isolation monitoring

Technical discussion on converting internal combustion to electric
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smokinjoe
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isolation monitoring

Post by smokinjoe »

Hi Guys,

I was wondering what people were using to monitor "leakage current" as per the ncop guideline. My bms doesn't have anything built in like the zeva evms. I've been looking at the bender iso165c-1 but wanted to see if there are other solutions out there before I go down that road.

Cheers,
Joe
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brendon_m
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Re: isolation monitoring

Post by brendon_m »

Personally I didn't do anything. I did a manual measurement for the engineer and that's about it. It's a "may" do not a "must" do.
smokinjoe
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Re: isolation monitoring

Post by smokinjoe »

That's fair enough, your conversion is a fairly low voltage right? I'm running a 360v nominal pack and wouldn't mind something there for peace of mind
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brendon_m
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Re: isolation monitoring

Post by brendon_m »

Yeah mine was only 100V so not really high risk.
I wonder if the leakage detector from a leaf or imiev could be used.
smokinjoe
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Re: isolation monitoring

Post by smokinjoe »

Good question, might have to look into that.
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brendon_m
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Re: isolation monitoring

Post by brendon_m »

Had a bit of a hunt through diagrams and I couldn't find much on the leaf but the imiev one I believe just switches a wire to ground when a fault is detected.
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6 wires
1x Ignition feed
2x earth's
1x HV
1x "switch to ground" signal
1x circuit check? To make sure the sensor is working?
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brendon_m
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Re: isolation monitoring

Post by brendon_m »

Screenshot_20210323-135817.png
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Screenshot_20210323-140103.png
Screenshot_20210323-140103.png (408.35 KiB) Viewed 436 times
Interesting that 2 separate diagrams on the russian site give 2 different wiring configurations.
One with 2x grounds and the other with 2x HV sense wires.
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brendon_m
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Re: isolation monitoring

Post by brendon_m »

Judgement Criterion
If the traction battery ground fault detector input is not turned ON within 5.5 seconds after the pre-check signal is turned ON from OFF.
or

If the traction battery ground fault detector input is not turned OFF within 2.5 seconds after the pre-check signal is turned OFF from ON.
So the diagnositic page answers the operation question.
Give the unit an earth on the precheck wire and within 5.5 seconds it will ground the sense wire if all is ok.
(And if it doesn't remove the earth from the sense wire within 2.5 seconds of the precheck wire being disconnected then throw a code.)

Should be fairly easy to wire that into some sort of alarm on the car
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coulomb
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Re: isolation monitoring

Post by coulomb »

I suspect that the iMiEV solution will be expensive and difficult to source. All you need are some high voltage relays and a large resistor or two . I forget the details and I'm AFK. There might be some details on Webber's MX-5 build topic.
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smokinjoe
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Re: isolation monitoring

Post by smokinjoe »

Cheers Brendan and Coulomb, I'll look into both. 👍
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Bryce
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Re: isolation monitoring

Post by Bryce »

Hi Joe - I've used the Bender IR125 unit before with great success. The uni FSAE EV race teams must also include a ground-fault detection system and primarily use Bender units. Your local AEVA branch should have contacts with the local uni team to get info on them.
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brendon_m
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Re: isolation monitoring

Post by brendon_m »

That one is only rated to 308Vdc, but at least it looks a lot less specialized (read:cheaper) than the iso165c that was first mentioned
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4Springs
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Re: isolation monitoring

Post by 4Springs »

When I converted my vehicle I found a process described where you use the traction pack voltage and a test resistor to find the leakage current. It's a pretty simple test that uses a normal multimeter. You can read about it (and see my video) here: https://christopherwalkden.id.au/earth- ... verted-ev/
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