How pairing at Supercharging works

[dark cloud]

You were only frustrating yourself. If you pull into a paired stall, plugging in won't affect the other car that was there first. You'll only be limiting your charge rate.

Unless he *ahem* does the rudest thing you can do at a supercharger, but it is better left unsaid.

 

[Rocky_H]

You were only frustrating yourself. If you pull into a paired stall, plugging in won't affect the other car that was there first. You'll only be limiting your charge rate.

Not entirely true. There is a priority, but the secondary car does have a guaranteed minimum level, not just leftover scraps. So on the slightly older ones that are 120kW total power to the two stalls, the secondary car gets 30kW minimum, and that can lower the primary car to 90kW, even if they are at a low state of charge and would have been able to take more than 90kW.

 

[HankLloydRight]

Ok, but the chances of that are pretty small, and even then the first car may only very slightly inconvenienced.

 

[Rocky_H]

Ok, but the chances of that are pretty small, and even then the first car may only very slightly inconvenienced.

Of course the scenario would be a bit rare, but it's good to inform when people are making absolute statements that aren't always true, like "won't affect the other car".

 

[TexasEV]

How many sites still have 120 kW chargers anyway? I thought most if not all were upgraded to 135 kW.

 

[Rocky_H]

How many sites still have 120 kW chargers anyway?

Lots.

I thought most if not all were upgraded to 135 kW.

I've never heard of them upgrading any of the 120kW ones at all, and there are still a lot of them out there. The 90kW ones did all get upgraded, which made sense, because that wouldn't even support full power for one car. But I think they've left the 120kW ones alone, but at some point they switched over on new installations putting in the 135kW instead of 120kW.

 

[israndy]

Unless he *ahem* does the rudest thing you can do at a supercharger, but it is better left unsaid.

Do you mean: Tesla Supercharger Manners a Work in Progress

-Randy

 

[MorrisonHiker]

Do you mean: Tesla Supercharger Manners a Work in Progress

-Randy

That's rude but not the unspoken rudeness that @dark cloud was referring to, I don't think.

 

[Saghost]

That's rude but not the unspoken rudeness that @dark cloud was referring to, I don't think.

Nope. It's unethical, but there is a way to... ...change... the priority order of the two cars sharing a charger stack.

 

[israndy]

Oh, Somehow I thought we were talking about something grosser, but it is still of interest.

Wasn't there an issue with starting and stopping charging that allowed users to skip paying? Bringing issues like those to light instead of not talking about them means the company can take positive steps to fix them.

-Randy

 

[BerTX]

Do you mean: Tesla Supercharger Manners a Work in Progress

-Randy

I park like that when necessary. Some Superchargers are stupidly configured and do not give the driver any other choice if they have hitch-mounted cargo. If the charger is in the middle of nowhere and nobody is there, I try to minimize the impact. If it looks like the stalls might be needed, a driver stays with the car at all times.

In most cases, it is just the positioning of the signs that is the problem. If they installed the signs a foot or so farther from the curb, it would allow backing in with cargo attached.

 

[Rocky_H]

Wasn't there an issue with starting and stopping charging that allowed users to skip paying?

I've never heard of anything that can get around the paying.

Nope. It's unethical, but there is a way to... ...change... the priority order of the two cars sharing a charger stack.

Yeah, that's the one.

Bringing issues like those to light instead of not talking about them means the company can take positive steps to fix them.

They've been told about it and known of it for years, so they seem to have no intention of fixing it. Which brings us to this: It's such a dick move, and Tesla isn't going to fix it, so it's better to have as few people as possible know about how to do it.

 

[gnuarm]

It is 72 kW, not 73. 72 / 12 = 6.
Supercharger sites are fed by 3 phase power. Three chargers always act as a group to ensure all three phases are used equally. the max total of 144 kW comes from 4 groups (of each 3 chargers). 4 x 3 x 12 kW = 144 kW. 120 is the maximum per stall probably limited by switches / wire / breaker size. Urban chargers are 72 kW per stall. Again, two stalls are fed from one cabinet so the total is 144 kW.

You misunderstand. A vehicle charges at a power level as determined by the car not necessarily the maximum the chargers can provide. So go back and read my post again with the correct understanding.

