HV Contactor Longevity

[Scotty]

The contactor(s) used by Tesla appear to be Csonka Kilovac family of contactor. These are fairly reliable for high voltage, high current applications. They are available with an 'Economizer' circuit board for lower power consumption, and the economizer tends to be the higher failure point of the contactor. They are also available with a second set of low power contacts that can be used to provide isolated verification of contact closure.

I am very familiar with contactor design and use in many electrical vehicles, but I don't have any detailed information on how Tesla implements their contactor(s). On the thread that showed the battery pack being disassembled, it looked to me that there were 2 Kilovac's in the pack. It would have been very nice if Tesla had implemented an access door or panel for the contactor(s) to be accessed and replaced without opening up the whole pack. If I get the opportunity to see a pack as it's opened, I'd sure like to see what options might be available.

Back to contactor operation; they basically isolate or connect the high voltage high current battery pack to the high voltage systems, such as the motor controller, and HVAC system. The load of the contactor doesn't need to be high current; just for it to need to be isolated from the battery pack at certain times, Fault detection can also open the contactor, preventing damage or unintended consequences, such as a runaway condition, or system short or excessive current draw. The console, etc could easily be powered by the DC/DC Converter (but the weakass 12 Volt AGM battery wouldn't last long when discharging). I would also think the DC/DC Converter would not be switched, since the car electrical system (including the security system, 3G, and sleep mode) would quickly drain the 12 V battery.

When the contactor opens and closes, it makes or breaks the current flow. Just like connecting a battery to a load, there will be arcing, and this can pit the contacts, dmaging them. The amount of pitting each time is proportional to the amount of current that will be flowing through the contacts. The opening or closing is defined a s 'make' or 'break'. Higher current will result in shorter time between failure.

As a MS85 owner, the contactor failing, as well as astronomical accident repair costs, are my 2 biggest concerns. While the Kilovac contactors are not too expensive (typically < $300), what Tesla decides to charge for an out of warranty contactor failure, with removing the pack, opening up the pack, replacing it and resealing the pack, could be eye-opening.

Scotty

 

[mibars]

I've certainly done more than 50 launches at 100% throttle. Maybe I'm misunderstanding the rating-speak? What does this mean real-world? Those numbers seem very low for a part warranted for 8 years.

Contactor experiences wear when it is switching, the higher the current that it either connects or interrupts the bigger the wear (actaully interrupting current causes higher wear due to arc being "pulled" between contact points before gap is big enough to stop it). When you are driving it is always closed, no switching is taking place and it happily conducts hundereds of amps to drive unit. It will also survive hundereds of thousands cycles when there is no or very small current being switched, again it applies to the moment of switching, as long as current is removed before disconnecting or applied after contact is made it is fine. But! If it will be disconnected under big load just couple of times its resistance will greatly increase and this will lead to failiure.

Those high current switching is experienced when car goes into emergency mode, eg. when it senses trouble with drive unit.

 

[101bugs]

Scotty, my understanding is Tyco (formerly Kilovac) contactors are not able to handle the Tesla power levels and are being replaced with those from a new supplier. Plus Tyco moved their contactor manufacturing offshore and may have lost some of their quality control.

 

[gavine]

I would prefer a delay engaging the contactor too. My kids frequently won't open the rear doors until after I've closed the front doors, causing an extra cycle. And then when you go back to get groceries, etc, it does it again. In the summer I've taught myself not to close the door until we're completely done.

I noticed recently that there is now a delay in cycling the contactor after exiting the car. I'm not sure about the timing, but I forgot my phone in the car tonight. I went back to get it about 30 seconds (maybe a minute) later and the contactor didn't cycle when I opened the door so it was still closed from when I exited the car. It used to open within a few seconds of closing the door. The beauty of OTA software updates.

 

[ewoodrick]

I've certainly done more than 50 launches at 100% throttle. Maybe I'm misunderstanding the rating-speak? What does this mean real-world? Those numbers seem very low for a part warranted for 8 years.

The contactor should be engaged well before your foot ever hits the accelerator. AFAIK, the motor contactor probably never switches over a few amps, except for in an emergency. The charging contactor probably does more, but even then, I don't think that it is ever full load.

Contactors can generally carry a lot of current when closed. It's the act of opening or closing with high current that hurts. When contactors opens or closes, there tends to be some arcing that occurs. That arcing can leave residue on the contacts and reduce the surface area of electrical contact. If the surface area is too small, the contacts can get hot and weld themselves together.

 

[gavine]

The contactor should be engaged well before your foot ever hits the accelerator. AFAIK, the motor contactor probably never switches over a few amps, except for in an emergency. The charging contactor probably does more, but even then, I don't think that it is ever full load.

Contactors can generally carry a lot of current when closed. It's the act of opening or closing with high current that hurts. When contactors opens or closes, there tends to be some arcing that occurs. That arcing can leave residue on the contacts and reduce the surface area of electrical contact. If the surface area is too small, the contacts can get hot and weld themselves together.

Here’s a video showing how the contactor can be damaged when disconnecting under load. Fast forward to 5:45.

 

[DrTharp]

ALCON,

I had my contractors replaced (not by Tesla due to it being a salvage car). I still get the "Car needs serviced" and i will actually begin to shut down, even though I replaced them. I don't know what else to do and I'm getting a "GTW_w319_contactorImpedance" alert. Does this mean the new contactors I just put in are ineffective? Or is there something else I need to replace? Any insight, intel would be most helpful. Thanks!