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OpenEVSE DIY Tethered 3-phase

When charging an EV the thee-phases will be balanced i.e the on-board charger will draw the same current from each phase, therefore the measurement will be accurate. Although if billing grade energy reading is required It would be best to also install a 3-phase utility meter inline.

Thank you!

    I'm working on a new controller board based on openEvse.

    The board will only support an alternating current relay and will be suitable for mode 3 installations.

    Do you think that three current sensor circuit one for each phases  will be a good solution?

    I need an billing grade energy reading.

Yes, if you have available inputs on your controller board I would recomend adding the option for 3 x CT inputs. Also a AC voltage monitoring circuit would be a good addition to monitor the AC voltage.

True, maybe i can use the relay sense input line.

To connect a type 2 Menekes 3 phase tethered to OpenEVSE, must I install any resistance in any place (in he plug).
If yes can you put a connexion scheme?

No cable modifications should be made. Only the EmonEVSE supports three-phase, the EmonEVSE will automatically detect the current rating of the attached non-tethered cable and will set the max current accordingly. See:

How the system know the maximum capacity of the cable?

Has the cable any electronics to inform about that?

I’m doing an OpenEVSE tethered 3 phase following this

Jordi Llovera

Yes, all T2 non-tethered cables have a resistor between PP and GND which inform the EVSE of the rating of the cable. See my link posted above for more details.

This resistor is located in the EVSE end of the cable and is only used in non-tethered EVSE’s since in the case of a tethered EVSE the cable connected is always the same therefore the max current rating can just be set once at installation. In the case of non-tethered units like our EmonEVSE any cable of any rating could be connected at anytime. The PP wire is not used for non-tethered units.

Hi Glynn

I installed again the EVSE you sent and it doesn’t work

Please I need your help !!!

I have an:


3 phase 400V

Tethered Menekes

Firmware actualized to 3 phases: openevse-3ph.hex

I’ve disabled GFCI because I’ve a 30mA differential

I connect to the car and it doesn’t charge.

The display says “Connected” but it doesn’t work.

The 3 phase relay doesn’t connect because there is no tension between in coil.

I tried with a BMW i3 and Renault ZOE with the same result.

Can you tell me if my DIAGRAM is correct?

I verified that the ground cable is really connected to my house’s ground with 0 Ohms of resistance

Please can you answer all this questions?

1.- The violet cables as a Coil test are connected between L1 and Neutral. (your diagram is between L1 and L2, then 400V, wich one is correct?

2.- I connected PP and CP. Is this correct?

3.- Why it doesn’t charge?

4.- can OPENEVSE charge with tethered cable ?

5.- must I put any resistor between PP and ground to say to EVSE my car is plugged as an un-tethered (I don’t have an EMON EVSE but an OPEN EVSE)?

6.- Is my firmware, useful for that?

Thanks for your answer

Kind regards

Oh dear, there must be some issue with your installation. I tested the unit extensively

These pins are stuck contact detection and should go to the output of the relay L1 and neutral. which diagram are you referring to.

No need to connect PP on a tethered system

Good question, it was working when I tested it! Please share some more photos of your setup so I can better understand how you have connected it.

The standard OpenEVSE kit which you have is for a Tethered Cable. Using a non-thered cable requires different firmware. The OpenEVSE kit does not have a non-tethered type two socket. I would recommend using an EmonEVSE three-phase if you want non-tethered: EmonEVSE WiFi Connected EV Charging Station (Type-2) - Shop | OpenEnergyMonitor

All untethered cables have a resistor ready built in. If your running EmonEVSE firmware then this resistor is require to turn on. Are you trying to build an un-tethered system? Please share photos so I can understand.

What firmware are you running?

The device is still not charging the vehicle, the main board is not supplying the required voltage to the contractor coil.

Please find below a summary of the current situation of the issue:

I bought an OpenEVSE charger, to install tethered and triphasic.

I changed the original monophase contactor by Schneider 3 phase + N and 240V coil.

My firmware is version 5.1.0.EU openevse-3ph.hex from may 2019

I disabled GFI test because I’ve an RCD.

I’m using this EV car plug IEC 62196-2 ZWET EVSE 32A IEC 62196 2 EVSE Cable Female Plug 3 phase For Electric Vehicle Charging car end plug iec 62196 2|Chargers & Service Equipment| - AliExpress

I connected CP and PP wires from the EV plug to the main board.

There is no resistor installed between Ground and PP.

The Wifi connection works OK (version 2.7.7.)

