Spot welding Tesla cells

[msebold]

Hi. Looking for some input from someone who has built a battery pack from Tesla cells, connecting them in parallel clusters via spot welding. The positive terminal of the Tesla cell looks kind of like a small triangle with the tips cut off. (See attached jpg.) I'm concerned it might be a bit of a challenge keeping the welding tips precisely on the positive terminal during a weld. The terminal is small, distinctively shaped, and will be hidden by welding tape. Any advice or tricks anyone has found?

Thanks in advance.

 

[randyc1]

I have spot welded these cells , do yours have the small ring Isolators on the Pos terminal ?

 

[msebold]

I have spot welded these cells , do yours have the small ring Isolators on the Pos terminal ?

They do not, but I was planning on purchasing and using ring-shaped insulation tabs just to be safe.

So, did your spot welding go okay? Did you experience any problems?

 

[Overclocker]

if that a raised dimple? of so then you need to grind it flat with a little stone on a dremel, else the nickel won't sit flat and you won't get good welds

 

[redilast]

I've built a pack using the NCR18650BE cells which are similar to the Tesla cells. Same top. It is more difficult to weld than the tops on a almost any other cell. I used individual hand held weld pens and I can generally feel if I'm about to weld on a hard surface so I don't miss. Out of several hundred welds on the last BE pack I made I only had one small partial blow-through in a tab.

But I agree if you are using used cells you'll want to grind off the small left over weld with a dremel tool or similar will work well.

 

[999zip999]

What welder do you have ?

 

[msebold]

if that a raised dimple? of so then you need to grind it flat with a little stone on a dremel, else the nickel won't sit flat and you won't get good welds

No. There are no raised dimples. The positive terminals are flat, not raised. Thx.

 

[msebold]

I've built a pack using the NCR18650BE cells which are similar to the Tesla cells. Same top. It is more difficult to weld than the tops on a almost any other cell. I used individual hand held weld pens and I can generally feel if I'm about to weld on a hard surface so I don't miss. Out of several hundred welds on the last BE pack I made I only had one small partial blow-through in a tab.

But I agree if you are using used cells you'll want to grind off the small left over weld with a dremel tool or similar will work well.

Wow. Until I ran my finger over the positive terminals I didn't even notice that each cell has a tiny little left-over weld dimple. I'll use my dremel to polish these down. Thanks for the tip.

Also, my welder has a hand-held welding pen, which I suspected I would have to use. I'll go slow on each weld, pressing down gently to make sure I'm firmly touching the positive terminal. Good advice. Thx.

 

[okashira]

The dimple is aluminum left over from the bond wire.
I leave it on. It actually helps you find the center of the cell when spot welding. You press with the welder tips and can feel the dimple. Use enough pressure and the welds will be fine. Dual pulse welder helps to seat the nickel before the weld. (like JP spot welder)

If you must remove it, a knife will pop it off flush.

 

[msebold]

The dimple is aluminum left over from the bond wire. I leave it on....

Thanks for the info!

 

[redilast]

The dimple is aluminum left over from the bond wire. I leave it on....

Thanks for the info!

If you do leave it on, just be careful to position your welding probes so one of them is not on top of the aluminum or you may get tab blow through.

 

[Hwy89]

Just completed two 6p 12s packs with Tesla cells from Okashra. I polished the old welds off and spot welded with my JP welder. No problem keeping the welds on center, you just have to be carefull. What I did notice is that the nickel strip needs to be cut either long enough to lay across the top of insulation on the rim or short so that it doesn't extend past the raised triangle. In between lengths seemed to easily slide under the insulating washer. No sparks but something to watch out for.
Love the new light weight packs. My wife especially appreciates that she can now lift her bike when she needs to. These new packs are replacing 16p 12s laptop cell models that have given us great service for four years.

 

[okashira]

Just completed two 6p 12s packs with Tesla cells from Okashra. I polished the old welds off and spot welded with my JP welder. No problem keeping the welds on center, you just have to be carefull. What I did notice is that the nickel strip needs to be cut either long enough to lay across the top of insulation on the rim or short so that it doesn't extend past the raised triangle. In between lengths seemed to easily slide under the insulating washer. No sparks but something to watch out for.
Love the new light weight packs. My wife especially appreciates that she can now lift her bike when she needs to. These new packs are replacing 16p 12s laptop cell models that have given us great service for four years.

Yes this is good advice.. make sure the nickel strip is long enough to extend past the positive terminal well onto the heat shrink and the washer. True for all 18650's. This way the corner of the nickel won't be at risk of piercing the washer/heatshrink.

 

[999zip999]

Okashira do you add a gasket on the pos end? I do see there is one.

 

[eric1565]

Yes, he does add a washer ontop.