My Own Supercharger??

[lolachampcar]

OEMs are getting smarter about protecting their proprietary hardware from reverse engineering. Sure you can sniff the SC to car communication in an effort to reverse the process and this is perfectly legal. However, I would not be surprised if Tesla is using something like a BMWish style RSA encrypted message query to start any communication. Any tester connected to the newer BMWs will ask the car for a message. This message (RSA encrypted) is then decrypted by the tester and returned to the car for authentication before a communication session can begin.

RSA is no big deal (apart from dealing with larger numbers in a micro controller which is a PITA) but it is a big deal to posses private keys without the owner's permission. This is the part that gets the reverse engineers sued unless they can prove that they factored the keys (instead of getting them out the back door from the owners).

This communications challenge is but one way OEMs are shutting hackers down. I would think Tesla would have looked into this given the enormous warranty liability wrapped up in all those battery packs. I know I would not want anyone else charging my packs if I were writing the check to fix things that go awry.

 

[FlasherZ]

Gotta' remember that a Supercharger doesn't use the single or twin on-board units at all. It a direct feed of up to 250 amps to the pack, at whatever pack voltage is when initially connected (345++).

The $2000 premium for the 60kWh option to accomodate a Supercharger is the high current bus bars/cables and necessary switching circuitry.

So that "refrigerator sized box" is fed 480 or 277 V from the secondary of that monster 500 kVA xfmr, depending on what it's designed for. I'm guessing 277, since that not too big of a departure from a 240 V rms residential line voltage level. Three or four of the 12 would be wired on each L-N, to all are evenly balanced.

This is understood - contactors are present to switch the L1 and L2 pins on the charger directly to the battery.

The 277V to the SuperCharger cabinet is at odds with what Tesla has published. Tesla has said that the Supercharger is built upon the same chargers used in the car -- they're just mounted externally in a cabinet and create a high-current DC power buss.

Tesla's specs say input voltage is 80-265V for these chargers, and 277V L-N would be out of spec for them. This is reason for my assumption that they're not fed by a 480V 3-phase wye, but rather a 240V delta configuration. Primary voltage is likely to be the standard 14.4 kV, and by using a 240V L-L delta configuration, you can get in-spec voltage for the chargers. Since the load is already inherently balanced, you don't have to worry about issues there.

As consumers, we don't have to worry about this but I'm just curious.

 

[pilotSteve]

For an IT guy (I think that what you once posted) you sure know lots about high power/high voltage engineering Love your insights and posts!

 

[FlasherZ]

For an IT guy (I think that what you once posted) you sure know lots about high power/high voltage engineering Love your insights and posts!

Thanks

My father was always the electrician of the family, and I've always had a leaning toward the EE/hardware side of computer engineering.

 

[mitch672]

This is understood - contactors are present to switch the L1 and L2 pins on the charger directly to the battery.

The 277V to the SuperCharger cabinet is at odds with what Tesla has published. Tesla has said that the Supercharger is built upon the same chargers used in the car -- they're just mounted externally in a cabinet and create a high-current DC power buss.

Tesla's specs say input voltage is 80-265V for these chargers, and 277V L-N would be out of spec for them. This is reason for my assumption that they're not fed by a 480V 3-phase wye, but rather a 240V delta configuration. Primary voltage is likely to be the standard 14.4 kV, and by using a 240V L-L delta configuration, you can get in-spec voltage for the chargers. Since the load is already inherently balanced, you don't have to worry about issues there.

As consumers, we don't have to worry about this but I'm just curious.

The one CA SuperCharger site than showed the 480V 500KVA transformer also had an "extra" Eaton box, that box likely contained transformers or a buck-boost setup to get the 277 down to specs (240-250V ideally), for each phase. It could have been that for the amount of power required at the site, the local utility only had a 480V transformer availble at the time, or it might be their policy to only delivery 500KVA service on 480V. Most of the other pictures seen at SuperCharger sites don't have the "extra" eaton box, they are likely just being fed 120-208 service directly.

So yes, you are correct, the power needs to be the same specifications as the car, since they are just using 12 of the same chargers in the SC

 

[FlasherZ]

The one CA SuperCharger site than showed the 480V 500KVA transformer also had an "extra" Eaton box, that box likely contained transformers or a buck-boost setup to get the 277 down to specs (240-250V ideally), for each phase. It could have been that for the amount of power required at the site, the local utility only had a 480V transformer availble at the time, or it might be their policy to only delivery 500KVA service on 480V. Most of the other pictures seen at SuperCharger sites don't have the "extra" eaton box, they are likely just being fed 120-208 service directly.

They're going to want the most efficient distribution. It's unlikely to be 120V wye (208V L-L) for that application, and a bucking autotransformer is going to be wasteful too.

Sitting here, it makes more sense that it may indeed be a 480V 3-phase from the utility. I looked at it from the perspective of a single SC, but at a site where you need multiple bays each doing this, it makes sense. A cabinet is fed 480V and has a simple step-down to derive 240V.

Maybe in time we'll learn the typical setup.

 

[gaswalla]

Oops, wrong thread

 

[FlasherZ]

'tis ok, forced me to read above and restate my position. Quite a long time ago, I noted that I didn't expect 277V to the cabinet, I changed my opinion shortly after this post and from other evidence that supports 277V L-N being used at most Supercharger cabinets from 480V L-L 3-phase.

 

[Cottonwood]

'tis ok, forced me to read above and restate my position. Quite a long time ago, I noted that I didn't expect 277V to the cabinet, I changed my opinion shortly after this post and from other evidence that supports 277V L-N being used at most Supercharger cabinets from 480V L-L 3-phase.

There was a post recently of the label of a single charging module. They are rated for up to 277 Volts in. Also, in Squamish, they are using an autotransformer/buck-transformer to convert the 600/346 Canadian Voltages to 480/277 for the Supercharger Cabinets.

Yes, Tesla appears to be driving each of the 12 individual charging modules in the Supercharger Cabinet with 277 Volts L-N. It would make sense that they connect 4 modules to each phase. Interestingly, 12x40Ampsx277Volts = 132.96 kW; that is pretty close and could be rounded up to the 135 kW power that Tesla is claiming on the latest Superchargers.

 

[TonyWilliams]

Interestingly, 12x40Ampsx277Volts = 132.96 kW; that is pretty close and could be rounded up to the 135 kW power that Tesla is claiming on the latest Superchargers.

I know I've mentioned this before in the forum, but the firmware in the car limits the charger to 10kW, whereby 40 amps is held to 250 volts, then ramped down to 36 amps at 277 volts (we actually tested it).

So, the 120kW Superchargers likely retain the 36 amp limitation per charger module at 277 volts, and the 135kW likely are at 40 amps at 277 volts.

 

[wk057]

I know I've mentioned this before in the forum, but the firmware in the car limits the charger to 10kW, whereby 40 amps is held to 250 volts, then ramped down to 36 amps at 277 volts (we actually tested it).

So, the 120kW Superchargers likely retain the 36 amp limitation per charger module at 277 volts, and the 135kW likely are at 40 amps at 277 volts.

You fed your car 277 volts AC?! Not sure I'd have tried that one.

 

[TonyWilliams]

You fed your car 277 volts AC?! Not sure I'd have tried that one.

Why? The charger is placarded as 277 volt capable.

You probably don't cut apart your Tesla car parts like I do either?

Tesla Model S UMC cut open and modified to J1772 - Page 13