SageBrush
REJECT Fascism
They do not. If fact the power draw differs by ~ 4.5x.
Do you still want to hold on to your opinion ?
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California bans per-minute billing; Tesla Superchargers will need displays
- Thread starter FlatSix911
- Start date
Do you still want to hold on to your opinion ?
Huh? The difference between 20% and 40% is 20% of the battery's total capacity, and the difference between 80% and 100% is also 20% of the battery's total capacity. The total amount of power delivered (in kWh) is exactly the same, even if it was delivered at a different rate (ignoring minor differences in power because of things like the car's computer and heat/air conditioning drawing power for 35 minutes instead of 8 minutes).
SageBrush
REJECT Fascism
No, I'm not. This is basic first-year algebra:
(.4x - .2x) = (x - .8x)
for any value of x.
I think some people are hinting at the difference between power and energy. @dgatwood you are talking about energy delivered. That is approximately the same (ignoring some losses). However in the one case it delivered over a longer period of time, this means less power was needed to do it. This might help: Energy vs power - Energy Education
Kiwiadventure
Member
Power is fuel and law has always been there. It's the providers of these chargers who decided to not comply with the law.
I see your point, but you're ignoring the difference between how much energy the station is putting out and how much energy is actually stored in the battery. Not only is there charging efficiency due to I^2R losses in the cabling, but electro-chemical losses in the battery charging conversion to ions, but also, the bigger effect, is accessory consumption like pumps and heating and A/C that is consuming power from the charging station that is not even trying to charge the battery. Tesla is just now starting to base their Supercharger accounting on station output instead of stored energy. I think this change is a result of the kind of ruling described in this thread. They need to charge based on station output, so they're starting to do that now.
Good article... thanks for sharing.
Power is how fast energy is used or transmitted - power is the amount of energy divided by the time it took to use the energy. Its unit is the watt, which is one joule per second of energy used. A circular saw will draw a certain amount of power to run, and how quickly power is drawn from a battery determines how long its stored energy will last.
- P is the average power output, measured in watts (W)
- ΔEsys is the net change in energy of the system in joules (J) - also known as work.
- Δt is the duration - how long the energy use takes - measured in seconds (s)
This is why a kilowatt is a unit of power but a kilowatt-hour (1 kilowatt times 1 hour) is a unit of energy.
Get ready for the next money grab by the state of California... once the kWh metering is ready, a fuel tax will be added shortly after.
Ouch. I wonder how “free supercharging” will work if that happens.
Buddy
Member
My house uses electricity but the meter doesnt show charges... hows that different?
Your house meter is not a "fuel dispenser". Requirements on an electric utility and a EV charging provider are necessarily different.
I'm not a big govt person, but I do figure that one of the roles of government is to facilitate competition be providing a level playing field where consumers can easily compare prices. Left entirely on their own, oligopolistic sellers of certain commodities (think cell phone service) will be very creative in obfuscating their pricing with complex schemes that prevent buyers from easily comparing prices, with the net result that prices are higher than they otherwise be.
You can easily see that the vehicle charging stations will become a natural oligopoly or monopoly, likely owned by the power utilities. And therefore it will have to be regulated anyway.
Yes, the charge efficiency does vary based on state of charge, but the average charge efficiency is a whopping 99%, so it's noise. And if the losses in the cabling were significant, the hardware would overheat and damage itself, so we can safely assume that's noise, too. So maybe the faster charging results in using a few percent more total power delivered. That is, of course, balanced out by having to power the heater for a longer period of time if you charge more slowly (which I'm pretty sure I mentioned specifically), so it is likely a wash, give or take.
Either way, the point is that when one person is using a charger, nobody else can use that charger, so there's a very real opportunity cost involved every time you allow a vehicle to charge from 80% to 100% SoC, when you could otherwise allow two vehicles to go from 20% to 80% in that same time slice, and any billing scheme that doesn't factor that in at all is likely to encourage people to behave in ways that are detrimental to charger availability.
