Hi! Electrician here : Your high voltage gloves MUST BE WORN WITH LEATHER PROTECTORS over the insulating layer. They are NOT designed to be used without leathers!

Hi Dala. Just a thought. I used to work at a Nissan Dealership and we had isolation problems on 62kwh packs more than once. I was always that exact same module you are working on. Never a physical dent or damage but rather internal chemical defect that caused the leak. Under warranty we would always end up replacing the module altogether and we never had any comebacks.

I would loosen and retighten every pack, re-position all the straps , re-tighten those, inspect and reconnect all the bus bars, then test it again. I would make a cable to connect the battery to the car without installing it in the body, and test operation with the car up on blocks, use leafy spy, and test all systems...see what you have.

Well, first you need Megger (Fluke 1507 for example) and use it at 500V area. Then inspect that is there connection to battery chassis/frame. Because there has been collision, there can be bend module frames or battery pouch leaking electrolyte. Also find out those bad cells and replace them after knowing reason for isolation problem. Do not make same mistakes what I have done with my Focus Electric. 😁 - Measure first with Megger, normal multimeter is quite useless with inside battery repairs. - Take videos to yourself to remember measured values and you see your working methods, are they have been right in the past (like if you do wrong diagnose, you can double check). And be happy that you do not have coolant cooled battery as I have, also you have more space and warm place to work, I did not. This is quite simple diagnostics after all. When you start figure out Megger and circuits in battery, you will find problem quite quick. Next time is so much faster and comfortable to do when you have some routine. Lycka till, lykkyä tykö! 🙃

I was late for work because of this video. Totally worth it.

A further thought. The pouch cells within a module might have shifted and one or more of the cell tabs come into contact with the cell case. Removing the restraint bars may then have alowed the bent cell tabs to push the pouch back into place.

When you have torqued the cell, you did not have the angle iron bar as part of the configuration. I noted there was one when the cell was in the pack. Maybe this difference in load in the pack is enough to not induce the fault. Try re-torquing with all the hardware as it would have been in the battery pack, and see how that goes. I'd not be trusting the pack as it is tho.

So impressive to see people that understand electronics.

Thanks for the video. Very interesting stuff. I'm sure you will figure it all out.

The dent does not look high enough to touch the battery. Loosening the connection terminals may have changed the contact resistance. Try loosening the plate bolts, take a volt meter measurement then re-tighten. Try this method with a meter continuously taking readings. Maybe just a bad contact.

I'm never going to take my battery out however this is enormously interesting Dal. Thank you for sharing.

Hi, Dala ! Given the Voltages in the video (-22,43V and 12,58V), it is easy to say, that the problem comes form some of 3rd cell row in the pac (form top, or from the bottom - I don't exactly know, should check that on the module itself, having in mind that pac comes with 9s2p). Lucky for know that it is probably only one cell to ground for now. If there would be a second one too espiacialy in some longer away pac there would be high currents floating between with fire in the battery. The idea that battery was in car crash and because of that some screws moved is not necessarily the truth. Cells in those pacs are very well known for being often expanding with aging and especialy QC to full in hot environment. If that is the case, if all cells are expanding the pressure could even move or even bend the screws. But of course - that is the sign of seriously used battery. Would be easier to check live with a naked eye if that could be the cause because it is hard to say from the video

what I like in your video is that you are very safe when working on the high voltage system you have proper PPE and isolated tools etc to work on this I see a lot of videos on U tube and they don't take it seriously and hope that you find the problem and you fix your car cheap.

Greetings from Sweden. Since i am just in my first month of owning a 2019 40kW Leaf @ just 38000km. I am watching your videos to have the knowledge when there will be a problem. I thank you for your great work. I am looking forward to the upgraded charging projekt.

Great video and thanks for sharing. Can"t add much more than what has been suggested below. You do need to find the reason for the lower voltage cells though. Check connections that may have been loosened in the accident. Good luck !

Thanks to let us look inside!

Extracted module is in 9s configuration. Looks like one of the series cells is leaking to its outer casing. Compressing doesn’t work, probably because it was touching the battery case when it was inside. I guess you’ll have to carefully examine the module for visible damage, and also take some voltage measurements around. Problematic cell should be #3 from the top or bottom.

