Spot welding A123 26650 cells

May 2014, I bought 220 pcs of A123 cells straight from the factory for my second e-bike, the price was good, and I had some extra cash.



Later, in 2015, I bought JP welder kit, serial number 2-1. After soldering 2 packs for my first e-bike, I knew there's got to be a better way.

In 2017 I got my electric Ford Focus, and ebike project wasn't on my mind anymore.
Cue in COVID. April 2020, tons of free time, I've decided to finish ebike #2.
Assembled welder kit, but due to barely readable markings on ICs, screwed it up.
Bought new ICs, and a programming kit for it.
Programmed it, soldered again, voila, it works!
Got a used car battery for it, but it barely had the power to weld 0.15 nickel strips together.
Fair enough, went to local Costco, got the most powerful battery they had, 150Ah, 850 CCA at -17C, 1100 CA at room temperature.
Worked like a charm.



Next problem, A123 26650 have AL can, with the negative side being a small piece of nickel, but the positive side is the whole body.
And apparently, you can"t spot weld to the aluminum, you need fancy equipment like an ultrasonic welder, they cost about U$40k. and up.
Even Jakov mentions this:



Bummer. More googling ES.

Eventually, cell_man post from 11 years ago, how A123 cans have a small round piece of nickel laminated to the positive side, and it's possible to solder nickel strips to it.



Hallelujah!
With my powerful battery it works!
Only took me 7 years

Next, I've made a holder for the electrodes, thinking it will improve my welds, but no dice.
Couldn't get proper contact on both electrodes at the same time.



Back to the manual welding.
Works great, thanks a lot Jakov for an awesome product!






Next is finally spot welding the battery for my ebike this weekend.

That is one long journey!
But it appears to be worth the wait.
Keep us informed...

M

What nickel you used for welding?
I tried 0,25mm nickel and could not get it to weld to positive side, even with 250J using K-Weld with my 11,8V ultracaps delivering 1761A within 166ms. It sticks but I can tear it apart easy with hand.

But then I splitted the nickel and voilla, welding two separate nickel strips with 150J and 99ms and 1746A it stick and tearing apart was hard and nickel strips got holes inside after that.
So I have to cut 10mm wide nickel in half and then weld it that way

0.15 nickel strips.

You're welcome, really glad you like it!

150Ah seems a bit to much, but since it didn't blow right away it is probably fine, CCA number seems fine.

nuxland said:

But then I splitted the nickel and voilla, welding two separate nickel strips with 150J and 99ms and 1746A it stick and tearing apart was hard and nickel strips got holes inside after that.
So I have to cut 10mm wide nickel in half and then weld it that way

Click to expand...

I got a similar experience at 1700A it starts to stick better. I use .2mm nickel with a slid. But the weld nudget is still small, it is not about the joules but about the amps. The aluminum under the thin nickel plate on the plus terminal of the cell is conducting the heat away from the weld very fast so you need much power to put in the weld to get sufficiently high temperature. The pulse time is less critical.

nuxland said:

But then I splitted the nickel and voilla, welding two separate nickel strips with 150J and 99ms and 1746A it stick and tearing apart was hard and nickel strips got holes inside after that.
So I have to cut 10mm wide nickel in half and then weld it that way

Click to expand...

I got a similar experience at 1700A it starts to stick better. I use .2mm nickel with a slid. But the weld nudget is still small, it is not about the joules but about the amps. The aluminum under the thin nickel plate on the plus terminal of the cell is conducting the heat away from the weld very fast so you need much power to put in the weld to get sufficiently high temperature. The pulse time is less critical.