On my first long trip in my new MY LR. Range is only 2/3 in 48F but the main issue is discrepancy in charge prices between what shows on navigation and what I got charged. Anyone have any clue about this?
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Discrepancy in charge prices
- Thread starter chowdarygm
- Start date
The next charger I stopped is even more outrageous at first 4 minutes itself at $0.68/m+ tax. I am not understanding what is happening.
RayK
Active Member
@chowdarygm The cost for Supercharging at that station is based upon the power level being delivered at any moment in time. The highest cost, $1.15/min, happens when you first plug in as your battery's state-of-charge is the lowest. At that time you may be pulling 200kW of power so you get charged (monetarily) at the $1.15/min rate. As you continue to charge, the power level will gradually decrease and then you'll fall into the other rates; <180kW, <100kW, and finally at the very end of the charging session, <60kW.
What's listed as your charging fees in both the Tesla's navigation display and from within the Tesla app, show identical costs / min. If you multiply the times at each given rate (e.g., 5 mins x $0.22 = $1.10) you should see everything works out. The session times all appear to be rounded to the nearest minute so that might be where the error is in total power delivered to the vehicle. Some of it can also be due to the inherent charging losses as not all of the energy being delivered by the Supercharger gets into the HV battery.
The app probably should show each cost-of-charging-time in chronological order, not by cost rate. In other words, the $1.15/rate should be displayed first in the list as that is what's happening during the charging session; the highest cost/min is at the start of charging and the lowest cost/min is at the end.
What's listed as your charging fees in both the Tesla's navigation display and from within the Tesla app, show identical costs / min. If you multiply the times at each given rate (e.g., 5 mins x $0.22 = $1.10) you should see everything works out. The session times all appear to be rounded to the nearest minute so that might be where the error is in total power delivered to the vehicle. Some of it can also be due to the inherent charging losses as not all of the energy being delivered by the Supercharger gets into the HV battery.
The app probably should show each cost-of-charging-time in chronological order, not by cost rate. In other words, the $1.15/rate should be displayed first in the list as that is what's happening during the charging session; the highest cost/min is at the start of charging and the lowest cost/min is at the end.
ucmndd
Well-Known Member
It’s not clear to me what specific discrepancy or grievance you’re pointing out, but as Ray mentioned, you’re being charged per minute according to the max power level being delivered.
Some states (Wisconsin apparently) don’t allow anyone other than utility companies to charge for power by energy unit (kWh). In those areas Tesla has no choice but to charge by the minute.
Some states (Wisconsin apparently) don’t allow anyone other than utility companies to charge for power by energy unit (kWh). In those areas Tesla has no choice but to charge by the minute.
I went back and pulled up a session there from a couple months ago and it is similarly off. I remember we added 30% there though which would be about 21 kWh not the 12 the session report lists. OP I think the energy delivered numbers are just wrong. In each case its reporting the total # of minutes billed instead of total energy.
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Thanks for the explanation, that makes sense now but still something very different to what I heard about supercharger prices which are usually charged per Kw
Is it normal for the battery range goes down to almost 2/3 when the temperatures are about 45F? I preconditioned the battery before leaving home.
Colder temps do reduce range and higher speed reduces it also. Getting 2/3 rated range driving I94 at the speed limit in 45 degrees sounds about right. Fortunately there are now several superchargers between Madison and the Twin cities so it’s an easy route even when it’s much colder.
ucmndd
Well-Known Member
Be mindful of the distinction between kilowatts (kw) and kilowatt-hours (kWh).
Kilowatts are a measure of power - work over time. A supercharging station can deliver up to 250 kilowatts of instantaneous power. A 100 watt light bulb consumes 100 watts of power whenever the light is on.
Kilowatt hours are a measure of stored energy (potential power). For example, if you charge your battery continuously at 100 kilowatts of power for an hour, you will end up with 100 kilowatt hours of energy in the battery (ignoring losses etc). A 100 watt light bulb left on for an hour consumes 100 watt-hours of energy.
MOST supercharger stations bill by units of energy - $0.xx per kWh. This is the fairest and most straightforward way to do it.
However, as I said above, they are prohibited by law from billing this way in certain locales. When that’s the case they bill by the minute and have different tiers of billing based on how much power is being delivered over that minute. An imperfect approximation but there aren’t many other options.
Doing the math on your first charge in Lake Delton, you paid about $0.55 per kWh average for the session. That’s up there but not far off from typical rates (at least here in CA).
$0.55/kWh would be very high for the Midwest but I don't think we know how many kWh were actually delivered. It appears the app is mistakenly reporting minutes billed instead of kWh delivered.
Yeah, regarding the minutes-vs-kWhr debate. Here in NJ there was that law that said that only utilities could charge by the energy actually delivered.
A bunch of debates around here eventually revealed why this rule was around. Seems that some landlords were putting meters on their tenants' apartments, then charged exorbitant rates, a la monopoly.
