01
Background
As an Electrical Engineer and an EV owner, curiosity got the best of me and I took a deep dive into the J1772 Standard. I wanted to learn about the safety devices incorporated into the standard, how charge rates were dictated, and other nuances. With this information, I also wanted to develop a product to help with specific EV charging scenarios which I'll get into below.
02
Photos
Here is the pinout for SAE J1772. It consists of a L1 (AC Line 1), L2/N (AC Line 2 / Neutral), PE (GND), PP (Proximity Pilot / Plug Present), CP (Control Pilot / 1 kHz Square Wave).
Here is the pinout for SAE J1772. It consists of a L1 (AC Line 1), L2/N (AC Line 2 / Neutral), PE (GND), PP (Proximity Pilot / Plug Present), CP (Control Pilot / 1 kHz Square Wave).
This is the Signaling Schematic. This shows where signals are generated in the EV handshaking procedure. We'll be signal tapping the EVSE Connector via an adapter.
This is the Signaling Schematic. This shows where signals are generated in the EV handshaking procedure. We'll be signal tapping the EVSE Connector via an adapter.
This is a TeslaTap, a commercial off the shelf product. It's a passive adapter, which just does pin remapping. I'll be disassembling the J1772 end to gain access to the PP/CP signals.
This is a TeslaTap, a commercial off the shelf product. It's a passive adapter, which just does pin remapping. I'll be disassembling the J1772 end to gain access to the PP/CP signals.
Here you can see the two resistors labeled R6/R7 in the EVSE Connector on the block diagram. This is for the Proximity Pilot. When the mechanical latch is pressed, the 330 Ohm R7 is added causing a voltage shift commanding the vehicle to shut off prior to disconnecting.
Here you can see the two resistors labeled R6/R7 in the EVSE Connector on the block diagram. This is for the Proximity Pilot. When the mechanical latch is pressed, the 330 Ohm R7 is added causing a voltage shift commanding the vehicle to shut off prior to disconnecting.
I used some 3-way Wago 221 Series Lever Nuts to maintain the connection while passing a wire outside of the enclosure. This will allow me to monitor the PP/CP signals.
I used some 3-way Wago 221 Series Lever Nuts to maintain the connection while passing a wire outside of the enclosure. This will allow me to monitor the PP/CP signals.
Here you can see the 1kHz Square Wave being transmitted on the CP. The vehicle controller looks for this 1 kHz CP before initiating charging.
Here you can see the 1kHz Square Wave being transmitted on the CP. The vehicle controller looks for this 1 kHz CP before initiating charging.
Here you can see our 1 kHz CP drop from high to low. We have significant activity happening on both the highside and low side when charging initiates.
Here you can see our 1 kHz CP drop from high to low. We have significant activity happening on both the highside and low side when charging initiates.
Once we zoom in we can see what looks like a couple of distinct steps at various voltage levels, approximately 20 mV per divission.
Once we zoom in we can see what looks like a couple of distinct steps at various voltage levels, approximately 20 mV per divission.
01
Product
With this understanding, I was able to build a product for a friend which exploits the PP and CP behavior to simulate unplugging and replugging a car in. I go into further explanation below if you're interested: