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18650 best soldering technique part2
#11
(08-13-2020, 01:25 PM)DiggsUt Wrote: [...] I don't see what problems soldering heat is causing? [...]

Excessive heat is known to cause various problems, e.g. it can cause decomposition of the electrolyte, and it can cause changes to the separator, etc. These may eventually lead to dendrites, which can (after many cycles) grow large enough to pierce the separator, causing internal shorts and possible thermal runaway.

Unfortunately there is usually no early warning signs of such damage that is detectable by end users. That may occur only when a dendrite tumor grows large enough to cause a short - which could take days, months, or years.

What's plain as day from the linked study is that soldering transfers much more heat to the cell than does spot welding, hence it increases such risks. That's a primary reason why soldering is never used by (reputable) professional pack builders.
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#12
Everyone agrees that correctly spot welding is preferred for many reasons, but I have yet to see anything quantitative that shows correctly soldering yields reduced performance of the cell. Pictures everywhere that say "See! The end of the cell gets hot during soldering!". Um - ya. That's what soldering does, but how does that soldering quantitatively affect the performance of the cell? I can't find a difference after heavy soldering but I'm a hack. In turn, I can't find anything published that shows a difference.

@add - I build bicycle battery packs and dendrites are more of a concern in powerwalls that have low charge and discharge rates. Cycle packs that have high bursts of discharge tend to burn off any dendrite formations. I'm not sure where I saw this discussed. Can't quite seem to find the reference right now.
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#13
^^^ Yes, I too wish there were some quantitative results to chew on. But it's probably not very likely that we'll ever see them since such studies would be complex and quite expensive. Who would have any motivation to fund them? Not the manufacturers since they never solder and have little motivation to consider doing so. Perhaps there will eventually be some university funded studies as recycling receives greater emphasis in the near future. But I wouldn't hold my breath for that.
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#14
(08-13-2020, 02:54 PM)DiggsUt Wrote: I have yet to see anything quantitative that shows correctly soldering yields reduced performance of the cell. ... how does that soldering quantitatively affect the performance of the cell?

(08-13-2020, 03:48 PM)gauss163 Wrote: I too wish there were some quantitative results to chew on. But it's probably not very likely that we'll ever see them

So at this point, the statement that soldering to lithium ion cells is dangerous and should never be done is basically hearsay and just theory. Until solid evidence proves that soldering to cells destroys them, then it is considered a viable option.

With everything, do it correctly. Use just enough solder to make the connection, and just enough heat for just long enough to flow and bond.
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#15
Was doing some research and came across this site: https://www.samsungsdi.com/lithium-ion-b...ation.html

In there it is stated:
Quote:DO NOT charge individual, cylindrical Lithium-Ion Batteries if you are a consumer or end-user.

DO NOT place charger and Lithium-Ion Batteries or Battery Packs under your pillow, on your bed, or on your couch.

This is an example of why we can't "always" trust what their "safety" guidelines are. So, according to Samsung, none of us should be charging Li-Ion cells. We are all consumer/end-users.

And I suppose we are allowed to charge them in other locations, and it's ok. So, looks like you can charge them in garage, on the loveseat, on the table, on the counter, on the carpet, in the clothes hamper, in the dryer, etc.

This falls back on a statement I made earlier. A hair dryer warning label states: DO NOT USE WHILE IN SHOWER.
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#16
^^ Those poor analogies were already debunked i in the prior thread so I see no need to repeat such here.

(08-13-2020, 06:57 PM)Korishan Wrote: So at this point, the statement that soldering to lithium ion cells is dangerous and should never be done is basically hearsay and just theory. Until solid evidence proves that soldering to cells destroys them, then it is considered a viable option.

Qualitative scientific knowledge is not "hearsay".  Since you seem to love analogies, let's apply your "logic" in another subject domain

K-logic Wrote:So at this point, the statement that injecting Lysol to cure covid is dangerous and should never be done is basically hearsay and just theory. Until solid evidence proves that injecting Lysol harms humans, then it is considered a viable option.
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#17
(08-13-2020, 07:28 PM)gauss163 Wrote: ^^ Those poor analogies were already debunked in the prior thread so I see no need to repeat such here.

(08-13-2020, 06:57 PM)Korishan Wrote: So at this point, the statement that soldering to lithium ion cells is dangerous and should never be done is basically hearsay and just theory. Until solid evidence proves that soldering to cells destroys them, then it is considered a viable option.

Qualitative scientific knowledge is not "hearsay".  Since you seem to love analogies, let's apply your "logic" in another subject domain

K-logic Wrote:So at this point, the statement that injecting Lysol to cure covid is dangerous and should never be done is basically hearsay and just theory. Until solid evidence proves that injecting Lysol harms humans, then it is considered a viable option.

You apparently are misreading my comment, either mistakenly or on purpose.

I was "agreeing" with needing qualitative results. Because it appears that there currently is none. Perhaps you should fully understand the comment for what it is before jumping to conclusions and to your limited narrow view of the world. Not everyone is always trying to counter your arguments. If you re-read my comment on results, I quoted you as stating that you hadn't seen any and I was agree we need it.
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#18
I soldered 80 cells to a skateboard pack, took at most 3 seconds per cell on + side and probably little more on bottom side.
heat doesn't last long enough to do any damage.

3 years later, board is still rocking hard with no cell damage. get over it.
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#19
@Korishan I see nothing I misread. Rather, my disagreement regards the (unfounded) method of inference you employed above to attempt to deduce that soldering is a "viable option". As you can see from the analogy, that's not a wise way to make deductions.
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#20
My analogy was not about safety of using lithium cells and soldering. It was in reference to that manufacturers will put warning labels about anything, even if it seems "stupid" to everyone because they are covering their own butts.

Again, you misread what I was stated and inferred my statement was in reference to your comments and safety. Which they were not.
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