Newb Asks: Why Do We Need A Proximity Pilot Signal For Our EV Conversions?

[Gregski]

There will come a time when your EV Conversion reaches the point where you want to pull up to a public charging station and plug your rig in, if for nothing else than for the sheer shock value, am I right? Well in order to interface with the EVSE (a docking station for cars) there are a couple of handshakes that take place. One of them is a Proximity Pilot per the Wiki (also known as plug present), this tell the car it is plugged in to a charging station. Well why do we need that? My 1st Gen Chevy Volt charger works great without no Proximity Pilot signal already simply plugged in to a wall socket, so nothing stops it from charging without getting any Proximity Pilot signal. I get there is a safety element as this signal prevents the OEM car from starting so knuckleheads don't end up driving away with their cars still plugged in, but safety aside, why do we need it for functionality where Volt charger has no built in intelligence to do anything with that signal or does it?

Let's keep this discussion on point and not bring up the other pin aka the Control Pilot, that one I think we need.


one of these wires is for the Proximity Pilot the other is for the Control Pilot, I forget which is which.

IMG_9167.JPG (40.94 KiB) Viewed 4287 times

IMG_9083.JPG (27.94 KiB) Viewed 4287 times

[Bigpie]

The Prox pin doesn't connect though the cable, at least not here in the UK where public chargers are not tethered. The EVSE side connector has a resistor between PP and GND to denote the MAX current the cable and connectors can carry. Our public chargers are Type 2.

On the Car side, I use the PP to wake up the charger etc.

[uhi22]

Exactly. I formulate it in other words: Each plug has a resistor between PP and PE. The entity where the plug is plugged-in (vehicle or wallbox) measures this resistance value. The resistance value defines the maximum current which the cable can carry.
In practice, this means: If you have a 32A wallbox and a car which is capable of pulling 32A, and a thin cable which can only carry 20A, the PP resistors will tell the wallbox and the car, that 20A is the limit.
The table with resistances is here: https://www.goingelectric.de/wiki/Typ2- ... codierung/

[Gregski]

Tethered vs Untethered Chargers

The Prox pin doesn't connect though the cable, at least not here in the UK where public chargers are not tethered. The EVSE side connector has a resistor between PP and GND to denote the MAX current the cable and connectors can carry. Our public chargers are Type 2.

On the Car side, I use the PP to wake up the charger etc.

thank you for your answer, let's start off by understanding the difference between tethered and untethered chargers, I mention this because here in the States all the public charging stations I have seen look like gasoline fuel pumps with the shower head like cords attached to them, aka tethered, so the concept of untethered is [ahem] foreign to us, I wonder how they do in Canada, or Mexico?

[Gregski]

Exactly. I formulate it in other words: Each plug has a resistor between PP and PE. The entity where the plug is plugged-in (vehicle or wallbox) measures this resistance value. The resistance value defines the maximum current which the cable can carry.
In practice, this means: If you have a 32A wallbox and a car which is capable of pulling 32A, and a thin cable which can only carry 20A, the PP resistors will tell the wallbox and the car, that 20A is the limit.
The table with resistances is here: https://www.goingelectric.de/wiki/Typ2- ... codierung/

thank you for this explanation, please bear with me as I dumb it up so I can understand it.

"... Each plug has a resistor between PP and PE. " PE stands for Protective Earth aka ground

[Bigpie]

Yes, PE is ground or Protective Earth. Untethered would be nice here, but older cars use type 1 where as modern EVs are all type 2 here and in Europe.


I did a video when I made my cable for untethered EVSEs that I hope is clear to understand.

[Gregski]

Lessons Learned

So it appears that the Proximity Pilot signal was meant for untethered charging stations, meaning ones with no charge cords hard wired to them. All the charge stations I have seen in the States have the cables attached so no wonder this concept was a bit foreign to me.

PP (Proximity Pilot) – For Detachable Cable Assemblies
When a tethered cable is attached, the maximum current advertised by the EVSE should naturally not exceed the maximum capability of the charging cable. In this case, the maximum current is hardcoded, and the PP line is normally not connected back to the EVSE electronics.

However, when an EVSE accepts detachable cables, it must first determine the maximum current carrying capacity of the cable. This is done via a resistor mounted in the plug between PP and PE of the detachable cable.

[arber333]

Lessons Learned

So it appears that the Proximity Pilot signal was meant for untethered charging stations, meaning ones with no charge cords hard wired to them. All the charge stations I have seen in the States have the cables attached so no wonder this concept was a bit foreign to me.

PP (Proximity Pilot) – For Detachable Cable Assemblies
When a tethered cable is attached, the maximum current advertised by the EVSE should naturally not exceed the maximum capability of the charging cable. In this case, the maximum current is hardcoded, and the PP line is normally not connected back to the EVSE electronics.

However, when an EVSE accepts detachable cables, it must first determine the maximum current carrying capacity of the cable. This is done via a resistor mounted in the plug between PP and PE of the detachable cable.

Well in EU version PP pin is intentionally designed in such a way so it is the LAST pin inserted into the EVSE socket which will trigger start of the charging process ONLY when every other pin is firmly inserted.
Inversly PP is also the pin FIRST unplugged when removing the charging handle from the EVSE socket. This provides enough time for EVSE relays to disconnect power so it will stop charging safely.

In the USA you use J1772 standard which has a resistor divider built in. You need to press the button and insert the plug into the car socket. This then will signal the car to innitiate charging. See the divider in "EVSE connector" side of the schematic.
If you press the button (unplug 330R resistance) charging will stop. However there is a step built into the J1772 vehicle socket which will push on the latch when inserting the plug - helping you activate EVSE.

[Gregski]

Well this just keeps getting more and more interesting. I went out and bought the J1772 Active Vehicle Control Module AVC2 - For Public Charge Stations from EV West

EV West j1772-active-vehicle-control.jpg (6.9 KiB) Viewed 4089 times

and the first thing they tell you to do is to "Measure the resistance from the PROX pin to the GND pin on the inlet connector before it is connected. If it measures 2740 ohms you have the resistor already ... "

Wait what? Are you telling me the 1st Gen Chevy Volt charge port already has a built in Proximity signal resistor?

[Gregski]

a car plugging in simulation video using a pretty cool Wide-Range Precision Resistance Substituter

[arber333]

.....
Wait what? Are you telling me the 1st Gen Chevy Volt charge port already has a built in Proximity signal resistor?
......

It is inside the socket moulding. I use one J1772 socket in my Mazda and when i wanted to use PP signal in EU style control i couldnt use the plug button to stop the charge. Finally i had to add one pullup resistor which was just high enough to keep the signal over 0.8V detection threshold when i would connect the plug and use the button.