both for materials and installation costs. Switches and relays would also need to be beefier.
 
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thrill

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Voltage selection is of course going to be driven by multiple factors. Pre-engineering, there's the forecast of why spend (additional) resources on something that might have minimal availability in charging stations, have known lesser availability in the parts supply chain, and would need to be recouped cost wise in an already price conscious market. In engineering, there's the plus side of wire current capacity vs cross sectional area, easier bendability during routing before damage to the wire or the shielding, a more complex to design, test, manufacture, and support electrical switching system if allowing for multiple voltage options (we're going to be unhappy if said switching turns out to be a weak spot needing frequent replacement in the merely occasional use of high voltage charging units). However, marketing wise it may be judged valuable to be one of the few high voltage capable systems on the market, especially if you consider design and delivery of cutting edge technology a significant plus in the capturing of multi-billion dollar contracts from the likes of Amazon, etc. and potential contracts such as being the sub to some larger organization wanting to fulfill USPS vehicles in the future, etc. As for physics limitations on charging, that's going to be driven mostly by heat dispersion, especially with present day battery chemical makeup, where hot spots are too easily formed during charging causing ever growing damage (though there's self-healing anodes, etc. in the lab, who knows yet about viability at production levels). Then of course, frequent heat issues, if you don't really have an engineered design allowing life-long high rate charging, can affect warranty service, driven by your internal desire vs expense to be viewed as the manufacturer of choice, or your willingness to capitalize on your customer goodwill and quietly change warranty specifics as some have done.
 
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DucRider

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Not affiliated, but did sent them a "news tip".
 
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