Tesla Pilot Signal Details

[suxxer]

Does anyone has details on the pilot signal (the extra pin inside the charge connector) Tesla is using? The pilot signal tells the car how much amps it can draw from a power source.

According to the specs the "Spare Connector" allows 15 Amps@120V in the US. My local Tesla dealer told me that they have 15amps@230V and 10amps@230V here in Europe. He told me they have "some modifications" on the cable in order to get 10 or 15 amps.

The "Universal Mobile Connector" on the other side seems to adjust the max. amps according to the plug connected. If you connect a NEMA 6-30 plug it's 30amps, connecting a NEMA 6-15 plug it's 15 amps.

Search yields some infos about the Pilot Signal Tesla uses. It seems to be a 12V 1kHZ square wave signal. It looks like the max current can be set by adjusting the duty cycle. According to the Avcon source a 50% duty cycle equals 30amps. (the ratio of the high period to the total period of a square wave is called the duty cycle. A true square wave has a 50% duty cycle - equal high and low periods.)

Can someone confirm that? Does this mean that even the "Spare Connector" has a built-in circuit who supplies the desired pilot signal? And/Or does the absence of a pilot signal default the max amps to 10amps?

 

[jaanton]

You want to read scott451's posts... The "Spare Connector" just ties the pilot pin to ground with the switch. (At least that's the USA version.)
The "Spare Connector" is really following the "Level 1" protocol while the square wave stuff is the "Level 2" protocol.

Charging the Roadster

 

[scott451]

Does anyone has details on the pilot signal (the extra pin inside the charge connector) Tesla is using? The pilot signal tells the car how much amps it can draw from a power source.

Tesla follows the J1772 spec. (Troy N and other folks at Tesla were/are actively involved in defining the spec)
IEC 309 is very simlar: http://www.park-charge.ch/documents/BOXSPECE.pdf

According to the specs the "Spare Connector" allows 15 Amps@120V in the US. My local Tesla dealer told me that they have 15amps@230V and 10amps@230V here in Europe.

For USA Roadsters, grounding the pilot pin (which is not part of J1772) allows the car to charge at 16A (80% of a 20A circuit) or 12A (80% of a 15A circuit). The NEC considers the EV as a "continuous load" hence the 80% derating. I've heard the 15A@230V and 10A@230V work the same way. No pilot, just a grounded pilot pin.

The "Universal Mobile Connector" on the other side seems to adjust the max. amps according to the plug connected. If you connect a NEMA 6-30 plug it's 30amps, connecting a NEMA 6-15 plug it's 15 amps.

I believe the UMC is a clone of the RFMC. The neutral pin is not used so Martin E. put a short/forward diode/reverse diode to ground in each of the adapters to indicate the available current.

Search yields some infos about the Pilot Signal Tesla uses. It seems to be a 12V 1kHZ square wave signal. It looks like the max current can be set by adjusting the duty cycle.

yes. It is a +12V/-12V square wave with a 1K ohm source resistance (as described in J1772)

According to the Avcon source a 50% duty cycle equals 30amps. (the ratio of the high period to the total period of a square wave is called the duty cycle. A true square wave has a 50% duty cycle - equal high and low periods.)

Correct. however Tesla modified the duty cycle equation above 48A to accommodate 70A charging. (this modification is now part of J1772-2010)

Can someone confirm that? Does this mean that even the "Spare Connector" has a built-in circuit who supplies the desired pilot signal? And/Or does the absence of a pilot signal default the max amps to 10amps?

I don't know what a "spare connector" is, but if it is like the 110V charging cable, then there is no pilot generator, the slide switch just shorts the pilot to ground.

 

[suxxer]

Thanks for the reply. According to the website Tesla calls the yellow charging cable "spare connector".

One thing still is unclear for me:

I've heard the 15A@230V and 10A@230V work the same way. No pilot, just a grounded pilot pin.

But how does the car know how much power it can take (10A or 16A)? You will have some problems if you have a 10A breaker and the car starts to suck 16amps. In my opinion just grounding the signal pin won't do the job. A grounded signal pin maybe just defaults the charge limit to 15amps@110V (US) / 16amps@230V (Europe). If Tesla tells me that they have two verisons (10A & 16A) of the yellow cable then the grounded signal pin wont do the job alone...


I took a look at Martins charger. The unit seems to work with the square wave signal on the output side. And it looks like it detects what plug you connect to the unit (on the input side) and sets the right charge limit. So here the limit is also detected by connecting the right plug.

 

[tomsax]

The RFMC looks for a diode between ground and what would normally be neutral on the twist-lock connector. If there is no diode, it assumes a 16A limit. If there's a diode one way, it signals 24A limit, if there's a diode pointed the other way, it signals a 40A limit.

I don't know how UMC does it, something similar I would guess.

If someone has the 10A/230V spare connector, it would be helpful to check for either a diode or resister between pilot and ground and post the results.

 

[marco2228]

Does anyone know what duty cycles Tesla used for the higher currents above 40 A?

 

[mitch672]

Does anyone know what duty cycles Tesla used for the higher currents above 40 A?

Yes, they follow J1772-2010, there's an explanation here: https://code.google.com/p/open-evse/wiki/J1772Basics

 

[tomsax]

Original Roadster HPC Duty Cycle Values

Does anyone know what duty cycles Tesla used for the higher currents above 40 A?

I tested an original Tesla Roadster HPC, one of the early ones before they started using the Clipper Creek units. It has a rotary dial to set the current limit, so I could test every setting. It agreed to within 0.1% of the J1772 spec for all values.

That's no surprise since Tesla (specifically, Martin Eberhard) proposed using Tesla's extension to the 2000 version of the J1772 pilot signal spec to accommodate charging up to 80A.

 

[TonyWilliams]

Does anyone has details on the pilot signal (the extra pin inside the charge connector) Tesla is using? The pilot signal tells the car how much amps it can draw from a power source.

IEC uses
1.5k pilot to ground 13a
680 - 20a
220 - 32a
100 - 63a