Anybody knows what this is?

[Salar]

Hi

I made this batteri and after a week, these spots came on. I dont know what is, can somebody tell me what it is?

 

[Comrade]

I dont know what is, can somebody tell me what it is?

It could only be one thing. Electrolyte.

 

[skeetab5780]

I dont know what is, can somebody tell me what it is?

It could only be one thing. Electrolyte.

on the negative side of the cell?

I am certainly no expert but it looks burnt from too much amperage draw, which worries me because I just built a 20s4p 21700 Samsung 40t pack and I doubled up the .15 nickel strip because I had a feeling this could happen

 

[Comrade]

on the negative side of the cell?

As opposed to the positive side? Of course the welds on the negative side are much more likely to pierce the shell.

but it looks burnt from too much amperage draw

That's not what overheating looks like. The discoloration is not where it would happen either. Current doesn't flow like that.

 

[docw009]

Electrolyte has a sweet smell. How do I know? I also punched a hole welding the negative end of a cell, Probe slipped off the nickel, contacted the casing, the power was too high, and kapow, a hole appeared. Killed the cell. Had to bin it safely.

THere are some dark spots on some of the positive terminals. Perhaps the OP only means the discoloration on the negative ends.

 

[amberwolf]

If you can remove the covering tape you will be able to see it more clearly, and if there is a smell, you can detect it more clearly as well.

If it was from overheating, the discoloration would likely be gradual, most intense at the highest resistance point, fading away from that point. This discoloration is that of a liquid with surface tension that has spread out.

Since it is coming from under the strips, it's likely to be electrolyte leaking out of the cell via a hole burned thru the casing by a weld.

If the cells were recycled from something else and one of your welds happened to be on the same spot as a previous weld, it might make puncturing the cell easier. (or if the old welds were ground off, then the entire area is thinner than normal and easier to puncture).

 

[skeetab5780]

So does that mean this was cause by using too much current while spot welding? It does seem like the two spot welding electrodes are too close together on this weld

I have only been using the Kweld for a little over a year so I am still learning about this stuff as I go

 

[Diggs]

I would say it is leaking. I posted a pic below of an old pack that is leaking badly. As well as the clear(ish) electrolyte you can see the same dark brown appearing in multiple places.

 

[skeetab5780]

In that picture it looks like solder flux for the majority of it to me, Not even sure why there is solder on every cell when it was a spot welded pack?

 

[v85]

I`m completely new to this (learning new things), but there is rule to not spot welding on center of the cell (negative end weak spot). That`s the reason nickel strips with line holes. Spot weld abuse with high current, then vibration when riding, also heat when discharge will cause trouble (cell puncture?)

Here photo of structure 18650 cell: https://endless-sphere.com/forums/viewtopic.php?f=14&t=88110&start=50#p1315644