# Leaf module testing for Insulation resistance loss



## kennybobby (Aug 10, 2012)

How old is your 12V aux battery? 10.8V is way too low. A weak or worn out aux battery can cause a multitude of issues and faults, which will mostly clear when the aux is replaced. 

Your cells look very good for a 2012, to only be down to 10 bars is remarkable.

Notice how the test voltage is higher at first, then drops. Also the Insulation Resistance test starts at around 40 MOhms, then rises. If you take the voltage divided by the IR, this will give you an idea of the leakage current thru the insulation. From a couple of spot checks, it appears to range from 50 down to 0.5 x 10e-9, i.e. nanoAmps. That's nearly zero. So the voltage and IR tests are consistent and within normal range, not likely to be causing a fault.

The fault is more likely to be from the ground fault detector box or circuit board that monitors this at the system level, and that box is likely is powered from the 12V aux battery. See where i'm going with this?


----------



## cgalpin (Dec 5, 2012)

Thanks for taking the time to reply, I really appreciate it.

I don't know the history of the battery (i bought this car in this condition to learn and try fix for the fun of it) but it does not look original and is ok. I even went and got it tested at auto zone this AM to be sure, but when I took those readings it had been sitting for a few months and I had not charged it. It charged fine and I redid my testing with it fully charged as well as with a trickle charger connected and it did not help. It has held a charge fine (was 12.5v today after sitting for about a month).

So a bit of history that I do know. This was taken to a Nissan dealer who looked at it and determined the problem was in the battery pack and didn't want to work on it without an open checkbook due to a rusty undercarriage (it's rusty underneath for sure). I am perhaps guilty of trusting this diagnosis more than I should, and I do know there are other components that can cause this fault, but since I'm in it for the learning experience, and the battery interests me the most, I dug into the battery, perhaps foolishly 

But your interpretation of the battery readings is encouraging - enough to feel like it's worth re-assembling the battery pack and putting it back into the car - at least for long enough to find the source of the problem and get it to take a charge, which is something I'd like to be able to verify works fine one way or the other. I think in the end I'll part it anyway since it's not nice enough to keep and given the rust would not want to pass this on to someone else and become a liability. I don't need/want a leaf myself (I have a Tesla Model 3) and the range isn't enough if I ever start commuting again. This might be a good first step (starter pack) in my conversion project before shelling out for a much more expensive tesla pack that I really want though. But I would like the satisfaction of figuring out the problem and verifying everything else works well. It drove fine, so charging is the only other thing I want to get working.

I guess let me ask this since I am curious - why do those rear cells show voltage from the terminals to the case, and have an order of magnitude lower MOhm reading in the IR tests than the side ones? That seems a bit fishy to me. But I guess as long as it's not unsafe (or causing this damn fault), they seem fine to me.

Regarding further troubleshooting steps, I know the A/C is not blowing cold, and someone on the forums said the A/C compressor could be the cause of this fault if the refrigerant is contaminated (or maybe low). Do you know if the car will take a charge with the A/C system unplugged? I don't want to add refrigerant if I am going to just be taking it apart again (I'd want to take it to a shop to be evacuated and properly disposed of). In other words I want to disconnect the HVAC system to see if this is the cause of the fault.

I found manuals online which are good, except i can't seem to find a clear description of where some of the connectors are to do further IR tests on. I did do the HV connectors on the charger behind the back seat and they check out fine.

Thanks again,
charles


----------



## Tremelune (Dec 8, 2009)

I would post here:






My Nissan Leaf Forum - Index page







www.mynissanleaf.com





Though most is normal owners, there are some people with serious knowledge of Leafs over there.


----------



## cgalpin (Dec 5, 2012)

Good point. I’ll post there this evening, thanks


----------



## kennybobby (Aug 10, 2012)

Be sure to check the ground fault/isolation sensor in the LBC before reassembly of the pack.

the myleaf forum is very non-technical in my experience. Dala (the Great) would be the most knowledgeable person on leaf packs.


----------



## Dala (Jan 10, 2018)

kennybobby summoned me!

So the thing about these packs is that they are quite bad at telling you what is wrong when it comes to insulation resistance. It can be typical to start seeing these codes on really old packs that have below 50% State-of-Health. Since your pack is still very healthy, and the voltages look fine, I'd start looking into these things.

Battery pack heaters. Are they rubbing on the modules? Try to unbolt them, and lift them up/away from the modules and bolt them back in. There has been reports of some heater pads making unwanted contact with the modules, and since these run on HV, it might affect the insulation.
Moisture. Did you notice any water in the pack? The Nissan Leaf battery pack is not that well insulated, and can allow for water to collect on the bottom of the pack. This has also been known to causing fault codes. Simply opening the pack, drying it out and re-installing it helps.

This usually starts to manifest itself when quickcharging. If the error hasn't occured when quickcharging, it is a bit strange that it all of a sudden started to do this on L1/L2 ...


----------



## cgalpin (Dec 5, 2012)

The more the merrier!

@Dala, moisture was the first thing I suspected given the outside of the battery box is rusty, but it was bone dry inside. I have now removed all the heaters so can't look, but it's possible there was some unwanted contact there. I did notice some warping in the plastic - perhaps that is a sign? When I reassemble I'll try pay extra attention to those. This car doesn't have chademo, but in under 1 minute of charging it threw the code.