The issue has nothing to do with three phase power. The issue is that there are only enough power converters for a total of 144 kW. If a car is not drawing the maximum of the charges it is using the remainder is not used. So for any given arrangement there are two cars which may both not be drawing the full amount of the chargers they are on resulting in an apparent shortfall of many kW.

It's sometimes the limitations found at a specific site and a matter of cost to avoid hefty peak demand charges. As mentioned, it is much better to divide the total power up to more stalls. 12 car charging at a slightly reduced rate is better than 8 car charging and 4 waiting in line getting frustrated and posting about it on social media. It is much preferable to be able to plug in and getting a coffee rather than having to wait in line. Even when all stalls are in use, there is a chance all of them combined are not reaching the max power. Two cars at a pair could be at a high SoC and thus not use the full power available. By having more stalls this extra power could charge more cars even if they are not getting the full power they could take. Also keep in mind, if you wait in line and then charge faster, you spend just as much time overall, than when you plug in and charge at a slower rate. Except it is much better to be able to plug in and do other things.

None of this is in line with the facts. A commercial operation is billed based on peak usage. But for car charging that is not going to be the dramatic difference seen when starting an electric motor. I am sure electric rates have little to do with limiting power to the cars.

Charging rate is something that needs to be predictable. Just as it will never be acceptable to wait in line to charge (not to mention creating congestion in a public parking area) users need to be able to plan their lives. If they are on a trip, having to charge for an hour is bad enough, having to wait longer because the car won't charge at full rate for no apparent reason is equally unacceptable.

 

[hiroshiy]

You misunderstand. A vehicle charges at a power level as determined by the car not necessarily the maximum the chargers can provide. So go back and read my post again with the correct understanding.

The issue has nothing to do with three phase power. The issue is that there are only enough power converters for a total of 144 kW. If a car is not drawing the maximum of the charges it is using the remainder is not used. So for any given arrangement there are two cars which may both not be drawing the full amount of the chargers they are on resulting in an apparent shortfall of many kW.




None of this is in line with the facts. A commercial operation is billed based on peak usage. But for car charging that is not going to be the dramatic difference seen when starting an electric motor. I am sure electric rates have little to do with limiting power to the cars.

Charging rate is something that needs to be predictable. Just as it will never be acceptable to wait in line to charge (not to mention creating congestion in a public parking area) users need to be able to plan their lives. If they are on a trip, having to charge for an hour is bad enough, having to wait longer because the car won't charge at full rate for no apparent reason is equally unacceptable.

I think you need to check two cars charging at the same time, at paired stalls. You will see what @David99 is talking about. The charger power is not changing in 12kW steps, rather, it changes in 36kW steps. Your point about wasting charger remaining power is valid. That's why urban chargers are created - they just reduce waste and increase total throughput in very crowded situations.

Re; demand charges, it's not cheap. In fact, at least in Japan demand charges is the biggest reason to cap the total charging site power.

For example, in Tokyo;
業務用電力（契約電力500kW未満）｜電気料金プラン　高圧・特別高圧｜東京電力エナジーパートナー株式会社
Less than 500kW contract. 15.5 USD per kW of demand charges. That means with 135kW Tesla superchargers for four stalls, total power 270kW, so 4185 USD. Electricity cost is not included. Large sites like shopping centers and large buildings with superchargers typically have single high voltage feed and single contract, so the owners estimate peak electricity demand (like in summer heat) and try NOT to exceed planned kW, by turning off AC in some areas etc. In Japan superchargers are actually power limited in hotels if the hotel is using too much power on that day.
Many Japanese DCFCs in shopping centers also reduce power in summer.

How many months do you have to keep the demand charges in the US? In Japan it's one year - so once you get to the peak, you keep paying for that peak rate for a year from that date. In the 4185 USD case you need to pay 4185 USD x 12 months = 50220 USD in demand charges annually.

 

[gnuarm]

I think you need to check two cars charging at the same time, at paired stalls. You will see what @David99 is talking about. The charger power is not changing in 12kW steps, rather, it changes in 36kW steps. Your point about wasting charger remaining power is valid. That's why urban chargers are created - they just reduce waste and increase total throughput in very crowded situations.

You aren't getting what I'm saying, that the power doesn't change in large steps at all. The CAR controls how much power is drawn. If the car only draws a small amount, that's what the charger provides.

