UPDATED: 'How it works' - SuperCharger Station

UPDATED: 'How it works' - SuperCharger Station

For your info, here's how a typical (in this case the Port St Lucie, FL) supercharger infrastructure is configured:

The eight bay setup takes a 12kV, 750kVA feed from the utility, steps it down to 480V three phase on site, pushes that into 2000A switchgear which feeds four (one for each pair of bays) SuperCharger units at 480V/200A. Each unit contains 12 [Model S] 10kW rectifiers for 120kW.

For safety reasons the 'pod' that the car plugs into is not energized until the cable has done a handshake, so if something accidentally flattens a pod or the cable is cut there is no danger.

Each unit is 120kW and will load balance between two bays - if two cars are at the same SOC they'll each get 60kW, whereas if one is empty and one is close to full it will split it 90/30. So...if you come into an SC station and there are several empty bays DO NOT park next to an existing car unless you first check the label on the SC - each one should be labeled 1A, 1B, 2A, 2B, etc. Avoid taking the same number if you can so you get the full 120kW.

Strictly speaking all old SCs are only 90kW, but are being upgraded. All new SCs are 120kW but will only push 90kW right now because the cars require a firmware update to take 120kW, and a tweak is needed at the SC station. No date on when the change is going to happen.

Tesla is exploring pushing the units to 150kW in the future.

Update: I forgot to add - to accelerate the build out SCs are being built without solar and without the 'spaceship' signage. Both are over 10' tall and therefore have additional zoning restrictions that delay the permitting process. Tesla is committed to getting the SCs out as fast, far and wide as possible and is currently limited by the permitting process. They are therefore doing everything to speed that part of the process up. At some point in the future when some unspecified criteria are met, TM will begin the process to add solar and signage to some/all (?) of the SCs.

agiangone | 24 July 2013

Very interesting and useful. Thanks

Kleist | 24 July 2013

Thanks & big cheers from CA for your first SC

Robert22 | 24 July 2013

Thanks Nick.

If you're at the Milford CT supercharger as I was last weekend, you can watch load balancing in action. There are only two cables both north and southbound. Didn't mind the delay however as the other Tesla owners were quite interesting :)

NomoDinos | 24 July 2013

Great info. Thanks Nick

ian | 24 July 2013

Really great info! Thanks for sharing.

Curious how they will push it up to 150. Will they need new hardware since the current SC's are 120?

Congrats on the SC's!


ian | 24 July 2013

Sorry for the multiple posts but I asked that question above before letting all that info sink in. ;-)

I guess I can answer that myself. Correct me if I'm wrong though.

So it sounds like they'll need to add 3 more of the 10kW chargers per unit. I assume from some of the pictures I've seen that they have left extra space in each cabinet for more chargers so they can just drop them in.

Tâm | 25 July 2013

Thanks nickjhowe.

Should the Ampere be 255 instead of 200?

I've seen the reading on my car's charging screen:

Amperes Input = as high as 248

Amperes Available = 255

Updates 4.5 and later no longer show Available Amperes.

nickjhowe | 25 July 2013

I'm quoting what I heard, so maybe the 200 was a mis-statement if there's hard evidence of higher current

I believe another 3 rectifiers would be needed; we weren't allowed to see in the cabinets - all the SCs were powered up there v. dangerous - so don't know how much room they have in them.

nwdiver93 | 25 July 2013

Don't recall the specific source... Might have actually been Elon @ TESLIVE but all new SCs should be 120 kW but the cars need a software update to charge @ 120 vs 90. I suppose the greatest advantage until that update is two cars on the same SC can charge @ 60kW each instead of 45...

jkirkebo | 25 July 2013

Nope, they can charge at 60kW each today as all SCs have 12*10kW chargers. The difference is with 120kW charging one car can take all the juice for itself. Today 90kW is max so at least 30kW is always available on the second port.

nickjhowe | 25 July 2013

@nwdiver - per my OP at the top of this thread: "Strictly speaking all old SCs are only 90kW, but are being upgraded. All new SCs are 120kW but will only push 90kW right now because the cars require a firmware update to take 120kW, and a tweak is needed at the SC station. No date on when the change is going to happen."

Tâm | 25 July 2013

Great info nickjhowe!

Thanks for the explanation.

I found my picture of 247 Amperes going in, out of 255 available Amperes at 362 Volts and at the rate of 90kW and so far 2kWh has gone in my car at that time:

Koz | 27 July 2013

Did they say how efficient the rectifiers are? I would guess from car charging efficiencies that it is low 90's. That is a high heat rate at full load (@10kw). Do they have fans in the Supercharger units or is cooling passive? With 100+ degree ambient that means some high temps. Are the external surfaces thermally insulated?

Davidinkl | 27 July 2013

@nickjhowe. I've seen inside the cabinets and I saw no extra room for 3 more chargers.

