Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

How does a Supercharger work?

This site may earn commission on affiliate links.
I know it is charging DC but how does it get enough power from a typical pole transformer that is shared with other energy users? A 6 bay charger station filled with cars needing a charge, even derated 50% and 100% efficient (which it isn't) would be pulling 360 kW from a distribution transformer that is shared. Since it is DC charging, are they using batteries as a buffer so that they can pull a smaller load for a long time during non use to have say the equivalent of 12 Tesla battery banks charged and ready to dump their charge into the cars?

I just can't find any info on how it is done, could someone point out a link for me?
 
FWIR, multiple 480VAC 400A feeds (192kW)
Split into the three phases
208VAC 40A feeds each of the 12 chargers in the cabinet
12 chargers are ganged together for 120kWh of charging.
Chargers produce lots of DC, which is bypassed through the car's onboard chargers to the battery.

Oh, and it's never been a "typical pole transformer". It's going to be a pad mounted beast of a transformer.
 
Last edited:
So does that mean you would only see 120 kW charge if both your bank is low enough and your the only one using one of those 12 bays?

Pretty much. It actually isn't that you have to be the only one charging - you just have to be the only one (or at least the first one) using a given set of charger modules, which are shared between two stalls.

If there are 12 bays, six of them can have 120 kW at any given time if the cars are in the right 6 slots and the state of charge and battery temperature permits it.
Walter
 
Each 120kWh Supercharger cab should have an A and a B station. The B station is a slave to A. If there is a greater need in the A station, it gets the power from B. If two dead cars show up and plug into the same cabinet's A and B station, the A car will get full power until it starts to throttle. Once it throttles, the "leftover" power goes to the B side.
 
Each 120kWh Supercharger cab should have an A and a B station. The B station is a slave to A. If there is a greater need in the A station, it gets the power from B. If two dead cars show up and plug into the same cabinet's A and B station, the A car will get full power until it starts to throttle. Once it throttles, the "leftover" power goes to the B side.

I was under the impression that it was pure FIFO - as in, if a car plugs into B when there's no car in A, it gets the 120 kW - and if a car later plugs into A while the B car is still charging, the B car continues to have priority and full power, while the new A car waits. Is this not the case?
Walter
 
Pretty much. It actually isn't that you have to be the only one charging - you just have to be the only one (or at least the first one) using a given set of charger modules, which are shared between two stalls.

If there are 12 bays, six of them can have 120 kW at any given time if the cars are in the right 6 slots and the state of charge and battery temperature permits it.
Walter

This gets me back to the original question, and that is how does existing infrastructure in a typical parking lot support this amount of power draw without some kind of buffer like 500 kWhr of batteries at the station.

I did some research and answered my own question. Tesla uses (12) of their 10 kW in a ganged network, so the draw from the mains is always a manageable 120 kW. I just couldn't see typical power in restaurant parking lots being able to go much higher than 120 kW, like if on a 12 bay station, 6 could pull 120 kW, which is way more than the mains could provide. So it is 120 kW only if your the only one charging, no matter how many stations are there unless special mains were provided.

How Tesla Superchargers Outsmart the Electric Car Industry | PluginCars.com
 
Last edited:
This gets me back to the original question, and that is how does existing infrastructure in a typical parking lot support this amount of power draw without some kind of buffer like 500 kWhr of batteries at the station.

The existing infrastructure in the typical parking lot doesn't support that kind of power. Tesla works with the lot owners and utility companies and has their own dedicated transformers installed from the utility mains. There are lots of construction photos scattered around the forum.
Walter
 
I was under the impression that it was pure FIFO - as in, if a car plugs into B when there's no car in A, it gets the 120 kW - and if a car later plugs into A while the B car is still charging, the B car continues to have priority and full power, while the new A car waits. Is this not the case?
Walter

It isn't FIFO like some people believe. I followed a Supercharger tech from Colorado to Kansas and chatted with him along the way. B is indeed a slave to the A side and it will give up most of its power if the need is on the A side. If you're plugged into B and someone plugs their car into A and it needs more than is leftover from your car charging, it will take it. The only way the B side would get almost no power is if someone pulled into the A slot with an almost dead battery ("Charge Now")
 
It isn't FIFO like some people believe. I followed a Supercharger tech from Colorado to Kansas and chatted with him along the way. B is indeed a slave to the A side and it will give up most of its power if the need is on the A side. If you're plugged into B and someone plugs their car into A and it needs more than is leftover from your car charging, it will take it. The only way the B side would get almost no power is if someone pulled into the A slot with an almost dead battery ("Charge Now")

Interesting. This is the first time I've seen that described.
 
