Kilovac contactor has a high resistance

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Alibro
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Kilovac contactor has a high resistance

Post by Alibro »

Hi guys
Just question about the used kilovac contactors from Israel that were being sold on ebay. I bought two over a year ago and only today got round to testing them and one of them has a resistance of between 10R and 1kR across the main terminals when activated with 12V. It is pretty random and shows a different resistance every time I trigger it, also the resistance tends to drift down but the other is showing 0 ohms every time.
First is this normal and will it be fine under load?
And second if not I have eight contactors from VW eGolf battery packs which draw around 0.5A at 12V so would the economisers that came with the kilovac contactors be suitable to use with the VW ones? Or is it possible the economisers are causing the problem?

Thanks
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joromy
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Re: Kilovac contactor has a high resistance

Post by joromy »

I would not trust it, trow it away!
A contactor should always show 0 ohm, if it's closing properly, with right voltage and working economizer.
You say you could use the economizer on the other contactor, then you could try to bypass the economizer and connect 12V directly on the Kilovac coil? Just for testing. Be aware that some contactors have two coils, one for closing and the other for holding.
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Alibro
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Re: Kilovac contactor has a high resistance

Post by Alibro »

Thanks for your reply. To be honest I now don't trust either contactor so will not be using them.

This is my first build so everything is new to me so sorry for the newby questions.
I'm having trouble finding information on how best to use the VW contactors. They have no econonisers and draw around 600mA at 14V which I assume is enough to make them overheat and shorten their life. I did some testing and they seem happy to operate at 8V and draw around 340mA
I assume VW reduce the voltage to the them after they have triggered so how do others use these contactors?
Should I use a dc to dc converter to reduce the voltage or just use them at full battery voltage and not worry?

I'm asking this because I only have two economisers and may need 3 or 4 contactors.
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alehandro
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Re: Kilovac contactor has a high resistance

Post by alehandro »

Alibro wrote: Thu Jun 30, 2022 7:54 am Thanks for your reply. To be honest I now don't trust either contactor so will not be using them.

This is my first build so everything is new to me so sorry for the newby questions.
I'm having trouble finding information on how best to use the VW contactors. They have no econonisers and draw around 600mA at 14V which I assume is enough to make them overheat and shorten their life. I did some testing and they seem happy to operate at 8V and draw around 340mA
I assume VW reduce the voltage to the them after they have triggered so how do others use these contactors?
Should I use a dc to dc converter to reduce the voltage or just use them at full battery voltage and not worry?

I'm asking this because I only have two economisers and may need 3 or 4 contactors.
You may be able to operate a contactor with a reduced voltage in static mode, but the voltage of 8 volts may not be enough to hold when shaking. I am using the new EV200AAANA 1618002-7 and there is no problem with them.
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Re: Kilovac contactor has a high resistance

Post by Alibro »

alehandro wrote: Sun Jul 03, 2022 7:19 am
Alibro wrote: Thu Jun 30, 2022 7:54 am Thanks for your reply. To be honest I now don't trust either contactor so will not be using them.

This is my first build so everything is new to me so sorry for the newby questions.
I'm having trouble finding information on how best to use the VW contactors. They have no econonisers and draw around 600mA at 14V which I assume is enough to make them overheat and shorten their life. I did some testing and they seem happy to operate at 8V and draw around 340mA
I assume VW reduce the voltage to the them after they have triggered so how do others use these contactors?
Should I use a dc to dc converter to reduce the voltage or just use them at full battery voltage and not worry?

I'm asking this because I only have two economisers and may need 3 or 4 contactors.
You may be able to operate a contactor with a reduced voltage in static mode, but the voltage of 8 volts may not be enough to hold when shaking. I am using the new EV200AAANA 1618002-7 and there is no problem with them.
I have one of those on order from Aliexpress to see if they are worth buying. They look identical to the ones available on eBay for 2, 3, and 4 times the price. I suspect unless you're buying from RS or similar reputable supplier they all come from the same Chinese copy shop.
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celeron55
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Re: Kilovac contactor has a high resistance

Post by celeron55 »

Personally I'd trust a used one more than a Chinese clone.

