I’m glad I could borrow a FLIR camera. The negative pole of the battery is getting hot. Some work to do, to start an investigation asap.
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Usually corrosion or loose crimp / bolt.
This is a lovely instance of how useful these non contact temperature measurements are.
Wow, this is really bad.
What kind of Battery is this, and how much current are you pulling/loading ?
EVE MB31 318Ah cells. Max current was 100A. The JK-BMS is 200A. So the EEL V5 battery box must support 100A easily. I’m in discussion with the supplier how to resolve this.
I’m going to take the box apart and see if I can find anything strange which could cause the issue.
Then it seem to be “just” a bad contact on the terminal, maybe the screw was not tighten with the adequate torque…
I hope that that is the case. But checked the screw on top (which is visible) and it is tight. Could be because of the situation. I hope it is not regarding the cable size. For 200A I still believe the cables are not really tick, this can be improved in my view.
I could change the cables of course, but not sure where to get the double bold cable connector from as the JK-BMS has to bold for the connection. Also still waiting what the supplier comes back with for suggestions.
That looks like one of those flexible busbars. Either it was undersized or incorrectly installed. You said it was tight but it obviously got very hot. What does the other end look like?
Indeed, flexible busbars, correct. I’ve not dismantled the rest of the box, will be done this or tomorrow evening. Will share some results of findings.
All screws, etc are tighten with the specified nm as per instructions.
I’m looking forward to seeing what you find.
I’m running EVE LF280N cells with the JK Inverter BMS in a Shenzhen Luyuan 16s battery box. I did not use their cables, I made my own.
How did you made your own? Which cable size did you use? And in particular how did you made cable connector to the double nuts on the JK BMS?
My kit came with a copper busbar to connect the two terminals. I used 2/0 cable to connect the BMS to the Class T fuse and then to the bulkhead terminal. I had plenty of 2/0 from a prior project so that’s what i used. It could have been smaller but I prefer to use a larger cable.
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This is what I use (5mil copper plate):
Drilled one 8mm hole for the SmartShunt and two for a solid busbar with a 90° angle to the battery.
I think it was like 8 pop on Amazon. Just to give you an idea.
Edit: I have seen a similar case with a DIY box. There the orange insulation sat between the busbar and the terminal. And looking at the angle of the flexible busbar on top of the terminal. Yeah I am pretty confident that this is the case here as well.
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I have built many EEL batteries (have 3 x CCS for my home and several V5 boxes on my boats). The build quality is very good and solid. I did find though, that sometimes the bigger screws used to connect the busbars to the outside lugs can wear if too much force is applied in tightening them, making them loosen up. The screws are not RVS, so I always replace them with the ones I buy at the marine shop.
I’m sure the representatives at EelBattery are happy to send you replacement parts like a new flexible busbar between the BMS and the negative connector. Also the connector itself. They have excellent service!
Glad you found it on time, you really dodged a bullet there!
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Yep, you were right on time!
As seen on top of the (6mm?) bolt, to me is seems a bad torqued bolt or a bad contact surface connection to the battery cable isolator’s connection (outside )
A new M8 bolt would be a better substitute imho.
Also a good reminder to open up my battery and check connections I gues.
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Thanks for your feedback @ChiefSolar. Interesting solution for the busbars. Are you isolating those busbars?
In the EEL Battery box the negative goes from the JK-BMS bottom to the top left corner, frontside, of the box. Will be very difficult to make that a copper plate. There has to be some flexibility to be able to make the connection.
I guess your BMS is not installed in a box with limited space? Otherwise how/where do you fit the smartshunt in the box?
Good suggestion about the isolation between the busbar and the terminal. I don’t believe I would have mounted it like that, I would have seen and noticed that. But it is difficult to check this right now. I’m putting some more pictures below after I dismantled the box.
Thanks @KEMA I agree, the screws are not of the best quality. They feel really lightweight. Is RVS the correct quality/material to used as replacement?
Also the screw on the terminal was to short to also mount the temp sensor. If the temp sensor would have been connected on the negative terminal I would have discovered this way earlier. Time for screw replacement.
Thanks @phaseshifter for your feedback. Out of curiosity, how can you replace a 6mm bolt with 8mm? The hole in the terminal itself cannot fit the 8mm bolt, correct? Or am I missing something?
I believe the quality of the bolt can be improved as well. Want to replace them in the next setup. Need to check what is the good quality, RVS?
Thanks @HRTKD for the explanation. Do you maybe have a picture of the solution you describe? Don’t understand yet which cable you use (limited knowledge/terminology my side) and how the connection to the JK-BMS is made with the two bolts.