I don't know that the steps of charger allocation are 36 rather than 12 kW. I have no insight into that. I would like to see the info on how the Superchargers work if anyone has a link for that. My point is that just because the chargers are on 3 phase power does not necessarily imply they have to be ganged in threes. In fact, that would be rather inefficient in that there could be a much larger gap between what the two cars are drawing and the maximum available from the chargers.

Re; demand charges, it's not cheap. In fact, at least in Japan demand charges is the biggest reason to cap the total charging site power.

For example, in Tokyo;
業務用電力（契約電力500kW未満）｜電気料金プラン　高圧・特別高圧｜東京電力エナジーパートナー株式会社
Less than 500kW contract. 15.5 USD per kW of demand charges. That means with 135kW Tesla superchargers for four stalls, total power 270kW, so 4185 USD. Electricity cost is not included. Large sites like shopping centers and large buildings with superchargers typically have single high voltage feed and single contract, so the owners estimate peak electricity demand (like in summer heat) and try NOT to exceed planned kW, by turning off AC in some areas etc. In Japan superchargers are actually power limited in hotels if the hotel is using too much power on that day.
Many Japanese DCFCs in shopping centers also reduce power in summer.

How many months do you have to keep the demand charges in the US? In Japan it's one year - so once you get to the peak, you keep paying for that peak rate for a year from that date. In the 4185 USD case you need to pay 4185 USD x 12 months = 50220 USD in demand charges annually.

Can't say I follow all the details of how they charge for electricity in Japan. What I know is failing to provide adequate current to charge cars would be very bad PR. The only "gotcha" I Know of here is the peak usage charges which, as I said before, are an issue for loads that have high variation like motors. They have significant surge currents when first turned on. A friend who worked at a processing plant would try to get them to start the motors one at a time to avoid the motor surges all happening at the same time. It would make much less sense to shut motors down entirely to reduce the peak further. That is analogous to what you are suggesting that Tesla would install Superchargers but not allow them to run at full rate when the stalls are all full. As I said, very bad press. The Superchargers are the most prevalent projection of Tesla's presence other than the cars themselves. It would be a very damaging thing to have them turn into problems for the users and have that be public knowledge.

 

[Saghost]

I think you need to check two cars charging at the same time, at paired stalls. You will see what @David99 is talking about. The charger power is not changing in 12kW steps, rather, it changes in 36kW steps. Your point about wasting charger remaining power is valid. That's why urban chargers are created - they just reduce waste and increase total throughput in very crowded situations.

Re; demand charges, it's not cheap. In fact, at least in Japan demand charges is the biggest reason to cap the total charging site power.

For example, in Tokyo;
業務用電力（契約電力500kW未満）｜電気料金プラン　高圧・特別高圧｜東京電力エナジーパートナー株式会社
Less than 500kW contract. 15.5 USD per kW of demand charges. That means with 135kW Tesla superchargers for four stalls, total power 270kW, so 4185 USD. Electricity cost is not included. Large sites like shopping centers and large buildings with superchargers typically have single high voltage feed and single contract, so the owners estimate peak electricity demand (like in summer heat) and try NOT to exceed planned kW, by turning off AC in some areas etc. In Japan superchargers are actually power limited in hotels if the hotel is using too much power on that day.
Many Japanese DCFCs in shopping centers also reduce power in summer.

How many months do you have to keep the demand charges in the US? In Japan it's one year - so once you get to the peak, you keep paying for that peak rate for a year from that date. In the 4185 USD case you need to pay 4185 USD x 12 months = 50220 USD in demand charges annually.

I don't know where you got the idea, but I do not believe there is any circumstance where the urban charger delivers more total power to cars than the sharing Superchargers, and there are a lot of circumstances where it delivers less.

Think about it: the sharing system always has the option of a fifty fifty split, and will use it when appropriate, but the urban system can never give a car more than 72 kW, even if there's no car on the other side or the other car is at the top of the taper and can't use the power.

What the Urban charger gives is a more predictable (but on average slower) first five/ten minutes, and a smaller gauge wire and/or longer wiring runs from charger to stall.

 

[gnuarm]

I don't know where you got the idea, but I do not believe there is any circumstance where the urban charger delivers more total power to cars than the sharing Superchargers, and there are a lot of circumstances where it delivers less.