But if it's showing high resistance it's not good.

You could measure the coil input current to see whether that looks like what it's supposed to.

You could try bringing the contacts back to life by doing something relatively stupid like shorting out a small lead acid battery in short pulses using the contactor, switching a mains powered heater or something else that would wear some new surface to the contacts. But I would definitely not recommend it as anything other than a science experiment.
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Re: Kilovac contactor has a high resistance

Post by Alibro »

celeron55 wrote: Mon Jul 04, 2022 4:35 pm Personally I'd trust a used one more than a Chinese clone.

But if it's showing high resistance it's not good.

You could measure the coil input current to see whether that looks like what it's supposed to.

You could try bringing the contacts back to life by doing something relatively stupid like shorting out a small lead acid battery in short pulses using the contactor, switching a mains powered heater or something else that would wear some new surface to the contacts. But I would definitely not recommend it as anything other than a science experiment.
It is already in the bin so it won't be a problem
As for using the VW contactors have you any suggestions about lowering the current draw? 600mA seems like a lot to be drawing for long periods so I was thinking of reducing the Voltage to them. They seem happy at 8V but maybe 9V - 10V would be safer. I haven't got my Outlander PHEV charger/dc to dc going yet so am not certain what voltage it will supply but am assuming around 14V.
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Re: Kilovac contactor has a high resistance

Post by johu »

I found some Chinese relays to still hang on at 2.5V https://openinverter.org/forum/viewtopic.php?t=531
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celeron55
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Re: Kilovac contactor has a high resistance

Post by celeron55 »

Alibro wrote: Mon Jul 04, 2022 7:07 pm As for using the VW contactors have you any suggestions about lowering the current draw? 600mA seems like a lot to be drawing for long periods so I was thinking of reducing the Voltage to them. They seem happy at 8V but maybe 9V - 10V would be safer. I haven't got my Outlander PHEV charger/dc to dc going yet so am not certain what voltage it will supply but am assuming around 14V.
Generally a contactor without an internal economizer is specified to require about 100ms of full voltage (usually 9-15V for 12V models) when switching on, and about half of that (5-7V) afterwards.

The release voltage in practice will be just a couple of volts, but it won't handle shaking or full current at a few volts. It also will unreliably switch on at much lower than the specified minimum, depending on temperature, orientation and vibration.

Sometimes it's possible to drive uneconomized contactors within spec by using a single voltage. Such voltage will be around 8V for 12V models.

A rule of thumb for me is, if a contactor takes in more than let's say 7W (for a GV200 sized one), that's probably an issue. Depends on the size of the coil of course. A big coil can dissipate more heat.
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Re: Kilovac contactor has a high resistance

Post by Alibro »

celeron55 wrote: Tue Jul 05, 2022 9:10 am
Alibro wrote: Mon Jul 04, 2022 7:07 pm As for using the VW contactors have you any suggestions about lowering the current draw? 600mA seems like a lot to be drawing for long periods so I was thinking of reducing the Voltage to them. They seem happy at 8V but maybe 9V - 10V would be safer. I haven't got my Outlander PHEV charger/dc to dc going yet so am not certain what voltage it will supply but am assuming around 14V.
Generally a contactor without an internal economizer is specified to require about 100ms of full voltage (usually 9-15V for 12V models) when switching on, and about half of that (5-7V) afterwards.

The release voltage in practice will be just a couple of volts, but it won't handle shaking or full current at a few volts. It also will unreliably switch on at much lower than the specified minimum, depending on temperature, orientation and vibration.

Sometimes it's possible to drive uneconomized contactors within spec by using a single voltage. Such voltage will be around 8V for 12V models.

