Happy to hear nothing blew up 
Like @BenjaminF said, for god sake don’t put more heat into that battery! 
How exactly are you planning to do this connection? I don’t really think we’re on the same boat…
When sanding, make sure you cover up ANYTHING that’s not what you’re sanding. You don’t want that dust inside your battery… I’m sure you already know this, but make sure you clean the ends of the cells with some alcohol once you’re finished sanding 
Hello guys! I have a problem, maybe professionals have idea.
I bought a 12s6p 30q battery.
There are burned points at the end of my battery, what almost new (used total 40kms). I made a diy board and some happenings were before i realised the burnings…
One time the charge port was bad, it is also burned (shortcircuit)
Then one of my vesc dead (also shortcircuit).
The bms was discharged that time, it was 40a.
The cells still good, but i have to sure i fixed the problems, i dont want to burn it.
I changed bms to bypassed, but i will use fuses.
I made stronger the end of the battery, because the wire started to melt down.
So do you think it caused any other parts shortcircuit, or the battery construction is weak and can’t hande 40 amps. (I’d like to use it with 120a already now with bypassed bms).
What do you recommend, and how can i test it?
Thank you very much for your helps!!
10a81b3951d6780a27d13a0cf599d260|375x500
The way how that looks is as if something got in and caused it to short circuit. But that nickel looks weak. Make sure not to add a fuse to the discharge wires… only for the charge port. And lastly, where did you purchase that pack? Usually that’s a sign of “bad work” doing. But you can probe your discharge wire with a multimeter and measure the voltage and see if it still gives you the 12s voltage.
Thank you for your answer. The short circuit was fixed, i changed the dc port, and the vesc came with factory error, replaced it too…
Voltage is 43 volts now, but it is on 10%. We mesaured all series, it balanced…
I bought it from china, but not was the cheapest.
My other battery from there works perfect, but it is only 10s2p.
Vesc company recommended me to put fuse to discharge wire, one 120a fuse per vesc (240a total).
Is it possible, the battery construction can’t handle 20-30a and then burned? I think i didn’t drown more than when i tested…
No, It looks as if the burnt was from the nickel. But I do not recommend adding the fuse. If that broke during your ride, let’s just say this would be our final conversation. The battery construction looks iffy, however, if you can charge it and then do a quick test with a different vesc-based esc, you can check whether or not it can do 120A. Although, that only does 90 amps max.
I think a second opinion would be helpful here as well.
Those pieces of nickel may not be enough for the load you’ve got on them there.
What size is it? How much current was going through it?
That battery is built poorly. They only used one thin nickel strip for the series connctions. At 20-30A that tiny strip just can’t handle the current and get’s super hot. That’s probably why it melted the heatshrink.
The best option would be to have a decent battery builder rebuild that pack.
the plan is to take a 25mm nickel strip (largest i have atm) and fold it over the edge of the p group then solder to it.
the other option is to solder first and then weld
edit: also for alcohol is there something else i can use (dont have any atm) maybe acetone or something similar
is it worth putting 21700 rings on the negative side to help protect them where the wrap got ruined slightly? thanks
Is that a hole in the cell? If yes, that’s pretty bad…You’d have to replace that one 
nope
bad picture quality and is just the place where the weld was
i sanded it a little more and its gone so i dont think its a hole
(i checked all of them for holes)
what other things do i need to do before welding?
Solder over the hole and it will seal it
Just make sure you have sanded to make sure solder takes will be fine.
heat + cells = bad
no hole anyways so doesnt matter
I’ve soldered thousands of cells and I’m still alive and cells still working as they should be, think your being a bit patantic. A small bit of heat for a few seconds does nothing.
A hole does matter it will start bubbling as it leaking.
I’ve made batterys from recycled cells With holes and they all start to leak and they loose the capacity of the cell.
Don’t solder on cells.
Do solder cells its perfectly fine.
What do you think welding does? generates heat 
soldering on cells is fine, I’ve never seen a datasheet on a cell that’s says do not solder.
I solder every pack I make then every cell can be used for another day unlike welding, where the cel can be danaged when nickel is ripped off and holes made.
looking better? (did everything that people told me) single piece of 25mm wide 0.2mm nickel folded on the side for soldering to
added extra welds for strength (8 per cell instead of 6)
What the fuck dude?
Soldering cells will degrade their chemistry & stability each and every time.
Here is a graph that shows plenty degradation based on your average usage temp.
Effect of Temperature on the Aging rate of Li Ion Battery Operating above Room Temperature
@Battery_Mooch probably has better sources.