The various states that put that rule in were doing so under the argument of, "So, you want to charge like a monopolistic utility? Great - then you get regulated like a monopolistic utility! Off to the Public Utilities Commission You Go. Now, heh heh, justify those rates, just like the utilities have to."
Never occurred to anybody at the time that there might be an actual need for delivering, well, automobile fuel in units of kW-hr's.
In 2018 in NJ, we had those weird, funky high per-minute rates for high power, lower per-minute rates for medium power, and 'way low per-minute rates for very low power levels. I seem to remember seeing stuff like that in Massachusetts at the time as well.
Nowadays, every state in New England, at least, seems to have ditched the per-minute system and gone for per kW-hr. I vaguely remember that CA, of all places, had some charging stations (not necessarily Tesla) a couple-three years ago that were playing per-minute games, with the intent of rooking various electric vehicle drivers. At which point the CA Bureau of Weights and Measures, of all people, put out a white paper demanding more sanity to the whole process, including:
There has been some speculation that certain vested interests who were anti-ev lobbied in various states against per kW-hr standards, the better to muddy the waters. Now that everybody and their brothers-in-laws are selling EVs these days, well, I suggest you Minnesota types write letters to your elected representatives.
A bunch of debates around here eventually revealed why this rule was around. Seems that some landlords were putting meters on their tenants' apartments, then charged exorbitant rates, a la monopoly.
The various states that put that rule in were doing so under the argument of, "So, you want to charge like a monopolistic utility? Great - then you get regulated like a monopolistic utility! Off to the Public Utilities Commission You Go. Now, heh heh, justify those rates, just like the utilities have to."
Never occurred to anybody at the time that there might be an actual need for delivering, well, automobile fuel in units of kW-hr's.
In 2018 in NJ, we had those weird, funky high per-minute rates for high power, lower per-minute rates for medium power, and 'way low per-minute rates for very low power levels. I seem to remember seeing stuff like that in Massachusetts at the time as well.
Nowadays, every state in New England, at least, seems to have ditched the per-minute system and gone for per kW-hr. I vaguely remember that CA, of all places, had some charging stations (not necessarily Tesla) a couple-three years ago that were playing per-minute games, with the intent of rooking various electric vehicle drivers. At which point the CA Bureau of Weights and Measures, of all people, put out a white paper demanding more sanity to the whole process, including:
- All energy delivered to be charged for in energy units (i.e., kW-hr's, Joules, or something like that).
- A display on the charging stall that very clearly indicated how much this was costing the user, then and there.
There has been some speculation that certain vested interests who were anti-ev lobbied in various states against per kW-hr standards, the better to muddy the waters. Now that everybody and their brothers-in-laws are selling EVs these days, well, I suggest you Minnesota types write letters to your elected representatives.
ucmndd
Well-Known Member
yeah that’s a weird goof, but looks like you’re right. It adds up in all the screen shots shared so far.
FWIW I got similar numbers assuming a very pessimistic charging curve:
(5 minutes * 5kw) + (12 minutes * 60kw) + (8 minutes * 100kw) + (3 minutes * 180kw) = 35kwh
But we're both ignoring losses. Power into the vehicle != energy getting stored in the battery. There's various sources of loss:
- Resistance in the battery and in-car wiring. Some of the energy delivered by the charger directly turns into heat (that's in part why the battery typically reaches around 60 deg C while charging!)
- Power to run the heating and HVAC systems to heat up the battery (consumes 5-6kw) (toward the beginning of the charging session)
- Power to cool the battery (toward the end of the charging session)
Minor comment on this. You know that Monroney sticker? The one that's on the car when one buys it and reports on the W-hr/mile? I was surprised to find out last month that the amount of energy per mile is based upon the energy delivered to the car from the charger. Not what the car self-reports.
So, that takes into account resistive losses from the charger to the car, within the car, within the battery (energy in > energy out), losses in the motor, and all that jazz.
I think that when one looks at the energy screen, some kind of fudge factor is put in there by Tesla so that it all matches up with the Monroney numbers.
I'm not 100% sure about this, but I think that the EPA tests may have the HVAC turned on.
All true but aren’t you charged for energy delivered by the charger not how much ends up in the battery?
Yes, exactly. You're charged for what the charger delivers (energy into battery + losses). The app shows Energy Delivered which doesn't include the losses.
I'm trying to potentially explain why the Energy Delivered is unexpectedly low.
Energy delivered does not include losses? Is there a source of info for that part? Not claiming it’s wrong just curious.
The energy delivered is unexectedly low, because that wasn't the energy delivered... It is a bug as @threeputts noted. Notice how all three of the screenshots posted so far are X KWh hour delivered and then the charging time is always one minute more... It is basically reporting the charging time in both spots instead of telling you the actual delivered energy.
I've got a screenshot from a supercharging session here in Nebraska (another state that bills based on time) from Monday that I'll post tomorrow when I have more time to respond to some of the other posts. I have a fairly good recollection of the battery percentages as well, and will show that the pricing ends up being basically equivalent to neighboring states that are allowed to bill by the KWh. It too shows one minute more for the charging session than KWh delivered.
