Not sure if Im just hallucinating but

…I recall reading something about if a cell has been soldered(none-spotwelded) once, its not a good idea to spotweld it(even if solder somewhat removed)?

Reason why I wonder this, Sitting on a soldered battery pack - but Im in the thoughts of dissassemble the pack to redo the structure of how its put - for more space.

Anyway somewhere back in my head I recall reading something about that you should never spotweld a aldready soldered cell? Just a really dim memory.

Because what my inital thought was, disassemble the cells and try and clean of the solder and perhaps spotweld it instead.

Anyone sitting on alot of knowledge about this?

Much appriciated -Pontus

mainly a question of heat destroying a cell. How much is too much?

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The left over solder will explode when you Spot weld it. And to remove it properly you will bring a lot of heat into the cell.

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Yeah that makes sense. Mainly curious on to what made the spotweld procedure so dangerous if there was solder and that explains it. thanks !

Not if you use a resistance soldering iron. They cost a fortune and unless you plan on making a lot of battery packs, it’s not worth it. But it’s really the best way to make battery packs.

I just nabbed one of these guys:

Resistance soldering seem pretty damn interesting. From what I understood you can contain the heat alot better so it doesnt spread as much?

Exactly. You spend a fraction of the time on a joint, meaning less thermal damage to the cell than tradition soldering (should be basically none).

You can use copper strips also, which provide less resistance, and can do higher amps. With these new 30T cells and resistance soldering, I think we have the next big thing in electric skateboard battery technology :slight_smile:


Doesn’t really make much difference. You still bring heat to the point where it should be soldered. Only makes a difference for a large area where you have to move around with the soldering iron.

The new 30T cells are outperformed by 2 x 18650 cells. Have less capacity when it comes to volume. And you just simply need a good connection which can be done by quick soldering or spot welding. So i don’t see how this should be the next big thing because by capacity, volume and weight it is worse than what we have already and good connections are already here.

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Good connections with what? Zinc plates? Copper plates are far superior to zinc plates…

Go read endless sphere and look at what the bike guys are doing. Soldering without a resistance soldering iron will result in thermal damage to the cell, no if ands or buts about it.

The 30T cells are 70mm long instead of 65mm, and capacity is not insane. But it’s about the continuous discharge. I’d love to see how you ride in a group ride, cause I knows it’s not like me. 18650s sag too much in smaller configs. The 30T cells will not sag the same. Really, that is the biggest problem facing 18650 battery packs. It doesn’t solve the weak regen break issue that 18650s have also.

Of course 2x 18650 outperforms this one 21700 cell. But the point is to do the same configs as an 18650, you really don’t need that much more space. a 12s3p 21700 (max 120a, 9 ah) + bms would take less space than a 12s4p 18650 (max 80a, 10-12 ah). a 12s4p 18650 pack is hard to fit on a board with a bms and 4 vescs, but the 12s3p 21700 pack with bms and quad vesc, will fit nicely.

You might be fine with 18650’s, but I’m looking at next level performance, not just a toy to ride around on.

If you wana see my race with Moja from enertion, it’s on here if you haven’t seen it. I’m not looking to build a honda, or toyota (no offense to those brands), I want to build a a porsche. It’s the difference between an economical board for the masses vs a high performance sports board for the few who can tame the beast.

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A quote from mooch about the Samsung 30T 21700 cell:

Bottom Line: This is a 21700 cell (21mm diameter x 70mm length) that is an incredible performer, running over 20% longer at 30A continuous than the Sanyo NCR20700A thanks to its incredibly low internal resistance of 10-12mOhms. This low internal resistance reduces voltage sag, letting the 30T run for longer before the voltage drops too far.

We’re going to keep that resistance low by using good copper with a resistance soldered joint.