Let's talk about charging on long distance travel?

kccougar

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Why wouldn't you just charge it at your destination where it is much much cheaper, isn't including the time in your driving, and better for the battery.
Because the charging options at my destination are not different than being on the road (this was only one leg of my typical round trip). But it is worth considering. I will run the numbers again for the full route, but I think the EV will only fall further behind in the comparison.

Edit - so I ran the numbers again, making it a round-trip route, which more accurately reflects how I use my vehicle. I cut out extraneous miles so a little more than 600 miles in one day, from southern Utah to Salt Lake City up and back about once a week.

ABRP app: Start 90% SoC. End 50% SoC. 11 hours duration. $69 in charging cost (I'm neglecting the 40% I would need to recharge at the end of my trip, both in time and money.

Current stats: Typically 8.5 hrs round trip. $34 in fuel, starting and ending with a full tank.
 
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CappyJax

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Because the charging options at my destination are not different than being on the road (this was only one leg of my typical round trip). But it is worth considering. I will run the numbers again for the full route, but I think the EV will only fall further behind in the comparison.
Why are you using the Standard Model S and not something closer in comparison with a range capable of the full distance?

There are free and cheap charging stations all over SLC. Just do some research. You are creating a worst case scenario.
 

DucRider

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I did that on purpose so that I would be comparing apples to apples. Leave with a full tank of gas, end with a full tank of gas.
It isn't really an apples to apples comparison, and those new to EVs often take a little while to catch on to the nuances.
No reason to either leave with a 90% charge nor return with one. Tesla recommends charging to 90% for daily needs, but charging to 100% just before a long trip is not only acceptable but is the very reason they have that top portion of the battery available to owners. With the ability to "fill the tank" at home, there is no need to top off before you get home (you'll wake up the next day with a full tank anyway). If you do not have the ability to charge at home (or at least at work), then an EV is very rarely a good choice anyway.

Since you are looking at a Rivian, the Model S in not an "apples to apples" comparison. The Rivian will charge faster (300 kW vs 125) and be available with longer range than the Tesla you are comparing to. A single 20-30 minute (or less) stop to charge should be ample to make the trip much of the year with a 180 kWh Rivian. In winter, an additional stop would likely be required (and might take a bit longer). There are many 350 kW stations on the major freeways in UT. Since you did not indicate a starting point.

As to cost, you need to look at your total driving and not just your once a week trip. The miles you put on the other six days will be much cheaper, and there will be no time spent fueling on those other days. Not sure what the factory service recommendations will be on the Rivians, but certainly no oil changes, tune ups, etc. Add in the cost of the 10K/yearly service, the AdBlue, belts, , , brake pads, ATF, etc (and factor in the time/hassle for the visits). A typical EV will have a tire rotation done every 7,500 miles and a cabin air filter every 15K. At 3 - 5 years some recommend coolant or other fluid changes. I don't know of anyone that has done brake pads on their EV, even at 175K miles.
 

kccougar

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Why are you using the Standard Model S and not something closer in comparison with a range capable of the full distance?

There are free and cheap charging stations all over SLC. Just do some research. You are creating a worst case scenario.
Not going for worst case, but I am going for conservatively realistic. I'm not running this exercise as a fan or a critic - I'm running it to see if I can get a good handle on what I can really expect if I go through with my Rivian purchase.

We don't have data on range yet for the Rivian. We talk about 400 miles, but should I go into an objective analysis assuming I can get 400 miles out of a single charge in a Utah summer (100+ deg) or a Utah winter (0 deg) running at a steady 84 mph with no regenerative braking? I think that would be foolish of me to assume. I went with a Standard Tesla Model S as a middle-of-the-road comparison.

Could I hunt out better charging station options? I figured the Tesla options would be sufficient for this comparison. For all but the SLC stop on my route there really aren't many other choices. Could I root out a cheaper option there? Maybe - but at the cost of probably another 20 minutes to the trip. Even then, it doesn't make up the 100% difference in cost.
 

DetachedGarage

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I completely agree! I sure hope they integrate Plugshare/Chargepoint/etc. into the navigation just like the Tesla UI. I do hope they open up the option for multiple destinations that Tesla does not have currently.

