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Small question for the Teslarati on this forum: how does a supercharger know that a Model S is allowed to use the charging facilities? Does the car send some instructions over the cable when connected, or do you have to wave an RFID card?
 

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Driving yet another EV!
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Small question for the Teslarati on this forum: how does a supercharger know that a Model S is allowed to use the charging facilities? Does the car send some instructions over the cable when connected, or do you have to wave an RFID card?
The car sends its VIN details to the charger. All EVs and chargers should work like this!
 

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22,000,000 cars in the UK, VIN numbers are 17 digits. Reg no 8 digits. To store all that in the rapid posts memory + say a 128 bit (16 byte) public encryption key would take :
17 + 8 + 16 = 41 bytes per car.

x 22Million = 902,000,000 bytes or 902MB (not MiB).

That's about £20. To allow you to authenticate without a network signal, and bill in arrears (a bit like an EPOS system then!)

All this RFID stuff is a nonsense created by OLEV wanting usage stats.
 

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22,000,000 cars in the UK, VIN numbers are 17 digits. Reg no 8 digits. To store all that in the rapid posts memory + say a 128 bit (16 byte) public encryption key would take :
17 + 8 + 16 = 41 bytes per car.

x 22Million = 902,000,000 bytes or 902MB (not MiB).

That's about £20. To allow you to authenticate without a network signal, and bill in arrears (a bit like an EPOS system then!)
Far more data than you need.

You don't need the reg, the VIN is enough. The VIN is base 36, so you can fit those into 6 bytes. Also the VIN is required by law to be publicly visible so you wouldn't need to encrypt them individually (though encrypting the whole data block is probably a sensible idea).

As for recognising if the VIN presented by the car is authorised to charge, then simply the existence on the list would be enough.

So you would only need the VINs in the list of EV's which is likely to be less than 1m for a while yet.

You'd fit it all that in < 6MB, and could push out the list on a scheduled basis.

All this RFID stuff is a nonsense created by OLEV wanting usage stats.
Completely agree.

I wish from the outset EVSE's had communicated over a two way digital channel (CANBUS seems ideal), just register your VIN on which ever service provider you wanted.
 

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The reg is only there for the CCTV to cross check so you don't get VIN fakers. Likewise the encryption key. But agreed. . By the time you need 22 million pre stored 200kW charging will be common place. Just really wanted to show it's not beyond the storage requirements of a typical computer to store the VIN every car in the country with a bit of additional data.
 

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No. Well maybe lol. I was trying to explain what i think would be a simple cashless way to pay for charging for all future charge stations Tesla or non Tesla. The car is your contactless ID ( well actually not contactless as it's over the wires).

Turn up plug in, go for a coffee no authentication required. Worst case scenario when comms are dow, the car still gets charged, the charger logs the transaction and sends the history back when comms return.
 

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No. Well maybe lol. I was trying to explain what i think would be a simple cashless way to pay for charging for all future charge stations Tesla or non Tesla. The car is your contactless ID ( well actually not contactless as it's over the wires).

Turn up plug in, go for a coffee no authentication required. Worst case scenario when comms are dow, the car still gets charged, the charger logs the transaction and sends the history back when comms return.
That would be perfect.

To fix the theft of electricity issue you'd need some sort of two part noonce exchange, but I think realistically the price point is such, providers would treat it in the same way shoplifting is figured into retail margins.

(or drive aways at petrol stations)
 

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In Tesla's case, although the car and charger do communicate possibly sending the vin to the charger, etc. I don't think this is part of activating the charging session - ie, the charger doesn't "know" internally or via the network if the car is SC enabled. The comms network is too unreliable.

However, I think the software onboard the car is the enforcing side of the conversation.

Ether that, or Tesla had the common sense to start the charging session and do the comms in the background, and only stop or cancel the charging if the car is not SC enabled. This way if the comms network fails, you potentially give away a few kWh of free electricity in return for having a considerably more reliable charge network.
 

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Indeed, Pod Point have now taken a similar approach. 15 minutes to get the authentication sorted while the car charges anyway. Which also means you can get an "emergency" charge - on a 7kW post/car 15 minutes gives you about 7 miles which is hopefully enough to get somewhere else.
 

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In Tesla's case, although the car and charger do communicate possibly sending the vin to the charger, etc. I don't think this is part of activating the charging session - ie, the charger doesn't "know" internally or via the network if the car is SC enabled. The comms network is too unreliable.

However, I think the software onboard the car is the enforcing side of the conversation.
This ^

When I upgraded my car for Supercharging it was via a firmware flash.
 

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No. Well maybe lol. I was trying to explain what i think would be a simple cashless way to pay for charging for all future charge stations Tesla or non Tesla. The car is your contactless ID ( well actually not contactless as it's over the wires).
Turn up plug in, go for a coffee no authentication required. Worst case scenario when comms are dow, the car still gets charged, the charger logs the transaction and sends the history back when comms return.
There is no need for the Supercharger to hold any data - it simply talks to the car & within the car's diagnostic data there is a parameter (that you cannot change) that says "Fast charge installed" & the reply True or False.
 

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There is no need for the Supercharger to hold any data - it simply talks to the car & within the car's diagnostic data there is a parameter (that you cannot change) that says "Fast charge installed" & the reply True or False.

That would seem more logical, are VINs unique worldwide? If not how could you use a supercharger in France for example?
 

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That would seem more logical, are VINs unique worldwide? If not how could you use a supercharger in France for example?
Yes VIN's are globally unique
Digits 1–3, World Manufacturer Identifier (WMI): 5YJ = Tesla
Digit 4, Line/Series: S = Model S
Digit 5, Body Type: A = 5 Door Hatchback LHD, B = RHD
Digit 6, Restraint System:
Digit 7, Charger Type (earlier VINs) or Battery Type (later VINs):
Digit 8, Motor/Drive Unit & Battery Type (earlier VINs) or Motor/Drive Unit (newer VINs):
Digit 9, Check Digit: Variable
Digit 10, Model Year:
Digit 11, Manufacture Location:
Digit 12, Production Series:
Digits 13–17, Production Sequence Number

- but again no authentication needed as it is the CAN protocol that turns the Supercharger on.
 
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