To my mind that dent was superficial/cosmetic and very unlikely to be connected with your stack short. Much more likely is the possibility of an internal short to the case which has disappeared when the stack was allowed to expand free of bolt pressure. You need to look at the internals of this stack for the possibility of a short around the centre part of the cell stack. Very informative and educational videos - I commend you for them.

Hi Dala, I would add to dissasembly all other stacks to correct bendings from the crash. Also, after complete the pack reassembly, performing the insulation test with Megger in the extreme temperatures you could have in the future. Best regards

Flattening the dent from below might be the solution to removing any additional compression that caused the ground. Or lay a thin sheet of insulation between the case and the bottom of the stack, and re-assemble to test. Possibly a thin sheet on top if it's closer to lid, but when re-gluing it you could also put a thin shim along that side of the lid before bolting it down to gain a few millimeters of clearance if needed.

Since the same area seems to have a problem in other cars I would swap the cell pack to the right or left if possible and hope I get lucky for a while. Great work! it's likely too late but I thought I'd add my 2 cents.

Seems like pretty good news. I'd be pushing hard on the bottom of that module where the dent was to see if I can get the earth fault to come back. If you can't, then put it all back together (checking for the fault along the way) and hope you have a reliable battery pack. I'm also a little concerned about what caused the other cells to discharge like that. I'd consider pulling them out and inspecting them closely.

Is there a torque level that you have to reach when re-compressing the module? - What I am thinking is that you might not have compressed back the module at the same torque level as it was while inside the battery. - So maybe if you compress to the adequate level, you'll see the problem coming back. - If you do that test, then you can have bit less of a chance to get the problem re-occurring when you put it back all together. - You are one courageous man!

I would have to say that something likely shifted when you took the compression bolts out, and personally I would not trust this stack to be reliable long term unless you can tell for sure what shifted and that it can be repositioned where it belongs. For my own curiosity I would next use a megger to check the stack to chassis, if something is really close to touching you will find it with that. In the railway industry we use Hi Pot testers to find defects like this in the high voltage traction circuit but that may be overkill for this😂Can't wait to hear the follow up and thanks as always for an informative video :)

Hello Dalla, good work you found the module but it must be one of the pouches inside of the module so you must disassemble that module and inspect each pouches it seems that mr coutiernicho knows so just replace it and use that battery again in your car

Hi Dala, we are doing repacks with modules from China and one of the modules was placed on an uncleaned surface. It has a small dent of 2x3mm and is less than 1mm deep. This module is shorting to ground due to the one cell being damaged. The modules are made up of prismatic cells stacked upright and bound together. Technically speaking, when the cells are manufactured, the insulator that is rolled up with the active material should overlap a little, so that when the flattened roll is squeezed into the box, the active material should be nowhere near the metal can housing. Clearly these tolerances are way lower than we would have though, or we were just very unlucky. In your case the dent that was made in the base of the pack, clearly pushed fairly hard through the steel 'frame' of the module and made a dent internally. You would have to bolt it back onto the bump to replicate the fault again. My advice would be to replace that module/cell if at all possible. The chances that this cell will fail prematurely are very high, as dendrites would have a much shorter path. The soup packet cells seems are more forgiving, so if you wanted to take a chance, it should be ok to remove the dent and refit the pack. Thanks for putting your stuff out for others to learn from. Great channel!❤ Regards Jens

At what point did you disconnect the BMS harness from that module? Was it just before removing the compression bolts? It's possible the isolation problem has to do with the BMS or BMS wiring.

Nothing better to say than Nicolas Cloutier. Anyway, disassemble the pack and check each cell. As said Nico, internal leak seems the more possible reason or maybe a cell damaged. The leak shoud be reproductible. Can't say better because not in front of the pack. Congratulation, you are back on track to solve this problem.

great content

If it has been involved in an accident at some point that compression point is the number one suspect on it all. It could be as simple as a small segement touched down internally and when you released and moved it the fault point moved enough to not come back under compression. Given the amount of work to remove and refit I'd just throw a replacement stack at it and realign all the bolts and the like back again.

