Spot welding LIPO cell terminals

[pullin-gs]

What is technique for spot-welding large pouch LIPO pack terminals together?
Right now I clamp together cells and have had good results. But if I spot weld, pack would be about 30% narrower.
Back in the day when I did RC, I seem to recall that "+" terminals are made of different materal than "-" terminals.

 

[DogDipstick]

One tab is tinnned copper and one is aluminum. Mechanical connections are just as good. Your connections are 30% of the bulk of the pack? Mine are like an extra 5 %.

You burn the tabs easy. then the cell is toast. Impropper technique, overheating, under fluxing can all add up to this. Then you just have a mess on your hands. Also, repairing a damaged connection is tougher with a soldered pack.

OEM cars use ultrasonic welding to bond. Hobbiest do not have this equipment.

Spot welding copper and other conductive is tough. I am experimenting with LG cells... Tungsten... and one of the most advanced spotwelders one can buy for a DIY. When I hit nickel with my spotter the current is 1750A for 15 ms... I try copper and it goes over 2000A and protects the welder... I am going to use Tungsten for its electrical properties in my next attempts. I have alot of cells to weld in a timely fashion.

I have also heard of layering the spot t be welded with a less cnductive layer ( nickel) to increase the resistane and make the weld without overcurrent or damage.

 

[john61ct]

Anyone tried conductive adhesives with fine-stranded boat cable?

 

[pullin-gs]

Here is a 10S1P cell interconnection....note the extra clearance I need between the banks of cells in order to accomidate heavy clamps I use for "P" connections. This pack is used for an E-Trike.
Another pack I built is a 3S3P pack used for my kayak and also for heavy current loads of my Spot-Welder.


My welder draws 500 amps for 20ms .2mm welds in nickle.
Copper I can not do .2mm, so I suppose I will not be able to spot weld these cell terminals. Soldering has always been out of the question for the reasons you have outlined.
I have never even tried aluminum. I expect that would be messy.

 

[pullin-gs]

Anyone tried conductive adhesives with fine-stranded boat cable?

I thought about using copper-tape on a whim, but my better judgement talked me out of it.
I use the tape with solar cells (the hot-silicon-ribbon cells by Evergreen are a bitch to solder!) with EXCELLENT results.....just slap some tape on back of cell, and solder to tape.

 

[spinningmagnets]

Perhaps if you chamfer the holes on the left-side clamping plate, the head of the bolt would sit lower.

Then, you might use a slightly thicker steel plate on the right, and tap threads into it so you would not need nuts on that end.

Some locktight fluid should be adequate to prevent the bolts from coming loose.

 

[john61ct]

Anyone tried conductive adhesives with fine-stranded boat cable?

I thought about using copper-tape on a whim, but my better judgement talked me out of it.
I use the tape with solar cells (the hot-silicon-ribbon cells by Evergreen are a bitch to solder!) with EXCELLENT results.....just slap some tape on back of cell, and solder to tape.

Was thinking more like the very-conductive epoxies, rather than copper tape, no solder involved

As high-AWG wire as you like for very low resistance, "fan out" the fine stranding so each is directly bonded to the tabs, then after curing clamp the tabs to the insulated spacer blocks, wires securely clamped in between.

 

[john61ct]

What strong non-conductive material comes in threaded rod?