Battery Spacers for flat top to button top 18650 are they safe ?

Wurkkos

Gauss163

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Everyone using 18650's should know they're using them outside of what the manufacturer makes them for. Anything we do with them, even just charge them up, is not "officially" recommended. But we all do it. We're taking a risk. Putting a solder blob on them is another risk. Like I already said, keep a bucket of water nearby in case you screw up, and test the cells afterwards to make sure they're performing the same as before.

But this is different. They don't even think that soldering can be done safely by professionals. And the risk is not only when you're soldering. It could cause damage that could rear its ugly head at some future date. As the excerpts from the datasheet warn, it could damage the separator or venting mechanisms. The former could eventually lead to a dangerous internal short, and the latter could cause it to explode like a pipe bomb rather than safely vent as designed. You can't possibly know if such internal damage occurred because there is no easy way to detect it without very expensive equipment, e.g. X-ray / SEM (scanning electron microscope) imaging.
 
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RetroTechie

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Tiny magnets work fine. As you're already doing, just make sure they don't slide around and potentially cause a short.
This (especially that last part). Also:

Afaik flat tops are meant to make it impossible to put unprotected cells in series, because + of one doesn't touch - of a cell placed on top. Hence most unprotected cells are flat-top, and most button-top are protected cells.

As you should know, using unprotected cells in series comes with some big safety issues. Flat tops are a safety feature to prevent fools from heaving those issues. The magnet-on-top method defeats this safety feature. And in general, DEFEATING SAFETY FEATURES IS DUMB.

So don't use this method to put unprotected cells in series configuration! You (or a loved one) could get hurt as a result. Seriously hurt... For single-cell / parallel configuration, no such issues so go ahead & stick a magnet. :)
 

HKJ

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Afaik flat tops are meant to make it impossible to put unprotected cells in series, because + of one doesn't touch - of a cell placed on top. Hence most unprotected cells are flat-top, and most button-top are protected cells.

The battery top and bottoms are made to make welding easy, not to prevent unauthorized usage.
 

Gauss163

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Afaik flat tops are meant to make it impossible to put unprotected cells in series, because + of one doesn't touch - of a cell placed on top [...]

No major Li-ion cylindrical cell manufacturer offers button tops because individual cells are not designed to be assembled into devices by end users. Rather they are designed to be deployed by professional pack assemblers - who typically spot-weld them into battery packs that are professionally constructed and designed to meet international safety standards (e.g. a laptop or power tool battery pack).
 

bigburly912

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I guess I definitely shouldn’t tell you that I spot welded my own 2x18650 pack then. It’s been problem free for 4 years
 

Gauss163

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^^^ I don't see any problem with spot-welding, assuming one has proper equipment, skills, and knowledge.
 
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Bullzeyebill

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I think it has been said that small, rare earth magnets can be used as spacers.
This will keep them from moving.00
Dalton

Good to apply a dab of super glue to edges of magnets, not the bottom. This will keep them from moving.

Bill
 
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