Nissan Leaf Modules damaging Orion BMS [SOLVED]

[ekohn04]

Hi everyone, I have an Orion BMS 2 connected to a 62kwh leaf pack. I have blown fuses on the same cell on two Orions already, and am having issues on the same cell with my current one at the moment. I had purchased my previous two BMS from eBay under the same seller, and they were special ordered from Ewert with limited options. I would notice for a short time while driving that cell #33 would have a very high resistance (12.7 vs the .3 average) and then some time after the fuse would blow on that cell. I purchased a different BMS for my third try to rule out an issue with that specific configured BMS. It is now showing high resistance on that cell. I have completely redone the wire that goes to that cell tap, and as it’s at the end of my cell group I was able to replace the spade terminal I’m using and can ensure the connection isn’t loose. I keep seeing this pattern of normal operation for a couple weeks, then all of a sudden the one cell has an issue. Can anyone think of what the problem might be? Thanks.

[arber333]

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I keep seeing this pattern of normal operation for a couple weeks, then all of a sudden the one cell has an issue. Can anyone think of what the problem might be? Thanks.

I saw on multiple occasions how another cell positive side would pull dirt into unprotected cable strands.
That means cable starts to corrode and i guess resistance goes way up.
Do you use bare copper in your tap wires? I would suggest replacing them with tinned wires.

Also what would be more distressing... could you have a problem with DCHV touching chassis ground? Try to connect incandesent light bulb to chassis ground and HV minus. If the bulb stays lit you may have a problem.

[ekohn04]

Try to connect incandesent light bulb to chassis ground and HV minus.

That's a handy trick! Unfortunately (fortunately) the lightbulb did not light.

Do you use bare copper in your tap wires? I would suggest replacing them with tinned wires.

I have been using bare copper wire, but I doubt this is the root of the issue. The wires have no corrosion upon visual inspection, measure 0ohms with a multimeter, and when driving with this issue the internal resistance values vary wildly. Sometimes they start out as normal, then shoot up to 20, down to .5, up to 9, and so on. After cleaning the terminals today to ensure corrosion wasn't the issue, driving the car resulted in the fuse being blown on my third BMS (I disconnected the cell tap connectors before cleaning the terminals). I'm frustrated because these things aren't cheap. If you or anyone else has any ideas on what I could do to diagnose this issue please let me know. Thanks for your response.

[arber333]

That's a handy trick! Unfortunately (fortunately) the lightbulb did not light.
....

OK... this just means HV- and GND are on the same level. Now connect one side of the bulb to that culprit cell positive pole and chassis GND.
Edit: just so that we understand each other. The light bulb needs to be AC rated incandesent type. NOT 12V.
Or you could wire two of them inline for higher resistance - lower current.

It shouldnt light up. If it only blinks then your inverter caps discharged. But if you have a path to GND bulb will light continuously.

I have seen this happen because of shady water heaters and bad welding. Surprisingly bulb would get its connection through coolant! If i removed coolant there would be no more problem...

Another thing... did you consider your BMS wiring is not correctly assembled? Would you try recrimping that and some neighbouring connectors...? Sometimes those small wires break on crimps...

[jrbe]

Consider wearing high voltage gloves doing these tests. If something unexpected is wrong it could get very ugly.

[ekohn04]

Thank you both for your responses. I religiously wear high voltage gloves in these situations after an instance of naked fingers in the HVJB.

It shouldnt light up. If it only blinks then your inverter caps discharged.

Using an AC incandescent bulb, I did tests with all the polarity/cell locations possible. The biggest thing to note was a very small spark that would appear when I connected the lightbulb to the wire I was using, but no light from the lightbulb. The lightbulb was confirmed working before and after the tests.

Another thing... did you consider your BMS wiring is not correctly assembled?

I did consider this, and decided to completely rewire the harness that contained the cell in question. I replaced the Orion connector with a new connector and all 36 wires that go to the cell taps with tinned wires. It didn't fix the issue. The only accessible thing that I didn't replace was the Nissan connector that brings the cell taps out of the module. Here it is pictured.

The last thing I can think to do is bypass this connector on the neighboring cell tap to the cell in question (the cell in question is tapped by a physical spade connector that I have previously replaced). I will bypass the neighboring cell tap with a solid wire and see if that fixes the issue, but I doubt the factory Nissan-crimped connectors are the culprit. Any other ideas?

[anthonyevs]

Ive seen in the past Dala had an issue with his 62kwh leaf battery with HV isolation on a cell in the rear stack. That cell group was damaged and leaking hv voltage thro the battery case.
He had to remove that stack and replace it with a used stack from a seperate battery.

Just a thought
Anthony.

[ekohn04]

Thank you for your reply. I think I've found the issue.

I decided the module itself needed a visual inspection. I removed the front cover:

When trying to remove the black plastic piece at the top of the upper image, I noticed something. The left terminal is clipped onto the black plastic piece, and when I pulled the plastic away from the module, the area where the terminal was welded onto the cell stack pulled off.

This is most likely what has been causing the intermittent connection issue. I have a traction wire attached to that terminal that was pulling away from the module, and the vibration of the car coupled with this pulling makes a strong case for it being the culprit. I'm going to post in the Nissan section for any ideas on how to fix this connection. Thank you everyone!