The battery builders club

[massy]

Sounds plausible. At this point my engineering brain basically just wants to know what’s going on. I’m 99.9% sure all cables, voltages and batteries are fine as I’ve measured voltages and checked continuity with a multimeter. In addition they act as expected 100% of the time when I do not connect the charger.

So realistically it should be the BMS, charger or the cables in between those that plays tricks on me. It’s at times like this I wish I had an oscilloscope at home.

Leaning a lot towards the charger injecting some kind of interference that the BMS in turn does not have proper protection against. And that the crap fuse holder might be what triggers the charger to get into that faulty state. Actually worked with certifying some products in an EMI lab a few years back and it can cause the weirdest of issues.

I will try and measure more when I’m back home or just apply to be on the next season of unsolved mysteries on Netflix…

[SternWake]

A different 10s charger/power supply could be an easy way to test the hypothesis.

Might also see different results if charger is in CC or CV mode.

[Soflo]

Looking for a roll of fish paper that’s cut to length for 21700 cells.
I usually buy a roll on ebay and cut it myself. After a buddy had some precut, I’d like to locate that

[yoyotinker]

Looking for some feedback on my welds so far - any advice/tips y’all have on these welds so far? Kweld on 0.2 nickel.

Negative tear looks less than optimal, but worried about splatter/punch through that seemed to start at 50J. Should I aim for more power on the negative terminal?

Am not sure who I should tag - are there any weld/battery experts I should specifically seek advice from?

Positive terminal:

Negative terminal:

Positive terminal tear:

Negative terminal tear:

[jack.luis]

They’re a lil hot imo

Try some less energy

[yoyotinker]

I’ll lower the power and see if weld strength remains. Is the visual indication of a nickel tear important? (Not the spot, but rather the flake/fragment)

Is the tear on the far left positive weld ok? That was at 45J.

@yoyotinker

Positive terminal tear:

[Pecos]

Long delivery time but good product:

Fish paper gaskets

It is the thinner type of fish paper which is preference and the adhesive is pretty good

[Pecos]

I think those look good if a little hot. I would turn it down 5% and retest. Also there is a small no no zone on the negative terminal dead center. It is small iirc only 3mm and a dead bullseye so best practice is to spread the negative side weld pattern out a bit so it’s harder to accidentally place a weld there.

[hatman]

The angle of the rods is super important. 45 degree works well I’ve found

[SternWake]

I believe the ideal angle the rods are held, are dependent on the shape, and size of the tips, and the downward pressure applied.

Both are pretty big variables to consider.
Along with how tip shape changes slightly with each weld.

Non kweld users need to factor in the welding battery losing some punch after many welds too.

My consistency goes way down when my weld battery us 11.7v or below, and its 12 awg leads from battery get super hot.

[yoyotinker]

Alrighty- so what do we think about these, compared to the ones I posted earlier?

Positive weld:

Negative weld:

Positive tear:

Negative tear:

[jack.luis]

Better but still a bit hot. I say turn it down a lil more

[yoyotinker]

How do these look compared to the ones above?

[jack.luis]

This is the result ( cell on the left) you’re aiming for, so you’re headed in the right direction

[yoyotinker]

Gotcha.

None of the negative welds have torn out like that - have tried 30J-50J in 2.5J increments.

I believe this is because the negative terminal/casing is made of aluminum. How do you think I should proceed?

[SternWake]

What cells are those? Reclaimed Tesla?

The three lines are from high frequency friction, or laser welding?

Perhaps wider, more blunt tips, and higher joules, is worthy of an experiment.

[yoyotinker]

Yes - ex-Tesla cells.

My kweld tips are quite blunt (as-shipped)

[SternWake]

They do look blunt.

Perhaps try use less pressure on them so they dont sink into the nickel as much, and weld over a wider area?

[yoyotinker]

I tried using less pressure with a slightly higher power, but the nickel ends up splattering. Similar to the 3rd from left weld here, but it was farther apart.

@yoyotinker

Tbh, I’m considering sticking with the newly found lower power setting on the positive side, as shown on the left side here:

@yoyotinker

Then using a similar power setting on the negative side, as shown on the right side here:

@yoyotinker

Failsafe could be to raise weld count to 4x or 5x per side.

[SternWake]

Are the cans nickel plated aluminum, or bare aluminum?

Not sure there us any reason to nickel plate aluminum since the oxide which quickly forms is a protective barrier.

If bare aluminum, I imagine the aluminum oxide surface layer needs to be removed, and then quickly spot welded before it can reform.

Perhaps a red scotch brite pad scour followed with isopropyl alcohol wipe would yield better results.