I used the following connexion diagram Can OpenEVSE provide 3 Phase power to the Electric Vehicle? : Support

When I connect the charger to the grid the display says “READY”

When I connect the car (BMW i3) it says “CONNECTED L2:16A” but it doesn’t charge.

I checked all these points without any result:

  • No AC power to AC_Input
  • LCD 4-pin connector is reversed
  • Short on output will put power supply into protection mode
  • Fuses next to AC_Input on the board blown (labeled “bel”)
  • Power Supply module has failed
  • Supply voltage measured at AC INPUT is 240V (normal).

  • I have tried to invert the connection between the AC INPUT 1 and the AC INPUT 2, but the charger is still not charging.

  • I tested the ground connexion in all the points on the diagram to check continuity (all OK).

  • I checked the supply voltage for the display = 5 V.

  • I measured the voltage between lines and are from 398 V to 405 V, and between Lines and neutral are from 229 V to 231 V (normal).

  • I checked the 2 fuses labelled “bel” in the main board and they are OK.

  • The contactor does not click and the coil doesn’t receive any Voltage from the charger. If I put 240V directly to the coil, the contactor clicks correctly.

  • I checked output tension for the 240 V coil and 5 V coil. All of them are at 0 V.

I checked the CP voltage in differents status and the results are:

  • CP "not connected" = 11.58 V
  • CP "EV Connected" = -4.56V
  • CP "Sleeping" / "Pause" and "Connected physically" = 8.95 V

Do you have any idea why the main board is not sending the required voltage to the coil?

Please, may you advise me on what else I can check? I don’t understand why the device was working when you tested it yourself and I don’t manage to make it work at home. I am following every step of the guide but it never charged my vehicle, even if it every part seems to be working. I even tried it with a Renault Zoe and got the same negative result.

I have the kit since one year at home and I really would like to make it work but I need your support.

Thank you very much for coming back to me,

Kind regards,


Sorry to hear your still having trouble.

The PP wire is not required for tethered installation. Try disconnecting it.

If your still having issues, I recommend getting a EV simulator board to allow you to test each state individually:

The controller was definitely working when it was shipped.

Hy Glyn
I tried all that yet.

I disconnected PP wire and nothing happen

I tried too with a simulator with 882 ohms and diode. the disply says “error ventilation required” in red

can be the firmware?

kind regards


It would be a good idea to test with the standard OpenEVSE firmware non three-phase:

Hi Glyn
Finally I found the problem.

I need a resistor between Ground and PP wire, car side.
PP is not connected to the main board.
In my case the cable is 6mm2 = 32 A and my type 2 plug is also 32A.
The resistor to work with this intensity must be 220 Ohms.
I put a 240 Ohms because I had it at home.
It charge !!! :slight_smile:

Now the problem is the firmware energy calculation in kWh.
Look at the print screen. The charging current was between 16 and 17 Amps all the time in 3 phase. Voltage was around 400V. Thats about 11kW for 1h41 min. The energy must be around 18,7 kWh and no 2,62 kWh as represented.

Can you arrange that calculation please?
Kind regards


Ah, that’s good to hear. Most EV connectors come with the resistor pre-installed. This is the first time I’ve heard of a connector being supplied without a resistor. Did you make up your own cable? For anyone else following this thread here is some more info on resistors in charging cables:

This only applies to Type-2 cables, Type-1 cables don’t have a resistor at the car end, at least not connected as standard between PP and GND. A resistor is connected via the switch on the connector which signals the EV to stop drawing current when the switch is pressed :


Enabling #define THREEPHASE in open_evse.h should enable three-phase energy calculation. This should be enabled as standard if you are running three-phase FW. Could you show me a screenshot of the openevse UI showing the controller FW? It should end in .3P if it is indeed running 3ph firmware.

Hi Glyn
Yes I did my own cable and installed a type 2 plug.
how I do that?:
Enabling #define THREEPHASE in open_evse.h should enable three-phase energy calculation. This should be enabled as standard if you are running three-phase FW. Could you show me a screenshot of the openevse UI showing the controller FW? It should end in .3P if it is indeed running 3ph firmware.

the FW you send me to install is openevse-3ph.hex in may 2019

Apologies, I must have made a mistake. I’ve just recompiled a special OpenEVSE FW with THREEPHASE enabled. The firmware version is 5.1.0.EU.3P. See attached:

firmware.hex (85.8 KB)

Sorry Glyn
I just uploaded the new firmware and the calculations are again for monophasic, not triphasic (see pictures attached).
Power 3p = 400V x AMPS x SQRT(3)