@kennybobby, can you tell me how you test the ground fault/isolation sensor in the LBC? I have been using the manuals from nicoclub.com but don't see anything that detailed. It just explains you can't swap one out without programming, which rules that out as a quick test method. I'm no EE but this looks good to me - what does this look like to you?


----------



## kennybobby (Aug 10, 2012)

i haven't traced it out, but that board would be easy to trace since all the component reference desigators are silk screened.

But here is my guess on what may be on that board: i think that relay may be involved in the IR measurement circuit. The top of the HV is divided down by that R804-R808 resistor string and connected to the bottom of the lowest cell when the relay closes. This generates a reference voltage that is compared with an average of the sum of the cell voltages. If these two don't compare within an expected range then it is assumed that the difference is due to current leakage of the insulation.

i would replace the relay as the contacts may have been frosted by intermittent switching due to the low 12V aux battery.


----------



## cgalpin (Dec 5, 2012)

You mean this b3ga4.5z relay? Ugh. Is there a way to test it in place?



https://www.mouser.com/ProductDetail/Fujitsu/FTR-B3GA45Z?qs=eo0gZC5IfqM6nhnVSG92Vw%3D%3D&gclid=CjwKCAjwzIH7BRAbEiwAoDxxTmhN0y2seFbmaPGHH9WFnXKa4oPdVsB-rerp9nIn7_jpshDhaI3gRRoCk3IQAvD_BwE


----------



## kennybobby (Aug 10, 2012)

It's just my thoughts to go ahead and replace expendable or wear items as long as you are in there, but it is really only my guess about the circuit. i didn't see any scorched or damaged areas on either side from looking at your pictures. The software controls the car so if you don't find and fix the issue, then it will likely not operate. Do any of the electrolytic capacitors appear to have swollen tops?

If there were a schematic then you could do some troubleshooting, but i have not seen one. i don't have a spare LBC or i would have traced it out and drawn a schematic for you.


----------



## cgalpin (Dec 5, 2012)

Yes, sorry if I sound ungrateful - i am very grateful for the assistance. 

I guess I have nothing to lose but time (and this is taking the wife's parking spot in there garage so at some point I'll need to concede defeat if I don't get it working before the winter).

The caps all look good.


----------



## cgalpin (Dec 5, 2012)

Sadly that didn't work. I replaced the relay (i won't win any awards but I believe I did it correctly), but the symptoms are exactly the same. I never got around to posting on mynissanleaf, and will give that a try, but I think at this point I'm just going to keep the battery and part out the rest if I can't find the cause outside of the battery (like in the HVAC system).

Thanks a lot for helping.


----------



## kennybobby (Aug 10, 2012)

If you want to send me that LBC board, i could trace it out and send it back--might help the next guy.


----------



## Dala (Jan 10, 2018)

I have access to a "Fix" for dealing with the finicky leaf batteries that I have never used yet. It is possible to overwrite the LB_IRSEN with the use of a CAN-bridge hooked up to EV-CAN. This eliminates any IR-errors, but you have to be damn sure that your battery actually isn't defective if you want to use it.


----------



## cgalpin (Dec 5, 2012)

@kennybobby I'll likely take you up on that offer. Would be great if it could help someone else.

@Dala I understand, but since I don't plan to keep/drive the car I don't think it's worth it. When I was plugging in the low voltage connector to the battery this weekend, i thought of you. If i get time, I'll design a 21 pin gen 1 connector and 3d print and test it before contributing it to Nissan-Leaf-Battery-to-OBD2.


----------



## dbertolet (Dec 28, 2020)

I'm having the same problem with my 2011, which had its main battery replaced in 2016 by a dealer.

One thing that caught my eye is the 12V putting out 7.5 amps. Mine also shows 7 amps, but that seems high for a car that's only powering a dash display (no other accessories on). I'm a newbie though, so can anyone chime in about that current level?

So... can anyone point me to good DIY documentation on tracking down ground faults? 

cgalpin, did you ever figure out how to fix yours?

Thanks everyone!


----------



## cgalpin (Dec 5, 2012)

I had not noticed that, but I am not sure what it means. If you are trying to keep the car, buying a new 12v battery wouldn’t be a bad idea to try. I pmd you the link to the manual which explains how to do the IR testing

what does leaf spy say about the health of your battery?


----------



## kennybobby (Aug 10, 2012)

@dbertolet, find the drain on the 12V system first, then you can pursue the IR issue, but i would guess that it will go away once you solve the 12V aux battery problem.

@cgalpin, i would like to trace out the LBC board, will send you a PM with contact info.


----------



## cgalpin (Dec 5, 2012)

I had not noticed the high current on mine. Could it be the dc to dc convertor trying to charge the 12v battery instead of it being a draw? A quick test is to try a good known battery.


----------



## kennybobby (Aug 10, 2012)

i have traced the power supplies and what appears to be the insulation resistance circuitry, so i have some schematic available, although i can't say that i understand how it is intended to work.

i will start a new thread to focus on the LBC details and information, and the troubleshooting and repair activities can use this or another dedicated thread.


----------