P.S. Love the location FL350 :) fellow AV Geek here.
1. I use Plugshare as well as the built-in navigator in my Tesla. I just did a quick route check on Plugshare and it showed about 8 CCS/SAE/Chademo (high speed) charging stations between Austin and Uvalde. There are also quite a few J1772 charging opportunities along the way too, albeit at a much slower charging rate. You might have to pay for some of these, but the point is- the charging infrastructure is there. There does seem to be a lack of any charging stations between San Antonio and Uvalde though. I like to use the Plugshare app as a good overview of my intended route because I can filter out only Tesla superchargers or include any type of combination I think I might need. I also use it for our road trips when booking a hotel. A lot of hotels offer free charging while you're a guest, so if the hotel is close to where I want to be or has the right amenities, then why not, right?

2. Personally, I'm surprised more gas stations don't have charging stations. I'm sure the old-school thinking of electric vehicles and coal-burning vehicles shouldn't mix is prevalent, but to me it seems like another stream of income for the station. It could also be a lack of real estate available too, but I seem to lean more towards the high cost in initial investment is limiting a lot of owners/operators from installing these.
 

ajdelange

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Not going for worst case, but I am going for conservatively realistic. I'm not running this exercise as a fan or a critic - I'm running it to see if I can get a good handle on what I can really expect if I go through with my Rivian purchase.

We don't have data on range yet for the Rivian....
Given this the best you can do is try to come up with reasonable estimates. The fact of the matter is that you won't know how a Rivian will perform on such a trip until you actually drive it. It makes sense to base the estimate on what you know and that is that an R1T will have a 180 kWh battery and a nominal (EPA) range of 400 miles for consumption of 180000/400 = 450 Wh/mi. Those of us with experience with BEVs realize that this is probably a reasonable number to start with based on the size and shape of the vehicle but we all know that whatever number you observe when you actually drive the truck it won't be 450. But let's start with that. You want to drive 600 miles. At 450 Wh/mi that will require 600*0.450 = 270 kWh energy. Assuming you handle the trip the way most people do you would leave home in the morning with 90% charge (162 kWh) on board and return home with perhaps 20% (36 kWh) so that you would be replacing 270 - (162 - 36) = 144 kWh on the road. The rate at which you will charge also depends on things we don't know but there are several of the big EA stations in Utah along the main roads (and given that you apparently average 85 mph or so on this trip I am assuming that you will be on the main roads). Given this I think it safe to assume that you will be able to charge at at least 144 kW which means that you will require an hour for charging. This, of course, depends on where and how you charge. Were I doing it I'd probably stop about half way, take on enough charge to get me to the destination with about 20% in the battery, charge at the destination with enough to get me back to the charger I used on the way up and then charge there with enough to get me home with 20% on board. Among other things this means starting at low SoC which will give me faster charging. Now an hour of charging at an EA station is going to cost you 0.99*60 + 3 = $62.40 = $0.43/kWh. That's really not too bad. And it might be a bit less than that as 144 kW may be a conservative estimate depending on the mood of the particular charger when you arrive and Rivians taper algorithm. You may also wish to include the cost of getting your truck back up to your nominal around town charge level. If you took it back up to 90% (most Tesla owners don't do that) you'd be adding 126 kWh at $16.38 (based on the 13¢ average cost of a kWh in the US) for a total energy cost of $78.78 equivalent to 13.13¢ per mile. Assuming petrol costs $2.50, any ICE vehicle that does better than 19 mpg will be less expensive to operate in this mode.

Now let's quickly rework the problem assuming that you can get the full 350 kW out of an EA charger (you can't). Your 144 kWh would be picked up in 25 minutes and your total bill from EA would be 3 + 0.99*25 = $27.55 for 19.2¢/kwh. That is a bargain! Your total energy cost for the trip would be $44.13 or 7.3¢/mi and an ICE car would have to deliver more than 33.9 mpg to best it in fuel cost.

So we have sort of bounded the problem. You are going to encounter charging time of more than 25 minutes but less than an hour on the road and give EA more than $27.65 but less than $62.40 for electricity. The fact that you plan to drive fast will push up the Wh/mi and cost but the fact that you may get better than 144 kW charging will push the charging time and cost down. Tail winds will help. Head winds will hurt. Cold weather will hurt. Use of the A/C in hot weather will hurt.

It's probably worth mentioning that 80% of BEV charging is done at home. With the average cost of a kWh and 450 Wh/mi consumption that's 5.85¢/mi.
 

