Interlock in Electric and Hybrid Vehicles

[@vwdasauto8125]

Important information..Thanks for sharing.Keep the rhythm going👌👌👌

[@johannaltmann6241]

Tolles Video! Vielen Dank dafür. Bitte achten Sie aber darauf, dass die als Widerstände gedachten Darstellungen R1 - R7 als Sicherungen (Schaltzeichen) dargestellt sind.

[@InsideEVTraining]

Danke für das Feedback und das Lob! Sie haben völlig Recht, da ist uns ein kleiner Fehler unterlaufen.

[@maheshpadmanabh6564]

Great explanation but can you tell where exactly you are measuring the voltage? Can you tell me the nodes?

[@InsideEVTraining]

Thanks :) Do you mean on a real vehicle? Unfortunately, this cannot be said across the board, this is normally done in the real vehicle by the diagnostic tester. It will tell you any fault code related to the interlock, but these faults will be recognized through the internal voltage measurement of the vehicles intelligence / on board measurement systems. Also the different voltage values should be displayed by the tester, IF the car manufacturer allows them to be displayed.

[@maheshpadmanabh6564]

@@InsideEVTraining no I meant in this video. The meter shows different voltages like 1.5V, 2.5V … 7V etc. so where is that voltage being actually measured? Across which resistors?

[@InsideEVTraining]

@@maheshpadmanabh6564 Over all resistors :) This is just a simple series circuit, where the volt meter is connected in parallel. So it is measuring the total resistance, which depends on the resistors are short-circuited or not.

[@maheshpadmanabh6564]

@@InsideEVTrainingif we are measuring across the points shown in the circuit then it should be always 12V. If it’s across only R1,R2,R3 and R4 then we should be seeing 6V instead of 1.5V. Is my understanding fundamentally flawed? Can you please help me out here :)

[@InsideEVTraining]

​@@maheshpadmanabh6564 You're on the right track overall, but let me clarify something important. We're utilizing a "constant current source" (the box in the left corner), which means the current remains unchanged at a steady 10 mA. This leads us to the equation U = R x I, where I is the constant current. Now, focusing on resistors R1 to R4 (we'll set aside R7 for the moment as it serves a self-diagnostic purpose), these represent the circuit's TOTAL RESISTANCE. However, this resistance can vary due to different plugs or connectors in the system. Take R4 as an example: when the HV service disconnect is connected, R4 effectively becomes non-existent, offering zero resistance (though technically, the cable itself has some resistance, but let's overlook that for simplicity). Consider what happens to the total resistance when you calculate for two parallel resistors and one has ZERO resistance. It significantly impacts the overall resistance measured in the circuit. Hope this helps clarify things!

[@Carli6543]

Great video! And so does R7 serve the same purpose as R1 or does it have a different job? Also, you have inverter, air compressor and service disconnect plug here - are there other components this travels through?

[@InsideEVTraining]

Thanks :) The interlock will basically be part of any high voltage component - so if you have a HV heating element, it will be probably part of the interlock. R7 is an internal resistance which helps to recognize a short circuit at the "outside". So basically the whole "cable harness" could be short circuit. Without R7 you weren't able to say if there is 0 voltage or a short circuit. But with R7 you habe a definied voltage drop, which tells the system there is a short circuit on the outside.

[@tinkukuty1232]

In this layout could you not short the pins on a connector, lets says using a safety clip or a needle, after unplugging it and trick the BMS into thinking that the HVIL is Okay?

[@InsideEVTraining]

This is absolutely possible! You can do this easily on a Prius 3 with the inverter cover. Of course just theoretically ;)

[@europechannel8410]

Great info thanks

[@InsideEVTraining]

Thank you :)

[@HelmutTschemernjak]

Great Video, thanks for explaining this details. In EV cars there is a PDU (power distribution unit) e.g. in the eVito. Do you know if this PDU is just distributing the HV voltage to the HV clients, or this there a current Fuse or electronic power measurement included in the PDU unit of Mercedes. Regards from Hannover Germany.

[@InsideEVTraining]

Hello Helmut, greetings from Cologne! Your question is a bit difficult to answer, as this is really individual for all car manufactures. I have heard about the Mercedes PDU, but can't remember in detail. But maybe this is a bit of help: "Eaton’s high-voltage power distribution units (PDUs) and power distribution elements (PDEs) deliver power to all critical loads within the electric vehicle (EV) system -- including traction and auxiliary loads -- while protecting electrical and electronic components and vehicle occupants with reliable circuit protection solutions. These PDUs, also known as junction or fuse boxes, are ideal solutions for battery electric vehicle (BEV) applications."

[@HelmutTschemernjak]

@@InsideEVTraining thanks for the input, I will look into it. I understand from Tesla EVs that they measure the power of the different HV clients (e.g. heat pump), in addition they have soft and hard fuses for this HV clients.

[@alisamehmohamed2020]

Hello, Thank you for this helpful information. I just have one confusing point 😅, I always thought the HVIL (High voltage Interlock) has 4 wires ( acting as bridge for each two wires) 2 for the 12 V/LV and the other 2 for the signa going the HV components through the BMS, then when we disconnect the HVIL the BMS will understand that there are missing signal then will disconnect the HV Contactors to shutdown the HV. So my question what's make the HV contactors open the missing of one of the resistance signal Or missing of 1 signal between HV component and the another (become open loop)?

[@InsideEVTraining]

Hello Ali, Apologies for the delayed response. I hope I have correctly understood your question. In the interlock system, there is no open loop. When the HV connectors are closed, the individual electrical resistors, which are connected in parallel to each individual connector, are bypassed. However, when a HV connector or the HV service plug is opened, the current of the interlock passes through the resistor, resulting in a different voltage drop. By analyzing this output voltage of the interlock, the BMS (Battery Management System) can determine that the HV circuit has been opened at a specific point. Upon detection of this, the flow of current to the HV relays is halted, causing the magnetic field to collapse and the HV relays to open.

[@alisamehmohamed2020]

@Inside EV Training - with Daniel and Chris Thanks a lot 😊 now it's clear

[@abhishekupadhyay3690]

Hi.. One question.. What if signal generator has not enough power to send current and which affect the voltage across connector and which feels like its open. How do we ensure signal gemerator has enough power.. Or How signal generator gets charge?

[@InsideEVTraining]

If you have a loss of power, this will lead properly to critical interlock failure, which maybe will shut down the HV system. I can't say it for any case, but basically the BMS will power the interlock.