Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
kWeld - "Next level" DIY battery spot welder
#11
Yeah, I was kind of thinking of the same thing, but in relation to the twin holder. Might even make it so that the electrodes dont make contact until you put sufficient force for the brains to recognize there's contact. So the spring wouldn't make contact with the probe and wire, just the probe and housing. Pressing firmly in would make the electrode make contact with the wire (possibly through another heavy duty spring to make sure stays in contact)

Just a thought. Throwing out ideas of possibilities. It's quite possible all my ideas could be bogus in practical application even though they sound good in theory Smile

I'm still interested in the workings of it. (Though, I'm not going to be using it myself, at least not with the powerwall builds)
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#12
(07-17-2017, 04:06 PM)Korishan Wrote: so that the electrodes dont make contact until you put sufficient force for the brains to recognize there's contact. So the spring wouldn't make contact with the probe and wire, just the probe and housing. Pressing firmly in would make the electrode make contact with the wire (possibly through another heavy duty spring to make sure stays in contact)

Just a thought. Throwing out ideas of possibilities. It's quite possible all my ideas could be bogus in practical application even though they sound good in theory  Smile

I'm still interested in the workings of it. (Though, I'm not going to be using it myself, at least not with the powerwall builds)

Much appreciated!

When thinking in this direction, you have to keep in mind that you are dealing with at least 1000A of current. That really is a lot. Despite me being an experience EE with knowledge in power electronics, my first two attempts directly went up in smoke.

For a spring loaded switch this means: either is has to have very good contact, or none at all. If it is somewhere inbetween, you get a weld at a location where you don't want it. I don't think that a reliable construction can be made. Take for example the cable connections. They need to be crimped to the cable lugs with a tool that delevops several hundres of kilograms of force to obtain a reliable connection. (In fact, this results in a cold weld when done properly.)

Thinking of this, another possibilty comes into my mind: a spring loaded electrode, but with a permanent and flexible power connection. Above a given force a sensing switch is actuated. This way you don't need your foot nor a third hand, and at the same time make sure that the pressure is high enough. Make it better and do this on both electrodes.
Reply
#13
Quote:another possibilty comes into my mind: a spring loaded electrode, but with a permanent and flexible power connection. Above a given force a sensing switch is actuated. This way you don't need your foot nor a third hand, and at the same time make sure that the pressure is high enough

I was thinkin of this too, just didn't know how to word it  Smile  I think this one would probably be the best option above all.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#14
Will it spot weld aluminium to a 18650 battery?
Reply
#15
Aluminum is softer than Nickel, so I dont see why it wouldn't. Just turn down the power rating for it. On thing with aluminum is it oxidizes over time, whereas the Nickel doesn't. But, I suppose you could cover the Aluminum with something to keep it air sealed.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#16
Have you spot welded a fuse wire yet ?
One electrode on the wire and one electrode on the battery.
Reply
#17
(07-21-2017, 10:48 AM)1958 greyhound Wrote: Have you spot welded a fuse wire yet ?
One electrode on the wire and one electrode on the battery.
Two customers of mine are using kWeld for this, and after having lowered the minimum energy setting to 0.1 joules it works very well. There is a picture showing this on the product page: https://www.keenlab.de/index.php/portfolio-item/kweld/

I have also tried to weld rotor windings to commutators of small brushed motors, this also works reasonably, but you have to be careful there not to melt the commutator's connecting tabs as well.

But it works a bit different to your suggestion (you would vaporize the wire that way): one electrode goes to the battery, and the other electrode pushes the wire against the battery. Don't slip ;-)
Reply
#18
1958 greyhound: There has been a lot of experimentation over at the electricbike forum (endless sphere). Aluminum and copper both conduct electricity and heat very well. Because they have very low resistance, they do not get hot when passing a spot-weld current through them, Some resistance is needed to get the metal soft enough to fuse together.

Nickel is conductive enough to be useful as a bus material at lower system currents (5A per cell, etc). DIY powerwalls typically have a lot of room in which to build a system, but electric bikes have the opposite problem. They need high range and high power in a small package, so it can fit on a bicycle frame.

For a DIY powerwall, it makes sense to find lightly used 2200-mAh cells for $1, which is only $0.45 per 1000-mAh, especially when you are using hundreds of them. A popular cell for high performance ebikes is the 30Q cell. A new one is expensive. If you find them for $5, that is $1.66 per 1000-mAh. Ebikers gladly pay that because this cell can output 15A, allowing for high amps in a small package.

However, at the high currents that ebikers want, the nickel bus strips become more of a resistor wire instead of a conductor. At high currents, nickel converts much of the battery watts to heat. Doubling the layers of nickel strip is helpful for performance, but it is more expensive, twice the work to install, and still has inefficient performance.

The conductivity of metals is rated against copper (IACS). Copper is 100/100, aluminum is 61/100, but...nickel is 22/100. The shell of an 18650 cell is nickel-plated steel (although to be fair, the current-path is thin). Brass is much cheaper than nickel, it is much more corrosion resistant than raw copper or aluminum. Its conductivity is 28/100 (6 points / 27% better than nickel), but still has enough resistance to be able to spot weld it.

One downside to brass bus strips is that 0.20mm thick nickel is very stiff, but 0.20mm brass is very flexible. You would need cell-holders and a housing to take the strain off of the bus strips if they are brass.

Don't jump into using brass until the experiments are finished, brass buses may require an energy level where carbon electrodes are needed (Don't know yet, I ordered some 1/4-inch carbon gouging rods from Zoro). Also, if anyone wants to experiment with brass bus strips, make two 3mm wide strips and tape them together side-by-side (imagine a 7mm wide strip with a split all the way down the middle). If you use a solid 7mm wide brass strip, the high conductivity will allow the spot-welding current to pass through just the brass, with hardly any flowing through the cell-tip.

https://www.bluesea.com/resources/108/El..._Materials
http://eddy-current.com/conductivity-of-...sistivity/

Concerning spot-welding of fuse wire, fuse wire has two requirements. It must conduct electricity with low resistance at normal amp levels, but when a surge of amps hit the fuse-wire, it must melt quickly. There is a temptation to use a thin strand of copper wire, which is free from a scrap bin. This works, but...copper has a much higher melt temperature compared to fuse wire (1100C vs 300C)

Typical fuse wire for continuous currents below 15A is similar to tin/lead solder ("large current" systems sometimes use copper strand as the fuse, so the spray volume of melted material would be smaller, due to a thinner diameter fuse-wire being adequate a the rated flow). The tiny glass-bulb fuses that youtube "average joe" uses are dirt cheap, and they are they best option if you want individual cell-fuses.

https://www.youtube.com/watch?v=Mrf9nfBBs18

Here is a useful design of electrode holder if you want to use one hand to hold them. The original design had the two aluminum bars solidly clamped together (with electrical insulation between them), but due to the difficulty in getting the two electrode tips to apply the same amount of pressure every time, the two sides can now flex a little in relation to each other.

https://endless-sphere.com/forums/viewto...0#p1336769
Reply
#19
Ordered, very keen to get my head around using it with fuse wire.

Don’t want to solder as my partner wants to help and our Rugrat will be around as well.
Reply
#20
I believe that fuse-wire can be safely soldered onto the positive electrode quite easily with consistent results (cleaning surfaces, proper flux, pre-tinning the cell and wire, 100W soldering iron, etc), if using the proper tools and techniques. However, the negative electrode is quite sensitive to heat damage.

For the negative end, I personally believe that compression, magnets, or spot-welding are the only acceptable methods.

http://www.electricbike.com/inside-18650-cell/
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)