Great video, I can’t wait to see the root cause. The person that worked at a dealership seems to have the best advise. Determine their cell and replace it. Or is the BMS damaged?

Good video and information! I'm waiting for a final conclusion. My 40 kwh battery haves the same error, since June 2022. I still drive the car, a 2019 Leaf, erasing the error each time I start it. I made 8000 km since broken down. The condition of the battery has not worsened during all this time, but the SOH has decreased a little, with 2%, which is quite normal, in 9 months. The strange thing is, it's a single station in my whole town, that let me charge it to 100% with no error, other ones stop charging at 30-35% SOC, when the error comes on the dashboard. Under 30% SOC, there's no error on dashboard, never. It works completely normal, heather and AC as well.

Hi Dala. Thank you for sharing. Have you checked the isolated busbars of this module for breaks on the insulation? I know this is a simple thought, but you never know.

The voltmeter measures against a high resistance load, (the internal voltmeter resistance is very high). It would yeild more information if you can adjust the load that you are measuring the voltage drop across. So put a variable resistance of some sort in the path and measure the voltage drop across that. Provided your resistor is rated high enough wattage. I'm thinking internal damage to the cells (internal resistance of the battery coming in to play) will have a different characteristic to an insulation problem.

The fact you were seeing 12/24v suggests that there is a short or leak one-third of the way through the series stack. It would probably be useful to measure the resistance of the short by seeing how the leakage voltage changes if you load the meter - that should show if it's a dead short or resistive - e.g. moisture etc. I suppose x-raying the pack might show up internal damage, but probably needs a powerful industrial x-ray to penetrate the steel sufficiently.

Seems like a tricky situation. A weak module that you charge to balance, if weak will eventually imbalance itself again. I remember some other Leaf owners mentioned something about testing the modules under heavy load. Essentially "weak" cells would drastically drop in voltage when flooring the accelerator. A bit tricky to "replicate" that load but it's something to test and verify if your weak cell will end up losing balance again. And the worst is a weak cell shorting and frying the rest of the pack like mine did. As for the shorting pack... I'd personally replace it. I guess tldr, replace both modules. These should be specially manufactured so I don't think they disassemble as easily as the 40kwh modules. You could try out of curiosity and see if you can repair it but my gut tells me the high density leaves it more vulnerable to physical damage and as you said, these are damaged. If you have an isolation issue once, you'll get it again. Also to properly replicate the isolation, you would actually need a bottom plate to mount it to right? I don't think the bolts are enough as the shell flexes. Either ways, you don't want to be surprised by an issue you didn't fix with certainty while on the road in a 3500lb moving vehicle.

Still worth what you paid , hope you get it sorted out .🇬🇧

Top Man!

Since you are getting negative leakage voltages then that implies a positive from a cell somewhere in the middle of that pack is not right. Can you pull the pouch cells out one at a time and inspect the ones around the middle?

Hi Dala, one of the pouch cells of the individual battery packs may have become defective due to the mechanical stress of an accident, this may only have an effect when the entire pack is pressed. Perhaps use an insulation tester (approx. 1000 volts) to carry out an insulation test on several cells in the block in question.

Can you dismantle that block and lay it our into individual cells and then examine them carefully. If any electrolyte has leaked from any block or bank of cells id scrap them off. If the individual cells look ok when dismantled and they are not electrically leaking, then id put them back together, bolt the case up, and install it back in the car and run it for a few hundred / a thousand km and re assess. AT the end of thet day you have nothing to loose at this point. Great video, and good luck with it.

Could it be related to a torsion issue? By that I mean, when you bolt the battery back into the base it could be twisting the cell casing slightly. It twists just enough that driving vibrations start to shift the internal pouch cells by micrometers, causing it to either wear away or permeate the isolation material and contact the outer casing? It’s just a thought.

Maybe you need to take a very close look at white “insulation” in pack - are there any small holes? Can you add another layer near shifted cell stack? Any loose pieces of metal in tray?

