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Good News for Charging Convenience

Feathermerchant

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Charging miles added per hour is what is really useful when traveling. The less efficient the car, the longer you need to charge to travel the same distance. The chart below is a good example using Tesla home charging options for the 3,S and X.
Rivian R1T R1S Good News for Charging Convenience Tesla chage chart
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ajdelange

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People try to make this much more complicated than it is. Just as you probably have a good idea how many miles you get per gallon in your ICE cars you should have a pretty good idea how many miles you will get per kWh of electricity with your BEV. This you will learn from experience. For example in my driving (Tesla X100) i get, on average, 3 miles per kWh. It's a little more than that in the summer and a little less in the winter but if it rains it's appreciably less - more like 2.5. Thus if I'm charging at a 5 kW rate I'm picking up a bit more that 15 miles per hour of charging in the summer and a bit less in winter but only 12.5 if I will be driving in rain. This has to do with how I drive, where I drive and when I drive. The average X driver gets quite a bit less than I do so it is important to understand that what you get will depend on those same factors.

Now let's look at the table in the last post. It says that in a Model X charging from a 14- 50R I should get 20 mi/hr. The charger that comes with the X plugs into a 14-50R (if you have the 14-50 pigtail) and so is quite capable of a 40 Amp draw but it is limited to 32A and thus delivers 32*240 = 7.68 kW to the car about 90% of which, 6.9 kW, goes to the battery giving me, nominally, 20.7 mi/g = pretty close to what the table says. But if I charge from a HPWC plugged into a 14-50R it delivers 40 A and I'll get more like 26 mi/hr.

Use the table to get a rough idea of what charging rates will be and to help you plan your charging infrastructure but when on the road (or in your garage) use what you have learned and what the car tells you. In the Tesla there are trip odometers that tell you how far you have gone, how many kWh you have used and the average wH consumed per mile. When you undertake charging at home you set the charging level you want and thus can very simply estimate the miles added per hour of charging but you don't have to do even that because the car tells you how long it will be before charge completion to the charge level you have selected for the session. With an SC the situation is appreciably different because the super chargers taper the charging rate as the battery becomes fuller. Over time you will get some idea as to average SC charging rates. For example I find the average Tesla SC gives me 70 kW and the average CHAdeMO 40. Thus I expect to pick up 210 mi per hour of charging at a Tesla SC and 120 at a CHAdeMO station - on average. But I don't need to do any math at a Tesla station as the car knows the taper algorithm and tells me right at the initiation of charge how long it will take to get to the level I set.

But this is a Rivian forum. We don't know, of course, what Rivian is going to give us in terms of information displayed in the truck but I think we can be pretty confident that it is going to be similar to what the Teslas show and that therefore the same principles apply. For planning (of charger equipment needs and trips) we note that the big battery model will have a 180 kWh battery and a range of 400 mi. Even though we don't know what the usable capacity of that battery will be nor what actual EPA range will be let alone what we will experience in our own driving it's pretty clear that we are going to get something like 400/180 = 2.2 mi/kWh. Note that ABRP uses a number a bit below 2 in its Rivian calculations. Lets call it 2 to make calculation easy. A 14-50R outlet delivering the full 40A would send about 9.6 kW to the truck and the charging rate is thus estimated to be 19.2 mi/hr of charging. A charger that limits the draw from a 14-50R to 32 amps (as the Tesla charger furnished with their products do doubtless for liability reasons) will charge the vehicle at 4/5 that rate i.e. about 15 mi/hr.

The charger in the Rivian vehicles have a maximum capacity of 11.5 kW (charger fed by a 60 A circuit) and thus the fastest you can charge at home is about 23 mi/hr. At a 150 kW DC charger you would get, I'm guessing, perhaps 250 mi/hr based on data from ABRP which suggests that the EA high power stations deliver, on average, about 125 kW.

We have to accept that the Rivians are going to take about 450 Wh of energy to go a mile whereas the Teslas use as little as half to about 3/4 of that depending on model. And we have to recognize that the Rivian is going to have somewhat greater range than the currently available Tesla offerings (IOW I'm excluding the Cybertruck). These imply an appreciably bigger battery and, given the limitations of home charging capacity, longer charging times.
 
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skyote

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Excellent analysis & explanation @ajdelange , thank you!
 