Yeah, sorry. I was being sloppy with my terminology there. I meant power in the vernacular sense.
SageBrush
REJECT Fascism
Indeed, and it matters.
Differences in power is the main determinant of the vendor's cost to deliver a charge to your car. When you ignore that fact, the value of your opinions suffer because they ignore reality. I understand your POV as a consumer who wants unfettered access to charging but try to understand the other sides to this matter.
You are, I assume, talking about capacity costs. And you’re right that having more peak power means a higher cost per kW. But what you’re missing is that those costs are calculated based on peak utilization over an entire month, which means those costs aren’t going to go down just because some percentage of people charge at a slower rate. You would have to cap *everyone* at a slower rate (or at least cap the total). In other words, that is effectively a sunk cost.
So either way, your per-kWh cost is fixed, and your equipment depreciation and site lease costs per month are fixed, but are spread across the number of kWh that you resell, which means it costs Tesla more per kWh, assuming all else is equal, if a customer is charging more slowly, than for a customer at that same charger who is charging at a faster rate.
SageBrush
REJECT Fascism
I'm talking about demand charges. They are charged based on the highest 15 minute load in a month which is why power draw is such an important cost determinant.
They DO NOT change the cost per kW; the demand charges are proportional to peak power.
Would you please get a clue.
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Interesting reading... https://electrek.co/2020/01/15/tesla-home-charging-station-wifi-connection-design/
Demand charges are the consumer term for what I was talking about. So let me explain this a second time in a different way so that perhaps you will understand why you are provably, obviously, and inarguably objectively wrong.
If you have even one single fifteen-minute period within the entire month in which the supercharger is running at maximum capacity, your demand cost is set by that period.
So no matter how slowly anybody else charges during that entire month, that charge is not going to change.
So the cost per kWh does not depend in any meaningful way on whether any single car is charging at a slower rate unless the charging station is chronically underutilized and never reaches peak power draw. Thus, there is no savings to Tesla for drawing less power during any arbitrarily chosen charging session other than the lower cost from buying fewer kWh.
And the cost of equipment is constant, which means that it depreciates at a constant dollar figure per month, and the cost of leasing the parking space under it costs a fixes dollar amount per month. So for any given charging station, assuming that they do not upgrade or downgrade the equipment in a way that would change the maximum power draw (peak usage), Tesla makes more money if cars spend less time per stall, because their fixed costs (rent and equipment) are divided over more kWh resold. That likely means you pay less per kWh if people spend less time charging, too.
SageBrush
REJECT Fascism
No.
Capacity charges are based on energy consumption over a month to a year time scale.
Demand charges are typically based on energy consumption over 15, but sometimes 30 minute intervals.
The highest demand at the location (that lasts 15 minutes) sets the demand charges for the month.
So once again: the kWh charges to the vendor are proportional to the total energy delivered;
while the demand charges are calculated based on the highest load during any 15 minute period during the month.
Earlier you said
What you are failing to understand is that the vendor has demand charges that it has to decide how to apportion. Demand charges vary by location but my experience is $10 - $20 a kW. So that first Model 3 that charged at 200 kW for 15 minutes minutes has added somewhere in the range of $2,500 - $5,000 of cost to the monthly bill. Eight charger stall ? Up to $40,000 of monthly demand charges.
Lets try a little arithmetic for a location with expensive demand charges:
There are 730 hours in a month. A fairly busy location might have 1/3 overall capacity use, meaning plug in the car so 730/3 = 243 hours. If the vendor tries to spread out the demand charges by plug time, the car owner is charged $5,000/243 = $20.5 an hour + volumetric charges.
How about a location with peaky use but overall 10% of time plugs are in cars ? Now the demand charges are covered by evenly billing every car owner ~ $1 a minute + volumetric charges.
It should not be too difficult for you to grasp that the 50 kW car owner would find these time based demand charges exorbitant since it would work out to well over $1/kWh for them. And yet you want to charge the slower charging car *more* because it might get in your way.
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