timselectric
If I can do it, you can do it.
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Maybe the BMS wire crimp is loose.
Jk BMS shut down and unable to restart
- Thread starter fx99
- Start date
I never liked rigid bus bars even the ones with bends in the middle, I think they are still rigid. I also don't like compression, in my assembly I put 0.08" thick rubberized sheets in between the cells and also side plates. The threaded rods are just to keep them together.
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But how, I don't see how it wouldn't have been solved by previous testing. all bms connections were renewed, the one at cell #6 was tested so many times. and if it was a connection issue, then why wasn't it there from the beginning? ?
timselectric
If I can do it, you can do it.
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Loose crimp will be an intermittent connection integrity. Pull gently on the wire and see if it moves in and out.
wow that's a really clean setup ?
I also mainly compressed the cells for stability. I put a sheet of packaging foam in the box and pressed it together against the cell walls with one of the side boards that make up the wooden box. Compressing the foam took a bit more force than I thought, but I would say it's probably still below the combines 600kg for two cell walls. hard to say for sure though, obviously screws can quickly build up alot of force with little effort.
Between each cell there's a 1mm rubbery sealing plate (Tenasil NG) to prevent a short between the cells.
After compression I installed the bus bars, they are pretty flexible but obviously no where as much as the cables you used.
But in general I think my setup should still be on the safer side, compared to all the ones with rigid busbars and a metric ton of compression ?
You are right of course but in my case that would mean that I somehow managed to badly crimp the wire for only cell number 6 twice, even though I used expensive crimps, high quality pliers and checked each crimp before the installation ?
Edit: and I have switched the problematic cable at the plug and the cell with another cable but the warning didn't move with the cable
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timselectric
If I can do it, you can do it.
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Ghost gremlin lol
@fx99
This is just my guess. It seems that the terminals of the cells are made of 3 separate pieces, the bolts, the flange (B in the picture) and a round stud (A in the picture).
If the BMS again reports an anomaly, use your DMM and measure if there is a voltage drop between A and B and C of the suspect cell. It is possible that there is a manufacturing fault between A and B that appears intermittently. This is assuming that A and B are separate pieces, the picture is not very clear.
Your setup is nicer.I also mainly compressed the cells for stability. I put a sheet of packaging foam in the box and pressed it together against the cell walls with one of the side boards that make up the wooden box. Compressing the foam took a bit more force than I thought, but I would say it's probably still below the combines 600kg for two cell walls. hard to say for sure though, obviously screws can quickly build up alot of force with little effort.
Between each cell there's a 1mm rubbery sealing plate (Tenasil NG) to prevent a short between the cells.
After compression I installed the bus bars, they are pretty flexible but obviously no where as much as the cables you used.
But in general I think my setup should still be on the safer side, compared to all the ones with rigid busbars and a metric ton of compression ?
This is just my guess. It seems that the terminals of the cells are made of 3 separate pieces, the bolts, the flange (B in the picture) and a round stud (A in the picture).
If the BMS again reports an anomaly, use your DMM and measure if there is a voltage drop between A and B and C of the suspect cell. It is possible that there is a manufacturing fault between A and B that appears intermittently. This is assuming that A and B are separate pieces, the picture is not very clear.
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I knew it ?
Of all the crimped wires sizes that are problematic for me was the 22/18. I refuse to even try to use the insulated crimper, even with a Kline it’s been poor. I remove the heat shrink and expose the barrel. I fold the wire so the bend just comes through and crimp with an MC4 crimper that the jaw’s small position has been oriented for maximum force close to the hinge. Then a quick wetting of 40/60 solder just to plug the spot where the wire bend is because the new shrink tube can’t quite seal that spot. Now it’s bulletproof with a strain relief. Why so meticulous? Because I’ve been there and never going back.
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I doubt there’s a problem with post to mount weld. I’ve seen the result of a drop test.
Those welds, thou they may look like a superficial low penetration laser, they have me impressed. An internal resistance meter around the flange and to the post showed no signs of a fracture . The post inside the cell is actually what bent. Yes the internal resistance and voltage was exactly the same as other cells. And, No way am I using them. Seller replaced immediately. I highly recommend a quick buff with 3M cloth on the mount surface and the bottom of the flexible buss bars. Use antioxidant on the contact surfaces.
damn that sounds excessive but you are probably right. won't have to worry about that again ?
but was that general advice or do you also think my crimps are the problem? I'm so sure that they are good after all the testing ?
When problems go away and I’m not sure why, just gets me more concerned. Can It happen again?
wow that's insane. good to know that I probably won't have to worry about them ?
I did buff them and clean them with Isopropanol. Used antioxidant ("Wago Alu-Plus", basically the same as Noalox) as well ?
good thought, but I would have noticed that during cleaning for sure
yeah I'm not happy with the situation either ?
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