Jehorton

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Can someone explain the 90% rule? If I do get a Rivian it will be my first BEV and I have not the first clue of charging and rates of charge. I see a lot on this forum but it’s a little over my head. I rarely drive far as it is. Maybe a total of 5 miles a day if I do drive. And I would charge from home almost all the time. Why is it bad to get a 100% charge? I’m guessing it has to do with battery degradation
 

ajdelange

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Yes, that's it. Bad things happen to a battery as it approaches full charge. The anode swells putting mechanical stress on the assembly, a lithium ion looking for a spot in the carbon lattice finding most of them already occupied may wind up reacting irreversibly with the SEI or worse yet with another lithium atom, more heat is produced etc. It's sort of like a propane tank. The more you fill it the less margin there is for expansion of the liquid if it gets hot. If you fill it full and the temperature rises it will burst so you never fill it full. "FULL" is 80% of it's capacity.

There is lots and lots more complexity with a battery than what I sketched and lots and lots of effort underway to improve the immunity of cells to these effects. Much of what you hear about the "million mile battery" has to do with process techniques, electrolyte additives etc. designed to increase battery longevity. If successful the manufacturer can effectively get more capacity because the protective buffer zones (there is one at the low end too) can be made smaller.

Note that it isn't "bad" to take on a 100% charge as long as one does not make a habit of it. If it were really bad to do 100% charging Tesla wouldn't allow it. Note that a battery can be charged above 100% but as that would be bad, the software prevents it. Also note that if you charge a Tesla over 90% frequently you will get a warning from the car that doing this will shorten battery life. And I believe that if you persist the BMS will step in and prevent it. The charging icon has a dashed line on it at 90%. I think it's labeled "trip" or something like. The intent is that for running around town you charge to less than 90% but if you want to go above that when setting out on a trip in order to have a little extra range insurance aboard that's OK as long as you don't do it too frequently.

Now Tesla could easily put the 100% mark at the point where the 90% mark presently resides and then say "Charge to 100% whenever you want". This, of course, lops 10% off the EPA range. So where the 100% mark goes is determined by marketing as well as engineering.

As an engineer I know that there are few cliffs in the natural world. Thus I suppose (and I could actually be wrong about this) that staying below 80% charge will buy me some additional battery health and that staying below 70% might buy me a little more. So I generally charge to 70% at home. But Elon has said that a daily charge to 90 is OK. 70% is plenty for my daily needs. When I take a trip I top up to 90% and wouldn't hesitate to go higher if my first intended charging stop were really far away.

Now all this will be at least somewhat different with Rivian. They have a different battery and a different BMS and where they have put the E and F marks on their battery gauge will be different too. They will give us some guidance as to how they want their battery managed
 
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DucRider

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Can someone explain the 90% rule? If I do get a Rivian it will be my first BEV and I have not the first clue of charging and rates of charge. I see a lot on this forum but it’s a little over my head. I rarely drive far as it is. Maybe a total of 5 miles a day if I do drive. And I would charge from home almost all the time. Why is it bad to get a 100% charge? I’m guessing it has to do with battery degradation
The 90% rule is unique to Tesla, and is often extrapolated by those with only Tesla experience to apply to all EVs. But that being said, even Tesla themselves recommends charging to 100% at the start of a long trip.
All manufacturers "lock out" a portion of the battery with a buffer zone at the top and bottom - what shows as 0% and 100% SOC on your "Fuel gauge" is less than the actual capacity of the battery:
1596556544872.png

BMW is one manufacturer that publishes both actual and usable capacities - as an example the 2020 i3 has a 33 kWh battery with 27 kWh usable. This means a 100% charge is 27 kWh. Tesla does not publish battery capacity at all (they used to have a number on their models that was loosely correlated to battery capacity, the they never claimed a P100D had a 100 kWh pack).

Tesla has a very small top buffer, and therefor recommends that owners not regularly charge to "100%". This allows Tesla to advertise their cars with greater range and let the owner decide if they want to take advantage of that opened up top buffer.

I think it unlikely that Rivian will take this approach and instead recommend that owners charge to 100% (they will have a built in top buffer). This a bit more conservative approach (fits with the Rivian mindset) and allows people to treat it like a normal vehicle - fill the tank when needed and drive.
It is unknown at this time if the 180 kWh battery spec will be the usable or actual capacity - there is no regulation as to what a manufacturer needs to disclose. Some of the best insight comes from the documentation submitted for the EPA range tests.
 

outdoors_jp

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This seems like a no brainer. Gas stations make money on all the other stuff you buy in the store. The gas attracts you in. Now they have the opportunity to keep you there for a little while longer while charging. Why wouldn't they want to install charging?
 