Think about it: the sharing system always has the option of a fifty fifty split, and will use it when appropriate, but the urban system can never give a car more than 72 kW, even if there's no car on the other side or the other car is at the top of the taper and can't use the power.

What the Urban charger gives is a more predictable (but on average slower) first five/ten minutes, and a smaller gauge wire and/or longer wiring runs from charger to stall.

I expect there may be lower equipment costs... well, some anyway. The circuitry to switch charger units between stalls can be left out.

Still, I'm not seeing the reasoning behind the urban chargers. I guess it all comes down to charging rate predictability. When the stalls are more than half full the flexible chargers can greatly increase the charge time of the "second" cars. They are a better idea when the stalls are often sparsely occupied. I just can't see the cost varying enough to matter.

 

[hiroshiy]

You aren't getting what I'm saying, that the power doesn't change in large steps at all. The CAR controls how much power is drawn. If the car only draws a small amount, that's what the charger provides.

I don't know that the steps of charger allocation are 36 rather than 12 kW. I have no insight into that. I would like to see the info on how the Superchargers work if anyone has a link for that. My point is that just because the chargers are on 3 phase power does not necessarily imply they have to be ganged in threes. In fact, that would be rather inefficient in that there could be a much larger gap between what the two cars are drawing and the maximum available from the chargers.




Can't say I follow all the details of how they charge for electricity in Japan. What I know is failing to provide adequate current to charge cars would be very bad PR. The only "gotcha" I Know of here is the peak usage charges which, as I said before, are an issue for loads that have high variation like motors. They have significant surge currents when first turned on. A friend who worked at a processing plant would try to get them to start the motors one at a time to avoid the motor surges all happening at the same time. It would make much less sense to shut motors down entirely to reduce the peak further. That is analogous to what you are suggesting that Tesla would install Superchargers but not allow them to run at full rate when the stalls are all full. As I said, very bad press. The Superchargers are the most prevalent projection of Tesla's presence other than the cars themselves. It would be a very damaging thing to have them turn into problems for the users and have that be public knowledge.

Re three phase:

I think I understand your argument. However, please actually try to test it. Prepare two almost empty Teslas and start charging at paired stalls. Then disconnect the first car and see what happens. In very crowded superchargers, you will see exactly what @David99 mentioned.

Re, power limit:
I agree it's a bad press, but it's unfortunately a fact.

 

[hiroshiy]

I don't know where you got the idea, but I do not believe there is any circumstance where the urban charger delivers more total power to cars than the sharing Superchargers, and there are a lot of circumstances where it delivers less.

Think about it: the sharing system always has the option of a fifty fifty split, and will use it when appropriate, but the urban system can never give a car more than 72 kW, even if there's no car on the other side or the other car is at the top of the taper and can't use the power.

What the Urban charger gives is a more predictable (but on average slower) first five/ten minutes, and a smaller gauge wire and/or longer wiring runs from charger to stall.

Consider two stalls of supercharger in urban environment, almost full for several hours. In that case urban superchargers can offer 72kW to 50kW up to 85% battery, so almost running full capacity. On the other hand regular superchargers are like 36kW increments, so if two cars are sharing each takes 72kW (same as urban), but if one car started earlier it takes 108kW giving the other car only 36kW. The problem is that the first car is tapering off - during this time, for example at 100kW, the paired total output is only 136kW, rather than 144kW. Hope this makes sense.

 

[David99]

Consider two stalls of supercharger in urban environment, almost full for several hours. In that case urban superchargers can offer 72kW to 50kW up to 85% battery, so almost running full capacity. On the other hand regular superchargers are like 36kW increments, so if two cars are sharing each takes 72kW (same as urban), but if one car started earlier it takes 108kW giving the other car only 36kW. The problem is that the first car is tapering off - during this time, for example at 100kW, the paired total output is only 136kW, rather than 144kW. Hope this makes sense.

That is actually an interesting thought. Currently Tesla is giving the first car priority. The first car gets as much as it can take even if that means it uses a set of 3 chargers partially. If it charges at 76 kW it uses 6 chargers fully (= 72 kW) plus another set of 3 chargers but only takes 4 kW from those. It meas 32 kW are unused that the second car could use. To maximize power to all cars the supercharger should switch a partially used set of chargers to the second car where it would be used to 100%.