The big transformers, and other charging equipment is usually in a little "pen" off to the side of the actual supercharger connecting posts.

Check out the little fenced rooms in these pictures:
36.jpg

tesla-100th-supercharger-hamiltion-NJ-10.jpg


I think they could have a "trickle charge" (of sorts) to a battery bank for locations that don't have sufficient primary power, but I don't think they have done much of that yet (if at all.)
Some locations do have battery banks but I think that is more about grid balancing (to avoid peak demand charges, and capture cheaper power at night when rates are lower.)

Many places don't have sufficient extra power available for this sort of thing. They have to research and find only suitable locations. I suppose if they wanted a location badly enough, they could work with the power company to upgrade the main power distribution coming to the site. (But that could get very expensive and time consuming.)
 
Are the A and B sides marked in some way? Sounds like you want to select the A side whenever possible to avoid reduced charge rate when someone else arrives.

Yes. They are clearly marked 1A, 1B. Sometimes the A and B are next to each other and sometimes all the A and all the B pedestals are grouped together.
 
The big transformers, and other charging equipment is usually in a little "pen" off to the side of the actual supercharger connecting posts.

Check out the little fenced rooms in these pictures:
36.jpg

tesla-100th-supercharger-hamiltion-NJ-10.jpg


I think they could have a "trickle charge" (of sorts) to a battery bank for locations that don't have sufficient primary power, but I don't think they have done much of that yet (if at all.)
Some locations do have battery banks but I think that is more about grid balancing (to avoid peak demand charges, and capture cheaper power at night when rates are lower.)

Many places don't have sufficient extra power available for this sort of thing. They have to research and find only suitable locations. I suppose if they wanted a location badly enough, they could work with the power company to upgrade the main power distribution coming to the site. (But that could get very expensive and time consuming.)

Thank you for taking the time to post, your text and pictures answers a lot of my questions.
 
In the background of the second picture (with Tesla logos painted on the tarmac) you can see a huge green pad-mounted utility transformer. For a site with 6-8 stalls, it would typically be a dedicated 500kVA transformer outputting 277Y480V power. There is some disagreement in this community about whether Tesla uses the Euro-style 3-phase on-board chargers, or they use the 40A single phase chargers, but allow them to go up to 277VAC at full current. In the car, the charger will decrease the current to limit the power to 10kW when you go over 250VAC.
 
Some more Supercharge stations with supporting equipment cabinets showing:
null-5.jpg

tesla-supercharging-station.jpg


I think not all locations are the same. There are different vintages/versions of supercharging, and different equipment requirements for some sites.
 
It isn't FIFO like some people believe. I followed a Supercharger tech from Colorado to Kansas and chatted with him along the way. B is indeed a slave to the A side and it will give up most of its power if the need is on the A side. If you're plugged into B and someone plugs their car into A and it needs more than is leftover from your car charging, it will take it. The only way the B side would get almost no power is if someone pulled into the A slot with an almost dead battery ("Charge Now")

I have never seen a charging session of mine throttled by another S plugging into the other pedestal of a paired Supercharger. That doesn't rule out the possibility that I've just been lucky and always have been plugged into the A side when someone else plugs into the B side; but I've never heard anyone else claim that A is always the Master and B is always the Slave. And aren't there some SpCs that dispense with the A/B markings entirely?

@Chris TX: FWIW the people who work for Tesla have not always proven to be a reliable source of information...and that's an understatement. :wink:

As others have noted, the sharing of charging power is done at 10kW granularity: each 10kW charger in an SpC cabinet is dedicated to one or the other of its two pedestals at any given time.