How pairing at Supercharging works

[David99]

Most already know, two stalls at Superchargers share one charger. For example 2A and 2B are connected to charger #2 and share it's power.

The way they switch is actually interesting. Superchargers are made from (I believe) 12 smaller chargers that each max out at 12 kW. 3 are always grouped together as they use the three phases from the commercial grid power. When both stalls (that share a charger) are used, the power output can only be switched in groups of 3. So when you arrive and the other car is using all the power, you will get the minimum which is 36 kW. Once the other car tapers down enough you will get another group of three which adds up to 72 kW. The next step is 108 kW.

Here is a graph shows the charge rate at a Supercharger. It started with 36 kW, the switched to 72 kW and after 6 minutes it went up to 108 kW. At that point my battery pack wasn't able to take as high of a rate so the power dropped down gradually as the battery fills up.

BTW, urban Superchargers don't have the issue. They are limited to 72 kW but every stall has it's own dedicated charger.

 

[KArnold]

BTW, urban Superchargers don't have the issue. They are limited to 72 kW but every stall has it's own dedicated charger.

Hmmmm, not sure that is a step in the right direction. At least here in the Midwest where SC's rarely see another car, let alone be concerned about pairing. How do they define "urban"?

 

[RedMS]

Hmmmm, not sure that is a step in the right direction. At least here in the Midwest where SC's rarely see another car, let alone be concerned about pairing. How do they define "urban"?

Urban chargers have a smaller cabinet. They are usually installed in high population urban areas (such as a downtown garage or busy mall)

 

[BerTX]

I sure wish Tesla would come up with some way to mark the stalls with the numbers so that they are visible when there is a car parked in them. We just finished a 2500 mile trip with a hitch-mounted cargo carrier on the back. Most locations there was no problem backing in and still reaching the charge port. One spot was in a very crowded parking area at a hotel, and there was a MX connected when we arrived. There were 4 other stalls, so I lined up and backed into the easiest one. The cable did barely reach with the car backed in as far as possible, so I started charging while we went for lunch. After all that manuvering, I realized I was paired with the only occupied stall -- grrr.

I didn't want to move, so I hoped that the MX was either fully charged (likely at a hotel-located SC) or about to leave, so I just watched the charge rate and sure enough, it went to full power.

It sure would be nice to at least have the numbers on the TOP of the stanchion rather than the bottom...

 

[HankLloydRight]

It sure would be nice to at least have the numbers on the TOP of the stanchion rather than the bottom...

Totally! I've also been saying for years that the "A" or "B" is meaningless to owners/drivers, so they should discard that labeling scheme, and just put big "1" or "2" etc at the TOP of each stall. Leave the A/B there for the technicians who need to know which is which.

I've also been saying scrap the numbers all together (you can tell the SC numbering scheme was designed by an engineer).. and just go with colors or some other highly visible indicator.. so when pulling into a location, you can easily avoid pulling into a stall color where there's already someone charging.. i.e. look for a color with two empty stalls, and use one of those for maximum charging rate.

@David99 -- great post, thanks. Makes me wonder what's happening when people report a stall charging at 50kw-60kw (which has happened to me several times recently). Maybe a broken single charging unit in the stack.

 

[TMeister]

...At that point my battery pack wasn't able to take as high of a rate so the power dropped down gradually as the battery fills up.

Curiously, your power curve drops quickly even with SOC only in the 20's. Was the pack cold? I usually maintain 116 kW well into the 50% SOC area.

 

[TexasEV]

Curiously, your power curve drops quickly even with SOC only in the 20's. Was the pack cold? I usually maintain 116 kW well into the 50% SOC area.

You have a 100D and he has a 85.

 

[TMeister]

You have a 100D and he has a 85.

Good point!

Gotta remember to read the fine print...

 

[David99]

I totally agree the marking on the Superchargers is terrible. I think a simple 3 color light on top of each pedestal would help a lot. Red means below 36 kW, orange means up to 72 kW and green means full power available. Or the car could show the stall that is unshared on the screen. Or even just one light indicating unshared.

But honestly the whole sharing thing is not cutting it any more. All the newer cars maintain a pretty high rate for a long time. The 90, 100 and Model 3 all are charging at 90 kW or higher for the bulk of the charge you need on a road trip from station to station.

Annoying having to look at the tiny numbers which is hard during the day and impossible at night. And you never know. Sometimes they are A1 B1 C1 D1 A2 B2 C2 D2 or they are A1 A2 B1 B2 ... And if they are both sides of an aisle, you have no clue.
Driving here in California Superchargers are mostly so full that you take whatever is free and you end up spending more time charging.

