So it begins...... Battery spot welder

[sternwake]

   
   

Two layers of 0.15mm copper, no Nickel sandwich
Using 99% of the welder's power.

A 0.1mm and a 0.15mm stack of copper had wider more even welds, at 85% power.

I find it amusing how many high powered esk8's with 18s6p and 14KW of power have just used 0.2mm pure nickel in the past.  

0.25mm copper is equivalent of 1mm of pure nickel.

Tabless cells have such incredible surge ratings that 0.2mm nickel becomes a hot current  chokepoint.

[sternwake]

I was trying to see if welding  0.2mm copper by itself  without the copper brazing paste was possible.

These  practice weld cells came out of my windows 7  pre 2009 era  3s2p  aftermarket laptop battery. Wintonic 2200 mah, 6.6 amp CDR.

It could still power my laptop for aBout 20 minutes, but I needed test cells, so i opened it up.

The little raised portion on the Anode(-) side of can was indented on two cells by the chinese spot welder sometime in 2017.  Those 2 cells hit 2.8v when the other 4  cells were still ~3.5 when I discharged them with the Jaro fan..

So likely compromised by being dented.  I believe the design also allows the cell can to be thinner and weaker, and I managed to destroy two cells by puncturing them welding.

Good thing I had discharged then to below 0.06v first.

     

Siickly sweet smelling electrolyte shot out, and the electrode went deep enough to puncture the jellyroll, into the cathode/anode plastic separator, and melting it and drawing some out of the cell.

I was able to successfully weld 0.2 copper by itself, no flux, to the cathode, but the  copper is pretty weak and whike the welds stuck, I could peel the  copper away from the welds too easily, and thus in my opinion makes it unsuiitable for high physicaL stress batteries like in Esk8 when welded with no flux, no sandwich.

0.25mm copper felt much more than 20% stronger to me, but I think the nickel plated steel cap on top not only makes welding without flux (copper brazing paste) possible, but makes for a more physically robust weld.

My dad had some 316 stainless steel strip, 0.5mm thick in the garage.

I decided why not.

These welds were about 75% of max power, and its likely 60-65% would have been better.
   

The bond to the cell's anode was ridiculously strong.  I couldn't just pull it off with needle nose plyers, I had to roll it off, using a lot of force, but once it started to movee it got easy.

If copper gets a score of 100 in electrical conductivity, pure nickel scores about a 25.
Steel is about 9 or 10, so nickel plated steel is about 10-12, depending on the steel alloy and thickness of nickel plating.
Stainless is about a 5.

When doing  copper sandwich, the higher the resistance of the top cap material, the hotter it gets and the better the spot weld.

So nickel plated steel works better than pure nickel when sandwich welding  pure  copper.

Stainless steel works better than nickel plated steel.

But 0.5mm is ridiculous, but I bet I could weld 0.1copper, 0.5 stainless with the AwithZ P20b welder using the brazing paste, and maybe  even without it.

The DIY500ampdot com proprietor is a good person  and nerds out on stuff like this too.

He is getting some 0.1mm stainless strip and wants to send me some so i can continue exploring the limits of this machine.

Some fancy tabless cells might be in the box too, enough to perhaps upgrade my 7s1p cordless vaccuum battery.  The thing is only 6 months old but It is obviously losing capacity quickly, and i now have  to use a lower speed than i otherwise would to finish the house.

[rvpopeye]

Free stuff. yup yup. He sounds like a good resource.

[sternwake]

I was wrong about the history and composition of the 0.5mm thick  Stainless steel I  spot welded.

My dad got it in the 70's to hold a Tv antenna mast to the chimney.

It is a 400 series stainless, not sure which.
it is quite magnetic, but not as much as mild steel.

I'd like to pay forward the Purple spot welder.

   

It can weld 0.1mm pure copper with 0.1mm nickel plated steel sandwich, equivalent of 0.4mm pure nickel

it can weld 0.2 pure nickel

One needs 2 12v batteries to power it.  One for the Mosfet driver, and one for the welding current

The Mosfet driver battery need not be special, other than it needs an xt90S connector. The S on this connector means it has a resistor inside of it on the positive side, that engages first when seating the connector.  This slowly fills the capacitors and prevents a massive spark which will likely destroy a diode on the circuit board on the 1 or 2nd, maybe 3rd spark.

The weld battery needs to be a 3S, 5.2 to 10.4 AH Lithium polymer battery, with the sweet spot goldilocks battery somewhere in between.

I have not tried a normal 12v  healthy lead acid battery as the weld battery with this welder, as doing so blew up two other welders in this  price category. 

it might be OK if one starts starts on gear 1 and slowly works their way upwards to ofind what ' gear' is actually capable of welding the material they intend on welding.  It might not. it could shoot a flame from a mosfet the first time. i dont know.

but I know it works with a 3S Zee 5.2AH "80C" Lithium polymer battery which can be found for as low as 36$ last I looked a month or two ago

The weld battery also needs an XT90 connector, but it does not have to be the antispark version, unless it is mistakenly inserted into the connector which powers the circuit board.

