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Cell Level Fusing w/ 24AWG TCW
#11
(08-12-2020, 06:58 PM)OffGridInTheCity Wrote: FYI - @HBPowerwall just did a fantastic youtube on spot-welding 32AWG fuse wire - https://youtu.be/THVMnyE4yAw    He shows great detail using K-Weld.
Thanks, great video. It seems to me that spot welding TCW thinner than 24 AWG has extremely variable results when welding directly onto cell terminals. The 28AWG proved to be ineffective as well... This nickel strip method looks promising.
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#12
You might look at getting the battery packs into an air tight enclosure to reduce corrosion issues?

Wondering if anyone has thought of (or tried) doing eg 30AWG wire soldered to an eyelet, eyelet then spot welded to cell?
Eg these: https://www.jaycar.com.au/solder-lugs-pk-50/p/HP1350

Agree it's be extra work but....?
Running off solar, DIY & electronics fan :-)
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#13
(08-12-2020, 10:04 PM)OffGridHawaii Wrote:
(08-12-2020, 06:58 PM)OffGridInTheCity Wrote: FYI - @HBPowerwall just did a fantastic youtube on spot-welding 32AWG fuse wire - https://youtu.be/THVMnyE4yAw    He shows great detail using K-Weld.
Thanks, great video. It seems to me that spot welding TCW thinner than 24 AWG has extremely variable results when welding directly onto cell terminals. The 28AWG proved to be ineffective as well... This nickel strip method looks promising.

Just fyi I use 30 and 32awg TCW with a Sunko 790 with zero issues. I've probably done this for over 1500 cells. Once you find the right setting and tip then it's good. The tip that comes in my probe looks like a 10ga wire. I noticed the ones on hbpowerwall is a fat hunk of copper with a very round radius.
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#14
One of the problems with TCW for cell fusing seems to be it conducts too well?
Ie the resistance is so low it doesn't start to heat early enough.
The nickel strip system mentioned seems better because the material is steel/nickel plating so it heats more readily.
Proper fuse wire usually isn't made of tinned copper wire right?
https://en.wikipedia.org/wiki/Fuse_(electrical)
Running off solar, DIY & electronics fan :-)
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#15
It's been a few months since I did this, but I too was initially getting the sparks like you mentioned. There's two things you can try and let me know if they work, as they did for me: 1) be very careful to make sure that your electrode tip is only touching the wire, and absolutely not touching the top of the cell (with 30 ga. wire, it can be hard to tell, but you get a knack for feeling it); and 2) try separating the electrode tips as far as possible on the cell, with one tip on the wire, and one tip directly on the cell. I use the Malectrics spot welder, and I ended up getting good strong welds at the minimum setting (1 ms), I don't know what the equivalent on the kWeld is.
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
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