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Identifying contactor clicks

Discussion in 'Model S' started by whitecotton, Jan 1, 2016.

  1. whitecotton

    whitecotton Member

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    Does anyone have an idea on the amount of contractors or the wiring pattern involved in the Model S. I noticed when I plug in my car the amount of clicks is more frequent then when I walk up to the vehicle to enter and then drive. I also noticed when I pre heated the car today (50 degree) outside temperature it sounded as though the coolant pumps or some else up front were running.
     
  2. roblab

    roblab Active Member

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    Sounds normal. And after 3 years, the contact noises won't mean much. You get used to it. You should hear more clicks when you plug in than when you drive. Heat is by heat pump (A/C) I think, so you should hear compressors running. After a while you will worry if it doesn't click and hum. :smile:
     
  3. whitecotton

    whitecotton Member

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    I've already concluded its smarter than me so I try not to worry, however with my curious mind when it comes to mechanics (particularly Tesla mechanics) I can't help but wonder.
     
  4. CHG-ON

    CHG-ON Still in love after all these miles

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    My car makes all sorts of crazy sounds when sitting in the garage. It moans, groans, clicks and hums. It also self levels periodically. My friends are baffled by it and I find it very amusing. And software updates are even better. My neighbors used to ask what the heck was going on in my garage in the middle of night.
     
  5. Caligula

    Caligula Member

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    Your neighbors can hear your car while its inside the garage?
     
  6. apacheguy

    apacheguy Sig 255, VIN 320

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    When you plug in at night the contactors fully cycle (close, open). When you open the car door they only close.
     
  7. Ingineer

    Ingineer Electrical Engineer

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    There are basically 3 contactors (2 mains and one small relay) that are located in the pack. The small one is used for precharge, and usually you'll hear a clunk ... clack when it precharges, then closes. When it opens just one clunk as both drop out.

    The coolant pumps (3) come on at full speed initially, then slow down to idle when the car first powers up.

    There is no heat-pump mode in the Model S (unfortunately), but the A/C will run in the winder for cabin humidification.

    There is also a line relay and a precharge relay in each charger (if you have 2) located under the rear seat.

    When Supercharging, there are 2 more contactors also located under the rear seat that close. So there is a total of 4 large contactors, and a lot of small relays.
     
  8. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    If I try translating that into English will you let me know if I've done it correctly? As follows:

    "When the small contactor opens for a precharge, what you'll hear is a single 'clunk', as both legs of the contactor drop out simultaneously."

    That's the best I've been able to do. Am I close? Is "legs" an appropriate term?
     
  9. whitecotton

    whitecotton Member

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    What exactly does the pre charge relay do?
     
  10. Ingineer

    Ingineer Electrical Engineer

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    The devices that use high-voltage have storage capacitors in them. Such as the Drive Inverter, Charger, DC-DC converter, etc. If the contactor were to just close and provide full battery power to these devices, there would be massive inrush current as the pack tries to fill the hungry capacitors and this would be very bad for the contactor's contacts (arcing). So the car closes the precharge relay which puts a resistor across one contactor (still open), and then the close the other contactor, wait and watch the voltage come up (relatively slowly) on the HV rails, then when it's equal to battery voltage they close the remaining contactor.

    In the event of a fault, such as a short on the HV rails, the precharge resistor will never allow much current, so the rails will stay low, the car will detect this and can re-open the first contactor.

    When the car goes to sleep, it opens the contactors together. It may also have a method to safely discharge the HV rails, such as by connecting the precharge resistor across the rails or by instructing the Drive Inverter to use power. (I have not determined this yet)
     
  11. apacheguy

    apacheguy Sig 255, VIN 320

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    @Ingineer - The Model S used to open contactors in quick succession. Somewhere in 6.x they changed the contactor behavior such that one opens followed by about 30 s until the other opens. Is there any benefit to delaying the opening?
     

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