The 3S Lipo battery cannot be charged above 12.6v, or bad things will happen.

It needs to be stored at around 11.1-3 volts and pretty much never below 10.8ish, though opinions vary as to exact numbers.

Lipo batteries are the most dangerous lithium chemistry but they have very high power density, and are pretty affordable.

That said. This all in one 'Kerpu' welder is being sold for less than the Zee Lipo and can weld 0.15mm pure nickel, and perhaps 0.1 copper, 0.05 Nickel plated steel.

https://diy500amp.com/products/awithz-cp...attery-kit



The copper 'flux' brazing paste will greatly aid the ability to weld 0.1mm copper.

https://diy500amp.com/products/flux-for-...lding-100g

[rvpopeye]

Tempting , my workbench area is overwhelmed with projects piled high on it's ~2sq ft surface . For every finish there is another one layer down arrrrgh ! Even the floor below it is piled a foot or more deep to add any more right now. I am learning a lot about this thx to your experimental mode ..fortunately that only clutters my head lol.

[sternwake]

Mind blown.
previous assumptions proven extremely wrong

 0.2mm  copper  with 0.5mm sandwich weld with some welder power to spare.

The amount.of force required to remove this sandwich was extreme.
   

[rvpopeye]

Weld done ! That wasn't luck though...all the homework guides you.
New Y.A.R.C. title Weldon the Magnificent .
T.W.O.h.s

[sternwake]

I tried 0.10 under 0.15mm copper under 0.5mm SS.

It welded, but pull off strength was not all that great.

The 0.10 welded to strongly to cell, the 0.15 welded strongly to the SS, but the copper did not weld strongly to the copper.

Also stacking and positioning 3 layers then getting the electrodes placed properly atop was annoyingly difficult..

I'm getting some 0.1mm 304 stainless steel on Monday,

0.5mm stainless is ridiculous. I am amazed it works as well as it does.
The goal will be the thickest copper welded with the least energy.

[sternwake]

Experimentation continues.

Triple pulse and gear 950m of 999
0.20ms preheating
02ms interval between pulses

Triple stack
0.15mm copper
0.15mm copper
0.5mm Stainless Steel

   

It felt like a really solid weld, and the brazing paste flux was sizzling for a second after the 3 pulses.

   

Removing the triplestack took an incredible amount of force.

Using this much power seems ridiculous.
   

There is some 0.1mm 304 stainless in route.

[sternwake]

The 0.1mm stainless steel is a game changer in what one is able to weld.

This is 0.2mm copper under 0.1mm stainless steel, no Flux/ brazing paste.
Gear 550, single pulse, no preheating.

   

Ther eis basically no peeling this off the cell without plyers and a lot of force, rolling it off. Pulling straight up will distort the bottom of the cell can.

I see absolutely no point in Using pure nickel, or Nickel plated steel in a sandwich, or by itself for that matter in any battery builds anymore.

I am pretty sure my cheapo Purple spot welder could have  solidly welded 0.15mm copper under 0.10mm stainless steel, and discounting the ampacity of the Stainless steel, which is very low anyway, 0.15mm Copper is equivalent to 0.6mm nickel, and 0.2mm nickel has been considered more than adequate for most every battery build in the last 10 years.

I have performed a few experiments so far using wide flat copper braid.

Solder itself also has about 1/5 to 1/4 the conductivity of pure copper, So its elimination in the series connections between parallel groups can work to further reduce resistance.  
The reason we spot welld directly to the cells is because soldering introduces way way too much heat into the cell, degrading it significantly.  When soldering to the tabs spot welded to the cells, that heat is also transferred to the cell, and is undesirable, but difficult to avoid. not impossible.

Spot welding copper braid between parallel group connections can eliminate that as well, if I can refine the method and technique.

The braid is used as  series connections in Esk8 it is flat and allows for more room inside a tight enclosure( compared to 10AWG, and traditionally braid is hard to solder, lots of heat for too long and the solder can wick across the area which needs to remain flexible, and then break after repeated flexing

This is 0.15mm copper sandwiched around 1.5mmx15mm wide copper braid, using flux, and half the available power of the welder.

   

I have many more ideas to improve on this to experiment with, and a professional has offered to test the resistance of any samples I send him with professional grade equipment and the skills to use it.

There is also a New Cell in town, well, almost in town, its on the interstate due on Friday.

The Reliance RS50 is a Tabless 500Mah cell and performs better than as the EVE 50PL upto 40 amps, and is not far behind it after 50 amps.

Below 10 amps there are only a few Energy cells which can provide more watt hours down to 2.8v, so this thing can be considered a true hybrid, second best at super high power levels and ~4th best at longer slower discharges in total energy delivered in the 21700 format.

https://diy500amp.com/products/reliance-...erformance

Initial cycle life testing is also proving promising, but not conclusive. Yet.