A rule of thumb for me is, if a contactor takes in more than let's say 7W (for a GV200 sized one), that's probably an issue. Depends on the size of the coil of course. A big coil can dissipate more heat.
Assuming my battery voltage will be 14V while the dc-dc is on, my VW contactors will be drawing 8.5W so from what you are saying it is too much. If I used a small dc to dc converter I can set the voltage to anything I want so if I set it to 10V the contactors would be drawing 6W which sounds more reasonable. If I set it to 9V they will draw 5.4W but maybe it is too close to the minimum safe voltage.
johu wrote: Tue Jul 05, 2022 8:54 am I found some Chinese relays to still hang on at 2.5V https://openinverter.org/forum/viewtopic.php?t=531
Thanks Johannas, I had been searching for a thread like this one for ages but probably used the wrong search terms.
Would you use a simple circuit like this for your main contactors? I can't think why not but I don't know what I don't know. :D

BTW I tried the economiser that was screwed to the Kilovac contactor with one of the VW contactors and it didn't work. The contactor clicked closed briefly then opened again.
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Re: Kilovac contactor has a high resistance

Post by Alibro »

I found an interesting article here.
https://www.electronicdesign.com/power- ... ay-drivers

However I think for simplicity (unless someone advises against it) I will go with a constant voltage dc to dc converter and will set the voltage to between 9V and 10V. I already have several suitable modules so will go with what I already have.

Maybe I'll use this one as it is suitable for 5A.
IMG_20220705_104655417.jpg
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Re: Kilovac contactor has a high resistance

Post by johu »

Alibro wrote: Tue Jul 05, 2022 9:29 am Would you use a simple circuit like this for your main contactors? I can't think why not but I don't know what I don't know. :D
Simplicity is king ;) I used it on my charge port contactors which have to handle 125A. Wouldn't hesitate to use it on main contactors but Panasonic relays only take in 300mA@12V so couldn't be bothered.

Never thought contactors could shake loose but celeron has a point there. For charge port relays it doesn't matter as the car is then stationary
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Re: Kilovac contactor has a high resistance

Post by m.art.y »

Trying to understand what's the main issue here, power consumption or the contactor overheating? I'm also using kilovacs, large ones for main contactors have economisers, I also use smaller kilovacs that don't appear to have economisers for dcdc. When I measured amp draw smaller ones seemed to draw about the same as the large ones - around half an amp. Will that be an issue long term? If reducing voltage helps adding a diode could drop the voltage by about 1-2v?
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Re: Kilovac contactor has a high resistance

Post by Alibro »

m.art.y wrote: Tue Jul 05, 2022 7:27 pm Trying to understand what's the main issue here, power consumption or the contactor overheating? I'm also using kilovacs, large ones for main contactors have economisers, I also use smaller kilovacs that don't appear to have economisers for dcdc. When I measured amp draw smaller ones seemed to draw about the same as the large ones - around half an amp. Will that be an issue long term? If reducing voltage helps adding a diode could drop the voltage by about 1-2v?
I read on the internet (so it must be true) that the VW contactors do not have economisers but rather have their voltage lowered by PWM after triggering so that they don't overheat shortening their life. I'm not concerned about power consumption as it is insignificant in an EV drawing many kW.
I have never used them before so can only go by what I'm being told.
At the moment while at 14V they are drawing 600mA so 8.4W, I'd like to bring the voltage down to around 10V where they are drawing 400mA so around 4W.

Hopefully in a few months I will be able to tell you if vibration is an issue but as VW lower the voltage to them once triggered I can't see why it would be.
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Re: Kilovac contactor has a high resistance

Post by alehandro »

For example, I also successfully use high-current solid-state DC relays, 60 A for pre-charging without a radiator and 400A with a large radiator for the charging port. And I like such an inexpensive solution bought on Aliexpress. https://www.aliexpress.com/snapshot/0.h ... 1632807976
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