Great diagnosis and I think because that looks like it jolted the pack and the dent was under that module and that's the one you had the leak on, I wonder if it internally damaged one of the cells and it is one of those that's given the reading and you uncompressing it and then recompressing it helped it for now. I would fear that once the cells have heated up and cooled down under charging or driving you may well see same fault again. I know you said they hard to get hold of but for piece of mind I would keep a eye out for a replacement module, but getting one to match age and state of health will be a pain. I guess you could also strip down the individual cells and see if any obvious signs but maybe shock of crash internally damaged a cell. I also guess if you don't mind having to re seal it and then maybe having to drop it again you could refit and test.

I would reinstall the battery cells and hook everything up to the car to see if anything has changed. I can't tell you how many issues Ive resolved over the years doing nothing but investigating the problem. It could have been an unsecured or loose connection that you fixed by removing and reinstalling. Too bad there aren't battery extension cords for your car :)

nice videos my friend, you really add value to the community. quick question, is it possible to remove the top speed limiter on newer leafs? the 62kwh version is capped at 165kmh can that be removed? also, would it be bad for the battery/motor? would be interesting to know!

Your channel is amazing , i had alot of knowledge about ev batteies, can you explain what is the isolation problem ?

Slacken everything off re align everything tighten everything back up and see how it goes

I think the first thing will be reproduce the leak.. put it where it was, (no dent repaired) screw it down and check if you have a torque wrench, check how much do you need to tight the battery to start measuring something... if you manage to reproduce it, then you can extract it, and put the battery on top of a metal plate with a nut/ screw (small one) underneath... that way you are replicating the conditions outside the battery pack... if you see the problem, then the problem is 100% identified... then you can dig a bit more... disasambling the battery and checking for damage on each cell, or you can think in solving the problem... you can replace the module or just simple flat the spot, then put some soft foam isolation (just a bit more, just in case).. then close the pack and enjoy as it is... (of course if you can replace it together with the front cell that is damaged would be perfect... but if you dont find a replacement, then just enjoy what you have

I guess most of us will be keen to know if there are any simple tests to check a battery pack before buying. For example, would a resistance/isolation check between HV connector pins and the case show us a leaky pack or do we need the pack to be installed in a car with contactors "on".

Since the cells are super low resistance, i would think it would be safe to use a Mega-ohmmeter (Megger) to see if it can locate the weak spot. It works wonders for mains wiring.

Since there was this dent in the bottom right under this cell, there might have been some pressure from the underside of the cell. To emulate this pressure a C-clamp might be used. Have a thick steel plate at the top of the cell in order to spread the pressure at the top of the cell. Then place the C-clamp approximately at the place of the dent and squeeze. Another possibility is the misplacement of the cell. Maybe they did not loosen the attaching bolts for good lookibg cells and only replaced the bad ones or none after the crash. When You loosened the cells, the cell frame straightened and now there is no more leak.

Measure isolation with high voltage tester. The cells will have an isolation spec. It might be VERY HIGH, I would not be surprised if it were >3,000 volts ac or > 4,500V dc. If that seems high, bear in mind something like a metal cased Sky+ set-top PVR box is tested to 3,000V ac for 1 minute

Need put back to main battery place and measure again. And I would use vacuum to clean some extra dust. Industrial dust always present. Thanks.

Was there anything else beyond the compression bolts that's missing to try recreate the issue here

Nice work. from my point of view you should probabky take out a modules, inspect them for damage and reassemble. Replace bent parts and maybe use new fasteners. If the problem does not reappear you should probably be good for now. if the cells had been damaged, they would most likely have caught on fire by now, but the shifted positioning and so might lead to issues with chafing insulation, so better review and reposition. If you can stresstest the module outside the car and fully charge and discarge a time or two before putting it back intt the car. Hopefully then you have a working and reliable pack again. If you want to play it more safe, then you would need to dissassemble the modules and check every cell.