I didn't see any active cooling, but there might have been some behind the units. IMO Tesla will push all the chargers beyond 10kW to get the 150kW. More than likely it is an over temperature limitation not circuit design.

shop | 27 July 2013

The early Harris ranch one had big loud fans. Don't know about the latest designs. | 27 July 2013

Thanks Nick

O EMSHN | 27 July 2013

I was at Atascadero and Buellton last week and didn't see the numbering on the eight bays (1a, 2a, 1b, 2b, etc). I didn't look real hard since I was the only one there. Gilroy is numbered clearly.

tes-s | 25 August 2013

Thanks! That explains why I am not seeing the full 200 miles/half hour in the 120kw Darien SC.

While the new 120 SCs are not turned up yet, do you think they will deliver 60 each if two cars are charging, or is the total limited to 90kw?

dortor | 25 August 2013

I've heard 60 more than 120 total...

nickjhowe | 25 August 2013

Can't remember exactly what Tesla said about the current firmware, but with the new firmware the power delivered to each car in a pair depends on each battery's state of charge. If they both have a similar SOC they'll each get 60kW. If one is close to empty and the other is close to full, the empty one will ket much more (90:30?) than the other. Basically the SC will load balance across the two cars based on SOC.

I ** think ** that with the current 90kW firmware it just splits in half, but I could be wrong.

mdemetri | 25 August 2013

I believe (but not certain) that there is also a time component, so that the car that started charging first gets more of the capacity than a newly arrived car, regardless of the SOC. This is my experience at the SC's in CA but I cannot put precise numbers on the relative amount delivered to the two cars.

mdemetri | 25 August 2013

One clarification, once the first car gets close to full charge and the amps start to decrease, this will then get transferred to the second car.

AirForce462 | 26 August 2013

I used to build and do the final burn in of the Superchargers, when I was employed at Tesla. There is no room in the cabinet's for extra chargers so if they are planning on increasing the output of the SC then it will likely entail an rebuild of the units. There is an active cooling fan on the SC's, you cant miss them they are loud and located on the back of the units under a hood.

danej | 26 August 2013

What's "SOC" mean?

shs | 26 August 2013

State Of Charge

lolachampcar | 26 August 2013

Thanks Jason...

Would you care to comment on the hand shaking between the SC and MS? I assume there is some sort of authentication that prevents unauthorized use.

AirForce462 | 26 August 2013


Not too sure about firmware handshaking as this was not part of my purview. I assume that the SC chats with the BMB's (Battery Monitoring Boards) to determine state of charge, and if there were a communication fault (e.g. not a tesla battery pack) that no charge state would begin. I wish that I could be more helpful but my experience was limited to the information necessary to perform my functions.

lolachampcar | 26 August 2013


tes-s | 26 August 2013

My vote is for the first car to get whatever juice it would get if the companion stall were empty. Second car gets the leftovers, with the idea that the first car will reach a taper point and begin drawing less, making more available to the second.

I think that is optimal - get each car out as quickly as possible.

dedood | 2 September 2013

Note: when a station is in use, pick a different LETTER, not a different NUMBER. They are grouped by letter, NOT number (1a, 2a) (1b, 2b). I was just at the Fremont super charger, and other was a car in 1A, and I was in 2B. A new car pulled up and went into 2A, thinking that since I was about to leave, she would not share with 1A. However, when I stopped, her rate stayed low, but when 1A disconnected, she immediately jumped up. So, avoid being next to another car, and stay away from the same LETTER.

nickjhowe | 3 September 2013

@dedood - this is a problem. Looks like Tesla is inconsistent with their numbering schemes. At Port St Lucie it is definitely (1a, 1b), (2a, 2b)

Let me check with my contact and see if we can get to the bottom of this.

hsadler | 3 September 2013

I think a fix for that situation has been mentioned. If rate doesn't change - unplug and re-plug to begin the session again. Then the rate should go to maximum if the partner slot is unoccupied.

nickjhowe | 3 September 2013

@dedood - I've had it confirmed from the Tesla exec responsible for the supercharger build out that same numbered posts are on the same supercharger. (1a, 1b) (2a, 2b) etc. Therefore the original instructions stand - avoid using the same number as another car if you can.

His only guess was that the jump you saw was coincidence with something else happening.

NKYTA | 3 September 2013

@nick, thanks for checking!
I thought I was going to have to re-imprint new info; it doesn't always work. ;-)

cerjor | 3 September 2013

I arrive at an SC with 50 miles left and need to charge to 230 rated miles. For minimum charging time should I set the car to maximum charge (265 rated miles) and stop at 230 miles or set the car at 230 rated miles and wait for charging to complete?

nickjhowe | 3 September 2013

@cerjor - based on what I've seen the charge rate is a function of SOC, not target charge level. So if you come in with 50 miles, the car should charge at the same rate whether you set your target as 50%, 90% or 100%. I don't think the car will artificially slow down as you get close to the 230 target - it should keep charging as though it were going to 265, then just cut off.

But this is only an assumption based on my best understanding.