Feathermerchant

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My point was just that the electrical charge rate and miles added to range are related but not equal between different cars. Operating efficiency is very important.
 

ajdelange

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I think people understand that they will go twice as far on a gallon of gas in a car that delivers 40 MPG as they will in one that delivers 20. I assume they can reason from this that they will go twice as far on a kWh of electric energy in a car that is rated at 4 mi/kWh as they will in one rated 2. I'm trying to get people to understand that it's the same thing except that the energy quantity is expressed via proxy in the ICE world (a gallon of petrol contains 33.41 kWh per gallon) and directly in the BEV world. Example: a car that gets 20 MPG is delivering 20/33.4 = 0.6 mi/kWh, only 20% of what a 3 mi/kWh BEV is capable. Hence the BEVs MPGe rating of 100 mi/gal.
 
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Lmirafuente

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Thought I would share the recent article for EA charging stations update. Electrify America completes 400 EV charging stations – about twice as fast as Tesla Supercharger rollout
https://flip.it/mfeGMA
 

Feathermerchant

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I don't see how there could be a valid comparison of EA and Tesla. One installs charging stations for profit. The other makes EVs and has a charging network exclusive to their cars and is NOT a profit center.
Tesla started building its exclusive network when it has a small fleet. EA is building an charging network using Dieslgate money for all other EVs in a time when there are a lot more EVs.
 

ajdelange

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Users don't care when the charging network was built nor why nor by whom nor at what rate. What they care about is their density (close enough together to alleviate range anxiety), location relative to the roads they use (e.g. a charger at a rest stop reachable without having to leave a freeway is preferable to one located at a shopping mall 5 miles from the freeway), reliability (is it working when you pull up), availability (are there enough stalls or do you have to wait on queue) and charging rate. Nor do they care about whether the operator is making a profit or not except as it reflects on the price charged per kWh.
 

Lmirafuente

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Users don't care when the charging network was built nor why nor by whom nor at what rate. What they care about is their density (close enough together to alleviate range anxiety), location relative to the roads they use (e.g. a charger at a rest stop reachable without having to leave a freeway is preferable to one located at a shopping mall 5 miles from the freeway), reliability (is it working when you pull up), availability (are there enough stalls or do you have to wait on queue) and charging rate. Nor do they care about whether the operator is making a profit or not except as it reflects on the price charged per kWh.
Agreed...the article was to do just that...help the range anxiety question. And who knows what Rivian will do in partnership with EA...time will tell (wink)...
 

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A bit of a side note, but I see repeated calculations assuming that Rivian will delivery no more than the minimum range numbers they have revealed.
As an example above, the calculation using 400 miles on 180 kWh is very likely too low.
1) Rivian has announced 400+ miles on the 180 kWh pack, and their track record shows that they tend to be conservative. More of the under-promise and over-deliver type of mindset. Even Chevy with the Bolt EV first stated 200+ miles of range and the EPA number came out at 238 - close to a 20% bump. When calculating efficiency, I would tend more toward number like 425 (which also may be low).
2) If the pack capacity is 180 kWh, it is unlikely that all of that will be useable. It depends on how aggressive they are in wanted to squeak every mile possible for the specs, but most manufacturers run about 90% of capacity actually available. That would put the Rivian at somewhere in the 160 to 165 kWh range on the 180 kWh pack (120ish on the 135). Tesla allow more pack % usage, but recommends against utilizing it on a regular basis and recommends charging only to 90%. I like this approach that gives you the extra range when needed, but most manufacturers choose to err on the side of caution and lock it out completely. It is also worth noting that there is no standard in what must be reported on battery capacity. BMW is very upfront and give both numbers (size and usable). The Chevy Bolt number (60 or 64 kWh) is the usable capacity. Others like VW give only the pack size and not usable. Tesla provides neither. Rivian seems to be reporting actual pack size, but that isn't really specified.

If you look at 425 miles on 160 kWh, it brings it up to about 2.7 mi/kWh. A significant difference than the 2.2 using 400/180.

Speculation? Absolutely. But probably a more reasonable estimate than taking the minimum range and maximum battery usage route.
 

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ajdelange

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A bit of a side note, but I see repeated calculations assuming that Rivian will delivery no more than the minimum range numbers they have revealed.
When Rivian says over 400 miles range this is not a minimum. It is their best guess as to what the vehicle's EPA rating will turn out to be. They've been driving their pre-production models around for quite a while now including all over South America so they now have quite a bit of kWh vs miles driven data and they should be closing in on a pretty good estimate of what the actual EPA rating will be. They haven't budged off the 400 mile figure but I note what seems to be less mention of "plus" than before. They will do everything within their power to reach 400 miles because coming in even at 396 just wouldn't look good even though it's only a percent shy of target,