I think a cell tab in the module has been in contact with the housing. I would open this module, to see that all cell tabs are located correctly. maybe it's only 0.1mm between tab and housing now. Then a temperature change can cause it to come into contact with the housing again, and the same problem occurs. Then I would loosen everything in the battery pack, so you can put everything back correctly. After that, I'm sure you can use the battery without any worries. The cells in the battery can actually withstand major mechanical damage and still function perfectly well. If you stick a screwdriver through a cell, it doesn't catch fire, it just grinds and smokes a bit, but the cell still works. Having said that, you should never use a cell that leaks. But the cells in the Leaf are among the safest used in any electric car. How often have you heard about a battery fire in a Nissan Leaf?

The voltages you measured between ground and battery terminals before you removed the faulty module were 12.x and 24.x. This suggests the short happens on cell number 3. I suspect that cell is somehow shorted to the one of the compression bolts.

I saw such damage - the cell was touching the screw. There should be marks on the cell and the screw. Just put insulation on the compression screw.

Dala, can you help finding the spec on a 40Kwh battery? I have the same issue internal battery pack insulation leak. I am not able to find a vedio or spec on it. Thank you

I would take apart that module and examine the pouch cells carefully, and measure voltages before reassembling the whole pack. I don't think that dent had anything to do with this. The hard collision has compromised the internal structure of one of the cells. Good luck!

If I was you , I should taking apart the hole damage cell part and inspect any damages!! do not put this pack back with the rest of them!! try to buy an other. you may damage the hole pack in the future or take a fire after some chademo dc charging. Also try to find the isolation issues with a megohm-meter, so buy one!! when we make inspection or an isolation issue , there is only one type of meter that send 250V 500V and 1000V dc to the line in order to find the isolation issue, megohm-meter . You will never find isolation issues with a simple Ohm meter only... the pack was squeezed but also was under a big voltage ! the issue is there and for the most part must be from the half of the pack and down!!

Did you get a warranty on the battery pack

@DalasEVRepair I have this problem on my Nissan Note e-power HE12. I am very sad that the megohmmeter and other measuring devices cannot detect this problem... leaks and startup prohibition - while the problem is “floating”, you can drive 300 km, or 50 km... and then get an error...

ballance all cells, check for continuity, before closing the battery, i think the whole battery pack is ok, the drop in the voltage on 4 cells must be because of the leakage, double and triple check for leakage before closing the battery.

Is it possible to investigate the accident that the battery pack was involved with? I'm assuming the pack was tied with a VIN number - does Finland have a national database of insurance write-offs? Might give us more of a clue as to what actually happened. - Nikki.

If pack did not have isolation problem, would BMS charge up that module that was 30 mV lower than others?

I think of a problem of insulation in the holes where the bolts pass to put lock the battery. I would try to isolate these bolts

just put everything together and the modules directly. what else can you try?😅

Hi. You should test condition of the next module(to the left from this one). The point of insulation will be with no voltage to body, but with low resistance.

From the voltages it looks like short circuit connection to ground somewhere in the 2/3 or 1/3 fo serial string of cell. You cen exactly count which of serially connected cells in module was leaking from the voltage of cells and the leakage voltage. I expect it will be somewhere in the middle. Dent on the bottom could have nothing to do with the issue. Locate the cell and you will see what is bad. Are the side walls or the area where are cells connected each to other ok? May be the module was shifted from the forces from accident and something touched the metal cover from inside. I am just guessing that in front there are 7S, middle is 4s and rear are 9s configuration so it should be short circuit between connection 3rd and 4rd cell to the ground. Good luck!

Hi i would leave module tighten like this and charge it up to the max level than discharge if thermal expansion will return the isolation fault if not i would put it back

Grub megaommeter and see what is said. This is how I pinpointed some insulation fault on defective 40 kWh pack. But my case was been much more obvious.

I think that the compression was at the place of the deformation of the sheet. But when you tighten the 4 nuts, the compression load is not at the point of impact on the sheet.

The Rods are steel, if some cell is little bit unpricise, it can give voltage to the rod. Once One Ukranian disasembled the pack with the same problem. He just covered up the Rods with isolation tube and the problem was gone. It was 40kW pack. This problem was not in 24kW packs.

Replace that module, for peace of mind. Also check all of the base of the pack for more dents.