ajdelange

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Tesla does not publish battery capacity at all (they used to have a number on their models that was loosely correlated to battery capacity, the they never claimed a P100D had a 100 kWh pack).
That may be because it is not possible to express battery capacity other than approximately in terms of energy. Battery capacity is expressed in terms of charge, not power. When you charge a battery the coulombs have to flow through the battery's internal impedance resulting in heat production which is lost. When you discharge those same coulombs have to flow through the same impedance in the other direction and more energy is lost. Thus it takes more power to charge a battery from V1 to V2 than one can recover in discharging from V2 to V1. Looking at the the Tesla API's data I can estimate that the charging capacity of my Raven X battery is about 102 kWh and the discharge capacity about 88.5 kWh.

BMW is one manufacturer that publishes both actual and usable capacities - as an example the 2020 i3 has a 33 kWh battery with 27 kWh usable. This means a 100% charge is 27 kWh.
Are those charging or discharging capacities? Or is one the charge capacity and the other a discharge capacity?
 

ajdelange

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Why wouldn't they want to install charging?
They do. WaWa, Sheetz, QuickChek, Royal Farms.... It's just that a "gas station" is now more likely to be an establishment like one of those than the old Esso with nothing but pumps and a soda machine.
 

ajdelange

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i think it safe to assume that you will be able to charge at at least 144 kW which means
As it's a rainy day and it's always fun to fiddle with the numbers I looked at my Tesla charging history and found that Super Chargers charge my car at an overall average of 0.89C. If we apply that same number to the R1T it would give us an estimated average charge rate of 160 kW for the 180 kWh. At that rate 144 kWh could be loaded in 56 minutes.
 

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That may be because it is not possible to express battery capacity other than approximately in terms of energy. Battery capacity is expressed in terms of charge, not power. When you charge a battery the coulombs have to flow through the battery's internal impedance resulting in heat production which is lost. When you discharge those same coulombs have to flow through the same impedance in the other direction and more energy is lost. Thus it takes more power to charge a battery from V1 to V2 than one can recover in discharging from V2 to V1. Looking at the the Tesla API's data I can estimate that the charging capacity of my Raven X battery is about 102 kWh and the discharge capacity about 88.5 kWh.

Are those charging or discharging capacities? Or is one the charge capacity and the other a discharge capacity?
Capacity is a standard rating for amount of discharge energy available at a given temperature and C rate. There is no "charge capacity" rating that I am aware of (it does take more energy to charge than the battery capacity due to losses in the charging process - this becomes heat).
And capacity is indeed a variable that changes with temperature and discharge rate. Lower temps and higher discharge rates will result in less energy being available from a battery. Higher temps and lower discharge rates will result in more energy being available from the battery.

The BMW specs are the "discharge rating" of the pack (using your unique terminology) or the total energy available - 33 kWh is the total pack capacity. The vehicle BMS will only make 27 kWh of that available (from a 0% to 100% SOC). And yes, there will be less available at colder temps and/or higher discharge rates

According to the documents Tesla submitted to the EPA, it takes 114.8 kWh to fully charge your 2019 Model X using 240V AC power, so your 102 kWh figure makes sense (90% of charging energy is a darn good ballpark number for usable battery capacity)
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=48310&flag=1
 

ajdelange

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Capacity is a standard rating for amount of discharge energy available at a given temperature and C rate.
No. C is the capacity of the battery in coulombs or ampere hours. I gave the textbook definition (with the quote from the textbook) in a post way at the beginning of this thread.

There is no "charge capacity" rating that I am aware of..
That's because there is no "charge capacity" or "discharge capacity" if one interprets "capacity" correctly. They are the same (except for the, we hope, tiny fraction of ions lost to SEI and dendrite formation reactions.)

(it does take more energy to charge than the battery capacity due to losses in the charging process - this becomes heat).
And capacity is indeed a variable that changes with temperature and discharge rate.
Lower temps and higher discharge rates will result in less energy being available from a battery. Higher temps and lower discharge rates will result in more energy being available from the battery.
That's a fine list of the reasons we don't express capacity in terms of energy. The charge on a battery, usually expressed as some fraction of C, e.g. 0.7C, does not change with any of those variables while the energy we can extract from it, charged to 0.7C, does.

It is, of course, convenient to talk about capacity in terms of energy. If the vehicle uses 500 Wh per mile and can go 400 miles on a charge its battery capacity must be 200 kWh. That is, of course, the discharge capacity under average conditions just as the 400 miles is the range under average conditions.
 
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