[Jeremy Harris]

If I had to guess, then I'd suggest that the issue most probably relates to the somewhere other than the battery cells themselves, most probably something else on the HVDC bus, as already suggested, or the battery management system. There's a load of cobblers in some of the earlier posts, referring to charging and the absurd idea that a 500 V IR test could cause damage, it can't, and is part of the manufacturer's diagnostics anyway, and manufacturers don't tend to have diagnostic procedures that risk damage.

As above, a decent HEVRA place may well be able to fix this, and in all probability it won't mean replacing the battery pack cells, but getting hold of spares to fix it may be a challenge. These cars weren't sold in huge numbers, and were never that well supported by Mitsubishi UK.

 

[freddym]

OP, just a few hints here.

Place close attention to any advice from DBMandrake and Eddie49 as both have had long associations with iMiev and clones like CZero. Also, these two are sound and very helpful.

You probably also want to join MyImiev dot com forum and search for any similar symptoms there.

HobDrive (paid version) works well as a poor mans diagnostic system on these cars.

 

[Duckie]

Has the car impacted anything, or been through a flood or ford?

I'd be jacking it up onto axle stands, and getting under to check for damage.

The roof was damaged about passanger rear door in the storm and is waiting to be repaired.
But I find it hard to imagine that causing the issue.
But thanks for the thought

 

[DBMandrake]

The roof was damaged about passanger rear door in the storm and is waiting to be repaired.
But I find it hard to imagine that causing the issue.
But thanks for the thought

Hmm...

Are you aware that several of the car's main control ECU's including the BMU (main battery management unit) are located under the rear passenger seat bench ? If they have had water damage it might be a contributing factor to any malfunctions although in theory wouldn't directly cause this insulation test failure.

In any case you need to remove the rear seat base and check these ECU's are OK. I can't quite remember how it comes off but it's very easy - I think there's a couple of tabs you pull under the front edges of the seat base and the whole base slides forward and comes out.

The ECU's are then located under a protective metal shroud - remove this shroud and check for any signs of water damage of these ECU's and their cabling connectors... As I say I don't think this is responsible for the specific problem you're seeing but if water has been getting in there and seeping down onto the ECU's you're better to know about it now rather than later as it could result in problems in the future...

 

[Stinsy]

If I had to guess, then I'd suggest that the issue most probably relates to the somewhere other than the battery cells themselves, most probably something else on the HVDC bus, as already suggested, or the battery management system. There's a load of cobblers in some of the earlier posts, referring to charging and the absurd idea that a 500 V IR test could cause damage, it can't, and is part of the manufacturer's diagnostics anyway, and manufacturers don't tend to have diagnostic procedures that risk damage.

As above, a decent HEVRA place may well be able to fix this, and in all probability it won't mean replacing the battery pack cells, but getting hold of spares to fix it may be a challenge. These cars weren't sold in huge numbers, and were never that well supported by Mitsubishi UK.

I’m imagining a fault where the positive side of the traction battery isn’t isolated properly from the positive side of the 12V system. This is a problem but you won’t see undesirable consequences because the negative side of the traction battery is isolated from the chassis. However if you then perform a 500V insulation resistance test between the traction battery and the chassis, you’ve then just put 500V through every 12V component…

 

[Jeremy Harris]

I’m imagining a fault where the positive side of the traction battery isn’t isolated properly from the positive side of the 12V system. This is a problem but you won’t see undesirable consequences because the negative side of the traction battery is isolated from the chassis. However if you then perform a 500V insulation resistance test between the traction battery and the chassis, you’ve then just put 500V through every 12V component…

The 12 V bus has to be protected against over-voltage from any component failure by design. The safety consequences of the HV bus voltage getting on to any of the components that the user can touch would be horrific, so manufacturers go to great lengths to ensure it cannot happen, even going so far as to have things like pyrofuses that isolate the HV battery in the event of something serious going wrong. In this case, an IR test is a normal diagnostic test, as it is for several other EVs.

 

[freddym]

I’m imagining a fault where the positive side of the traction battery isn’t isolated properly from the positive side of the 12V system. This is a problem but you won’t see undesirable consequences because the negative side of the traction battery is isolated from the chassis. However if you then perform a 500V insulation resistance test between the traction battery and the chassis, you’ve then just put 500V through every 12V component…

No, what you describe is not a thing.

The discharged traction battery voltage is way over 200V.

This alone would destroy most components on the 12v system.

 

[Stinsy]

No, what you describe is not a thing.

The discharged traction battery voltage is way over 200V.

This alone would destroy most components on the 12v system.

That isn’t how electricity works! The traction battery is isolated from the chassis. A 12V component can happily sit there connected to the +ve side of the 400V (or whatever) traction battery. It is only when someone comes along and runs an insulation resistance test (typically 250, 500, or 1000V) between the traction battery cables and the chassis that the component gets fried.

 

[Jeremy Harris]

That isn’t how electricity works! The traction battery is isolated from the chassis. A 12V component can happily sit there connected to the +ve side of the 400V (or whatever) traction battery. It is only when someone comes along and runs an insulation resistance test (typically 250, 500, or 1000V) between the traction battery cables and the chassis that the component gets fried.