2) If the pack capacity is 180 kWh, it is unlikely that all of that will be useable.
What is a 180 kWh battery? Batteries aren't like gas tanks which have a capacity beyond which you absolutely cannot fill them. And you don't get out all the energy you put in as some is lost to resistive heating in both directions. A battery is, by definition, full when its open cell voltage is at some level set by the engineers. Batteries can always be charged beyond "full" (to the battery's detriment). Similarly "empty" is defined by another, lower, cell open circuit voltage. Batteries can always be discharged below the "empty" level again to their detriment. So is a 180 kWh battery one that requires 180 kWh to charge it from empty to full or one that can supply 180 kWh in discharging from full to empty? IOW, they have a lot of flexibility in how they define the 180 kW rating. In fact a 180 kWh battery will be one that takes about 180 kWh to charge and can deliver about 180 kWh on discharge while the actual numbers might be 188 kWh charge capacity and 175 kWh discharge capacity.


It depends on how aggressive they are in wanted to squeak every mile possible for the specs, but most manufacturers run about 90% of capacity actually available.
Rivian will choose empty and full voltages in order to deliver an EPA rating of slightly higher than 400 miles without compromising battery longevity and, if possible, providing some usable energy at less than 0% SoC.


If you look at 425 miles on 160 kWh, it brings it up to about 2.7 mi/kWh. A significant difference than the 2.2 using 400/180.
Sure but the EPA range is probably not going to be as high as 425 though that's not impossible either. The biggest appeal of using the nominal stated battery capacity of 180 kWh and nominal stated EPA range estimate of 400 miles is that the ratio is close enough to 2 that you can use 2 mi/kWh for rough calculation and that's an especially nice number because it is 90% of 400/180 and statistics collected on the Tesla cars show that drivers overall realize about 90% of their car's EPA ratings (84% in winter and 96% in summer). Thus, all things considered, 2 mi/Wh seems a pretty robust estimate though ABRP would finds it a bit optimistic (they use 1.94 for the 180 kWh R1T but note that that is at 65 mpH cruise).

Now it goes without saying that some drivers will get better than 2 miles/kWh and some will get less. At the moment I'm averaging 116% of EPA while the worst drivers in the ensemble are only getting 40%. You will get what you will get dependent on your driving style and the kind of terrain an weather you drive in. On average assume 2 mi/kWh.
 
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DucRider

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Sure but the EPA range is probably not going to be as high as 425 though that's not impossible either.
Gentleman's bet on the EPA range? I'll take over 420 miles on the 180 kWh R1T and 320 miles on the 135 kWh version.
 

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Gentleman's bet on the EPA range? I'll take over 420 miles on the 180 kWh R1T and 320 miles on the 135 kWh version.
FWIW.....When I was at the Atlanta event this past fall I waited my turn to speak with RJ. While speaking with him he asked what model I planned on getting. When I told him the 135 kWh R1T he said that spec was getting ~ 325 miles on a full charge with the street tire spec.
 

ajdelange

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Gentleman's bet on the EPA range? I'll take over 420 miles on the 180 kWh R1T and 320 miles on the 135 kWh version.
Your guess is as good as mine at this point. The essential fact is that it's going to be around 400 perhaps biased a bit to the high side because of the aforementioned tendency of Rivian to under promise and over deliver. In any case it is going to be close enough that we can use 2 mi/kWh in our mental calculations without being more than a couple of percent off. These calculations are done on the road. We glance at the battery display and see that we have 47% SoC. Multiply by 4 and you have an estimated 188 rated miles left. Does it really matter that the rated miles may actually be 5% larger than this given that variable road and weather conditions put at least 5% variance into the equation? Similarly you are at a charger and see you have picked up 43% charge. That immediately translates to 172 rated miles added. If you only have 110 miles to go it doesn't really matter that the exact rated miles ore 180.6. It works the other way too. If you have 110 miles to go you know that you'll need nominally 22.5% battery to get there. If you have that plus a comfortable 10 or 20% more then you know you are fat. Having a nice round number like 400 is just awfully convenient. I guess I should mention that when I've posted this in other forums I've gotten angry responses that people don't want to have tp do higher math while they are driving. Any readers here that feel that way can rest assured that there will be plenty of displays that will relieve them of the necessity to do any math. And those fancy displays are entertaining in any case. I have to believe that Rivian will have them.

I suppose I should also mention that whatever the EPA rating turns out to be it will dwindle as the battery ages. EPA range of 420 miles at delivery may be down to 410 at the end of the first year and 405 at the end of the second. It's a fact of life and one that BEV owners tend to agonize over.
 

Havec

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I’ve been looking for data on how speed effects the mileage/range for Rivian vehicles. How much range does one lose by driving 80 mph verses 70 mph.?
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