Telsa on Board Diagnostics OBD-II

The Lotus had a LCD screen with BMS info. There was a lot of info on cell level about temperture and voltage level. The Tesla Model S doesn’t inform the driver with any information about the battery other than de SOC (state of charge). To get to this information you have to access the CAN-bus and read the CAN messages. To do so you need to find the diagnostic connector which is behind the shelf just beneath the main screen.

Telsa diagnostic connector

Telsa diagnostic connector

Tesla uses a proprietary connector instead of the standard OBD-II connector. Most diagnostic interfaces come with the OBD-II connector so an adapter cable is needed.

Model S Adapter cable

Model S Adapter cable

To see the CAN-bus info you need software that is capable of translating the Tesla CAN messages. You can use Scan My Tesla for Android or TM-Spy for Apple. Since I have an Android Phone I went for Scan My Tesla and bought a OBDLink MX ABD-II adapter.


OBDLink MX with cable



The Lotus could charge on a standard CEE plug with max 32A on one fase. The Tesla has a duo charger which can handle 3x32A (3x32Ax230V equals 22KW) but it needs a Mennekes type plug with CP and PP contact. I could have gone the easy way and purchase a Tesla Wall Connector for nothing less than €530,- or any other 22KW charger, but I would like to know if I could build one myself for less. sells a EVSE kit for €50,- which is basically a board based on PIC micro controller which is able to generate 1KHz PWM Signal to detect the vehicle and control the relay.

parts needed:

  • GWL/Power EVSE Kit v1.1 for EV charging station/cable (Wallbox) – kit only
  • Relay capable of switching 230V/32A
  • mennekes type 2 female plug
  • 220 Ohm resistor
  • 5X6mm2 with wire for CP signal
  • Housing
EVSE schematic

EVSE schematic

Installed end result with a temporary charge cable and CP wire ( I didn’t have the right 5G6 + 2×0,75mm charge cable)


Plugged in to the Model S

Model S chargeport

Charging at 22KW

3x32A charging

3x32A charging