Do you REALLY think that a manufacturer comes up with a diagnostic test schedule and doesn't ensure that it can be conducted safely?

It's like me doing an IR test during an EICR. It's very common to have electronic stuff permanently wired now (LED drivers, alarm systems, etc). Doesn't mean I can't check IR at 500 V, it just means using the defined safe test method where sensitive kit may be connected to the circuit under test.

 

[Stinsy]

Do you REALLY think that a manufacturer comes up with a diagnostic test schedule and doesn't ensure that it can be conducted safely?

It's like me doing an IR test during an EICR. It's very common to have electronic stuff permanently wired now (LED drivers, alarm systems, etc). Doesn't mean I can't check IR at 500 V, it just means using the defined safe test method where sensitive kit may be connected to the circuit under test.

That is entirely different! You’re checking domestic wiring and I guess you’re testing L+N to earth. There will be no ELV equipment in a house that use earth as the negative connection. In fact all ELV DC equipment in a house will be isolated from Earth. Therefore there is no possibility of damaging ELV DC components (eg alarms, USB chargers, or whatever) in a house.

Whereas an EV has a huge number of ELV DC components, with the negative terminal of every component bonded to the chassis. It is an entirely different environment, an IR test from the traction battery cables to the chassis has the potential to destroy or damage ELV components if a fault exists.

Maybe I’m overblowing the risk. This test is described in the workshop manual so the manufacturer must be confident it is safe. Interesting that car dealerships will now have a MFT on a shelf somewhere. I wonder how confident the technicians are in it’s use?

 

[Jeremy Harris]

I repeat, do you REALLY, as in REALLY and TRULY, believe that any manufacturer would be so incredibly stupid as to include a diagnostic test that risked damage to the car?

This was a standard diagnostic test. IR testing is standard and commonplace on EVs, has been for years, because leakage from the HV side to the chassis from a fault is clearly a possible fault, some might say a fairly common fault with some EVs (some early Renault motors, for example). Manufacturers produce test schedules and diagnostic equipment at the same time that they design the car, they don't just pluck random ideas out of thin air and assume someone at a dealership will work out how to do testing safely using whatever test gear they have to hand.

Anyway, the low voltage side will be electrically isolated from the HV side at least up to the maximum voltage of the HV system, plus a margin. No manufacturer is going to include a conductive path that could break down and risk putting a dangerous voltage on to parts that the user might touch (controls, 12 V and USB ports, etc).

 

[Norniron man]

Hmm yes normally the designers will try to comply with IR test rules but the good Mr Murphy's rules will also kick in occasionally. I lost count of the number of service calls we got after some crowd doing the usual audit got loose with a megger tester in some computer room or office ! Of course you can claim well that piece of kit was about to fail n the test simply pushed it over the limit (dust dirt and damp or cable stress/damage/age etc).
Just my tuppence worth ,but have you seen inside a Chinese made toaster? power connectors 3mm from the steel case etc!

 

[Jeremy Harris]

Hmm yes normally the designers will try to comply with IR test rules but the good Mr Murphy's rules will also kick in occasionally. I lost count of the number of service calls we got after some crowd doing the usual audit got loose with a megger tester in some computer room or office ! Of course you can claim well that piece of kit was about to fail n the test simply pushed it over the limit (dust dirt and damp or cable stress/damage/age etc).
Just my tuppence worth ,but have you seen inside a Chinese made toaster? power connectors 3mm from the steel case etc!

Even really cheap opto isolators happily work at well over 1kV. When I connected a Raspberry Pi up to the house inverter I used a cheap (as in ~£4) RS485/MODBUS adapter and even that had opto isolators rated to handle 1.5 kV protecting the data lines and isolating the inverter from the RPi working at 5 V/3.3 V. Same goes for the EV battery packs and controllers I've built, all had opto isolators, so that data from the BMS was electrically isolated from the battery terminals and the data lines and FET drive signals were isolated from the relatively high voltage DC bus.

I really cannot believe that any EV manufacturer would publish a diagnostic test schedule and issue dealers with diagnostic equipment that had even the slightest chance of damaging the vehicle under test, anyway, leaving aside the fact that the manufacturer will have had exactly the same safety concerns that I had, and will make certain there is galvanic isolation between all the low voltage parts and the high voltage parts.

 

[freddym]

I'm firmly of the "gut feel" that there is a cabling problem somewhere. It could be the HV cabling itself. It could be the terminations. It could be a HV component such as the aircon compressor which has not been systematically tested by elimination by the dealer. (HV devices include motor invertor, PTC heater, aircon compressor, Charger/DC-DC converter)

HV devices also include the Chademo charging port.

All of this can be tested without removing the battery from the car.

Then if my gut feel is wrong, presumably it would be necessary to remove the battery from the car to get at the cell monitoring boards.

Can anyone advise the OP of a HEVRA garage that has an interest in the iMievs (and clones)?