I plugged in the balance lead with reversed polarity….twice. 
Repaired burned trace, swapped out new jst connector and burned pin.
Bms was wrapped in fish paper and kapton. I assumed the polarity of balance leads was like 90% of the other bms’s I have encountered. I was mistaken.
Lesson learned:
Verify bms input labels on the actual pcb markings.
So frustrating. 
Glad you got it worked out though!
I forgot how much of a pain it is so weld Molicel cans. 
I hear people talking about this all the time, but I’ve never had an issue with it. What’s the rub?
1/10 cells just doesn’t stick, I can get good connections at 50J on 0.2mm for most of the cells but every now and then there’s a few that just don’t stick, I can dent the can and vaporize the nickel but still nothing
What welder do you use?
Is it super obvious that it doesn’t stick?
Well it just falls off when I do the first tack
Perhaps you’re pressing too hard? I think I remember @A13XR3 saying something about how spot welding exploits the gap between conductors to spike the resistance and make the weld. If you press too hard there’s no gap, and therefore very little resistance. But 
Very likely, spotwelding physics needs resistance to perform the weld. You push down too hard and eliminate the air gap, your resistance decreases, weaker weld. Light but firm touch is the key.
Hmm it seems I missed the sweet spot then
54J for me, haven’t had this issue in the past on my kweld
How pointy are your tips?
Damn son, you need to sharpen dem tips
Really? Mine look like that too, and they weld fine.
I used to weld with tips like that with minimal issue, but the welds seem to go down better and more consistently with sharper tips
I get mine about as sharp as a marker, and it’s good for about 20 cells before they need a cleaning
Although the J system is supposed to eliminate it, I find my kweld still is very sensitive to what batteries I use.
The standard setup i have is 2 parallel 6Ah 75c Graphene lipos. 36-38J and it’ll weld .2 perfectly. Its nearly double that when im using an older car battery…
Yeah 54J for my 6000mah turnigy graphene. Could be different for other batteries.