Sorry to hear about the bad news Dala, one question though, did you get the pack from Norway, and how does the seller react to the situation? Will they refund you, at least partially? And would you then get back the import tax in Finland (for the difference?)

I think the crash was too violent and it may have affected some of the cells in that module(marked X). I would also do a thorough check on the module that has lower voltage because is very rare for these batteries to just go off balance. All the best.

Does the fact it was 12v to ground from one terminal, and 24v from the other give you a pointer to where in the cell pack the ground fault is/was?

The cell was being crushed in the centre from below. Hammering out the dent will remove the crushing force so it will probably be OK but has the cell been irreparably damaged? Clearly it was not a serious safety issue as it was only 12V to ground so safety is not a concern here. Only you know if it is worth trying it again with this cell as it is your time you will be wasting should it fail again. How much are replacement cells (if available) How much is your time worth?

May be the dent was putting pressure on the module unbolting it relieved the pressure

I don't think crash damage is the cause, rather a coincidence. Disassemble, assemble, torque properly. If no physical leak, replacement is not mandatory.

The LoZ mode on your meter should work faster for the measurement because it introduces a bit of load to the circuit and discharges the capacitor quickly?

Further disassemble the stack where the fault was, if that dent has in any way pushed onto the pouches inside you might be able to see this on the bottom one, and that would be smart to investigate.

When working on hevy cells like that please keep them on a trolley so if things go bad you can quickly get the pack outside.

I might be 10 months late now, so I hope your memory is excellent as always. Not related to the reason you took your pack apart, but I've been trying to figure out how the 62 kWh packs keep warm without a physical battery warmer for years now. When you took apart the pack, did you see anything inside that would facilitate a "software" warming mode? The hypothesis for years has been the shunts, but don't know if they can produce enough waste heat for the whole battery?

Are these out of warranty already!?

The Dent itself looks like it was made with a forklift for instance... The presumed shift/slide of the pouches in the pack could be explained by this, the pack sliding of the forklift and dropping on concrete? That's a hell of alot of G's with no deceleration distance whatsoever!

I'd knock out that dent, realign everything correctly put it back together and do a further insulation test. There doesnt appear to be anything physically or electrically wrong with the cell module itself. I'd defintely capacity test that low cell to see if it matches the others while you have the battery apart - it may need replacing.

if it was up to me i would take apart all battery modules cell by cell and inspect for any tears in the pouch cells, safety is at most important when dealing with these ev battery packs especially if it came from a crashed vehicle.

I would put some insulation strip of material under all those modules and out it back together. Should work for coming years

put it back.. and draw a 1amp load from that module and the frame .. and use a thermal camera to show where the heat is.

Please check if there are no connection between compression bolts and the modules in pack. Looks like I saw a video with damaged pack, where some of thin leafs from the modules touches that bolts.

Hi Dala! I don't understand how manually balancing the one stack would fix anything. Because I'd think that the car should do this on its own - does it not? And if voltage levels get adjusted, would it not just simply go out of whack later on because of some internal defect of the cells? What caused the imbalance in the first place? Some temporary leakage during the accident or something more permanent? As for the leak: No idea. How expensive is a replacement stack? What is the worst that could happen? unexpected shutdown? fire?

8:30 when you are measuring voltage at this point, isnt the terminal still connected to the other cell?

Battery box is bent. When you tight screws in to pack + battery box something will touch wrong place inside pack, or just it bent and cell insulation fails.

Can you do insulation test with a hipot tester like Finero.. the cells have to withstand atleast 500vac insulation test in 1 minutes

The comment from Nicholas Cloutier suggests that the sub unit is faulty and Nissan would have replaced it if this had manifested before the accident. Lacking availability of a replacement, I would personally sell off all the other sub modules to recover costs. Over time we may see if Nicholas' comments are supported elsewhere and what this means for the usability of the 62kwh pack outside of a Nissan warrantied car.

You just clamped the end plates at the corners giving point contact. Maybe use the clamp brackets to create line contact at the edges.

Put 1cm small thing under the pack. Put pack on it. Just step with your 80 kg on it and measure.