 

[HankLloydRight]

Red means below 36 kW, orange means up to 72 kW and green means full power available

That sounds so simple.. it boggles the mind why they haven't done anything like this, or as we suggest, just making the stall numbers easier to see without walking up and down the entire row to figure it out.

 

[Lasttoy]

I went to over 20 states last year. Up and down 95, i always have to explain the pairing.

 

[Gadgetboyea]

Thanks for sharing. Yesterday I was charging in Silverthorne and only a couple spots were open so I parked at the end of the line. I left to get lunch and 20 minutes in the charge stopped with a error. When I returned to the car all the other cars were gone and the charge ring was red. The error on my screen showed an error with the charger. I moved to a different spot and the car started charging normally. I wonder if when the others left, I saw the same spike as in your graph that would cause my car to stop charging.

 

[jlv1]

I've also been saying scrap the numbers all together (you can tell the SC numbering scheme was designed by an engineer).. and just go with colors or some other highly visible indicator.. so when pulling into a location, you can easily avoid pulling into a stall color where there's already someone charging.. i.e. look for a color with two empty stalls, and use one of those for maximum charging rate.

You need to think how this would scale to stations where there are 20 or 40 SCs. Numbered is just simple.

 

[David99]

You need to think how this would scale to stations where there are 20 or 40 SCs. Numbered is just simple.

The paring thing is something Tesla doesn't like to talk about much because it is a limitation and inconvenience. They doesn't like to point that out. That's why I doubt that they will implement any system that would show which stalls are shared. The only real solution is to either increase the total power rate per charger so that even what two cars are charging simultaneously, both cars get a decent enough rate. Or do the same they do with the urban Superchargers, each stall has a dedicated charger. Just not limited to 72 kW but at least 108 or more

 

[PaulusdB]

That sounds so simple.. it boggles the mind why they haven't done anything like this, or as we suggest, just making the stall numbers easier to see without walking up and down the entire row to figure it out.

I'm afraid there are very mundane reasons for this type of ‘unlucky’ design choices. For starters it's all just-in-time designed and build, introducing trial-and-error processes later on. Then there are the (original) designers that have never seen a EV or used an EV-charger to begin with. Finally I suspect some obscurity attempts, trying to hide the limitations of the charging infrastructure and process.

Another example of such unlucky design choices is the indicator for mph charging speed that averages over the full session. That way it shows higher 'speeds’ but encourages the user to keep on charging to an higher SoC.

 

[Uncle Paul]

I believe the current marking scheme makes perfect sense.

They need to number all the chargers, so people can report which one might be sub par. Also technicians need to know which one needs looking after. Contacting Tesla, an arriving customer can be ask which of the chargers gives the fastest charging.

The A-B label quickly shows arrivals which non paired slot might give them a full charge.

Might be better if the A-B label was mounted higher up on the device to make it easier to see, but that would not look quite as good from a design stand point.

 

[Rocky_H]

People always suggest using colors, and then people always have to remind them that some people are color blind. The numbers and letters are good, but at the top instead of bottom would certainly be easier to see.

 

[David99]

Curiously, your power curve drops quickly even with SOC only in the 20's. Was the pack cold? I usually maintain 116 kW well into the 50% SOC area.

I have an old 85 D pack. They peak at very low state of charge, keep the peak rate only until 15-18%, then they drop continuously. At 50% you get around 60 kW. That's how the first generation cells worked. The newer cells are different. They can hold a pretty high rate up to 50% or even more. They are just better at taking the high rate charge. The only small advantage the old cells have is when the pack is at 0% they start charging at peak rate within one minute. The new cells can't charge that fast when they are very low. They have to slowly ramp up and reach the peak at around 10%. But then they hold that much longer. For example from 10% to 70% a Model 3 charges almost twice as fast as the old 85 packs at the same Supercharger.

 

[David99]

The A-B label quickly shows arrivals which non paired slot might give them a full charge.

Depending on the location it's pretty hard to see. If a few cars are charging, you can hardly see the numbers looking between the cars. Some locations have the cabinet in the middle and stalls left and right and all A stalls are on one side then all B on the other. You have to drive back and forth and try to peak between cars. nose in stalls are even worse. The labels are on the sides and when a car is parked the number is blocked by the car.

I supercharged 900 times in the last 4 years visiting 100 different superchargers. It was not an issue at all in the beginning. But in the last year or so superchargers have become busy and it becomes more and more of an issue.

 

[The Duke]

I have a few guesses here. The numbers are not for us, they are for the maintenance people. Pairing allows for an easy upgrade path when faster charging is needed. We were never supposed to figure all this out.

OP, nice post!