Isolation Monitor - Suggestions?

[P.S.Mangelsdorf]

Recently, NHRA rules have changed and now require an active isolation monitor for the HV battery.

I'm looking for a simple isolation monitor that will trigger a 12V signal if there is a fault. I don't really need anything else, as I would like to just trigger the required lights/alarms.

I cannot seem to find something that will do the trick. Does anyone have ideas or sources for a simple isolation monitor?

[Bigpie]

There's not many options. At least that I've come across. I've recently reverse engineered the golf GTE isolation monitor, but not yet put it to work.

[muehlpower]

What about that? Unfortunately it needs 24V supply, so it needs a voltage doubler to use it in the car.

[tom91]

What is considered a fault? what is the minimum resistance level per V?

Bender does some nice units https://www.bender-uk.com/products/insu ... iso165c-1/

[zippy500]

I was looking at these some time ago on Alibaba.

https://www.alibaba.com/product-detail/ ... 182eCOrQnl

[tom91]

I was looking at these some time ago on Alibaba.

https://www.alibaba.com/product-detail/ ... 182eCOrQnl

Those work too, just the connectors and such are not really up to "spec". But they work as it says in the datasheet, have bench tested them.

[Pete9008]

Those work too, just the connectors and such are not really up to "spec". But they work as it says in the datasheet, have bench tested them.

Have you had a look inside to see what they are like? (curious whether the spec inside is better than the connectors)

[muehlpower]

Doesn't the M3 PCS or your BMS do an isolation check and output it over CAN. Then you could have an arduino or similar turn on a lamp. To prove the function, a test switch with xxxkOhm from a HV line to the vehicle ground could be installed.

[P.S.Mangelsdorf]

Thanks all for the input.

I keep getting 502 Bad Gateway on Bender's sites; I've tried on two computers and 3 browsers. I can get to their contact page, so I'll try asking them for help.

The specific text of the rule is as follows

An IMD (Insulation Monitoring Device) is mandatory. The IMD
monitors the chassis for high voltage shorting. The IMD may be
stand alone or part of the electronic subsystem. The IMD must be
capable of commanding, either directly or indirectly through the
Vehicle Control Unit (VCU) or other computer systems, the vehicle
status lights to turn red if high voltage is present on the chassis.
The IMD must stay powered even when the Master Battery
Disconnect is deactivated (pushed off) to alert track officials of a
potential high voltage short on the vehicle. It is the responsibility
of the owner/driver to understand the IMD system and have the
means to test and demonstrate its functionality upon request

Mandatory – all cars must have an LED light visible from front,
rear, left, right and to the driver on interior of the vehicle. The
lights must illuminate GREEN in color if high voltage is active andall systems are functioning properly (SAFE). The LED lights must
illuminate RED in color if the IMD or any other monitoring system
has triggered a fault (DANGER). Safety Indicator lights must
remain illuminated after 12V Master Battery Disconnect has been
pushed off. A minimum of 1/2” LED required. LED lighting must
be clearly visible at a minimum of 100 feet from vehicle in direct
sunlight. Vehicles must also be equipped with an audible alarm,
similar to an automobile back-up alarm with a minimum of 90
decibels. The audible alarm must be activated when the LED is
illuminated RED and the systems has triggered a fault (DANGER).

The model 3 PCS may do an iso check, but a) mine does not want to send CAN messages right now, and b) I'm very uncomfortable with the part of the rule requiring the vehicle status lights to remain on even when the vehicle master disconnect has been actuated*, so I'd like to keep this as simple as possible. Ideally, just the IMD and BMS would stay powered, and then use two or three relays to activate the lights.

(*I don't like the rule because track personnel are used to "off means off" and are nervous enough around EVs. Plus the new rules do not indicate if the vehicle is turned on and may move. The previous rule (illuminated red triangle if the car was turned on) was much more straightforward in the event of an accident.)

[muehlpower]

I think I found the perfect part. It's also from bender. Especially for EVs. In Germany it costs 280€

[jrbe]

Thanks all for the input.

I keep getting 502 Bad Gateway on Bender's sites; I've tried on two computers and 3 browsers. I can get to their contact page, so I'll try asking them for help.

The specific text of the rule is as follows




The model 3 PCS may do an iso check, but a) mine does not want to send CAN messages right now, and b) I'm very uncomfortable with the part of the rule requiring the vehicle status lights to remain on even when the vehicle master disconnect has been actuated*, so I'd like to keep this as simple as possible. Ideally, just the IMD and BMS would stay powered, and then use two or three relays to activate the lights.

(*I don't like the rule because track personnel are used to "off means off" and are nervous enough around EVs. Plus the new rules do not indicate if the vehicle is turned on and may move. The previous rule (illuminated red triangle if the car was turned on) was much more straightforward in the event of an accident.)

It makes sense for the safety personnel. If there's an issue and the pack is shorted to the chassis without the warning led there's no warning for them of the danger they're running up to.
Is there a time requirement for how long the warning system must stay active with the battery shutoffs off? A small 12v battery should do the trick to power the isolation check system after its off.

Thanks for sharing the isolation monitor muehlpower! This was something that seems to be missing from a lot of high voltage swaps. That looks like a great solution.

[P.S.Mangelsdorf]

I think I found the perfect part. It's also from bender. Especially for EVs. In Germany it costs 280€

Yeah, that looks like it will work. I've requested a quote for one here in the US.

[RetroZero]

What is considered a fault? what is the minimum resistance level per V?


The isolation resistance of the complete HV system to ground with the contactors closed should be >500Ω/V and hence for a battery pack its resistance target must be specified by the HV System designer, typically >1,500kΩ.

[RetroZero]

BTW, I have contacted a company specialising in HV isolation components for a bulk buy of 10. Let me know if anyone is interested whilst I wait for their reply.

https://www.sensata.com/products/insula ... mlp-module

[EV_Builder]

Mhhh interesting what's the price?

[zippy500]

[EV_Builder]

And all of that on a metal workbench? / Table?

[RetroZero]

There's not many options. At least that I've come across. I've recently reverse engineered the golf GTE isolation monitor, but not yet put it to work.

I have an e tron one I'm playing with, but mostly to learn to understand CAN. There's no part number on it so ordering from a dealership or manufacturer will not be happening. I am learning repeatability is a key to getting projects safely on the road, along with not re-enventing the wheel. I will see how much they cost before talking too soon

[Zieg]

BTW, I have contacted a company specialising in HV isolation components for a bulk buy of 10. Let me know if anyone is interested whilst I wait for their reply.

https://www.sensata.com/products/insula ... mlp-module

Did you get a reply?

[RetroZero]

Funny you mention that. I'm sitting looking at it today. This is the reply I received.

Thanks for your request. Please can you let me know more project details, end customer, application and any yearly demand?
Please can you also let me know complete part number you need, see attached the datasheet

[P.S.Mangelsdorf]

When I reached out to Bender they replied and seemed eager to give a quote until I told them I was buying as an individual and there was no company name to put on the quote. Radio silence since.

[muehlpower]

I think you can buy it here in USA. Note the differences. The "-1" version has 2 digital outputs with which you can switch your lights directly.

https://store.neweagle.net/shop/our-mar ... evice-imd/

[RetroZero]

I applied with my company number

[RetroZero]

So I got a response. If ordered via my company, looks like in the range of 500€ since it's low volume orders. Looking into it with mire details, it might be able to replace the isabellenhütte current sensor - 2 in 1. If so, it becomes a viable item in my little ev experience.

[muehlpower]

In the EU you can buy it for €290 if the version without digital outputs and with 250 kBaud is sufficient.
I was also wondering if one of the two voltage inputs can be used to monitor the DC charging port
https://www.conrad.de/de/p/bender-iso16 ... 6+Haushalt