18650 best soldering technique?

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ajw22

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I've tried several soldering irons andall sorts of soldering techniques. I've developed my own, which I believe is superior to anything I have seen on YouTube. It's certainly not how I learned to solder "properly", but it seems to work best for 18650s. And no, the solder is not "balled" - the contact is solid and cannot be simply scraped off.

See video in link
https://drive.google.com/file/d/1l7_27rwvympgwB3sQa-rqzcsUvJLoX0V/view

Soldering iron: 70W Taiyo ElectricPX-401, set to ~390C,with 5mm diameter"large tip for high thermal-storage", but cut at anangle to allow pointed contact.
image_eadgzi.jpg
image_yjwjkg.jpg
image_fegxgw.jpg

Solder: Standard 60/40 rosin core, 1mm diameter

I think this technique works well, because:
1) The rosin has no time to boil away and gets to work immediately, maximizing its effectiveness
2) While the iron is fairly massive, the actual contact area is small at perhapsjust 3mm diameter, thus heating all the area I need and not more.
3) The molten solder ensures maximum heat transfer to the cell surface in the shortest time, as opposed to pre-heating with a "dry" tip and then applying solder



The negative side is a bit more challenging, because some of the heat gets drawn into the cell. But it's basically the same procedure. Just a little steeper angle to make the contact area smaller, and perhaps 2 seconds of contact. Hopefully ending with something like this:
image_hyfiii.jpg
 
The "best soldering technique" for Li-ion cells is:never solder to cells - it may greatly compromise safety.Instead you should use a spot welder likethe pros do (they're cheap nowadays). Soldering directly to a cell can make them much more dangerousby possibly compromising basic safety mechanisms such as the CID (which uses a penetrationweld), or the separator, etc. Every reputable cell manufacturerwarns pack manufacturers not touse soldering, e.g.see theexcepts below fromdatasheets:

LG
Do not solder on battery directly

Samsung
Don't heat partial area of the battery with heated objects such as soldering iron.
6.1.1 The cell should not be soldered directly with other cells. Namely, the cell should be welded with leads on its terminal and then be soldered with wire or leads to solder.
6.1.2 Otherwise, it may cause damage of component, such as separator and insulator, by heat generation

Sanyo/Panasonic
11) Soldering
Do not directly solder the battery.
The insulator could melt or the gas release vent might get damaged from the heat.
Additionally, the battery may catch fire, smoke, heat generation or explode.

Sony
Do not disassemble, remodel, or solder.
Do not solder lead directly to the battery body.
Do not apply solder directly to cells.
Under no circumstances should wires be soldered to battery terminals to enable use with other equipment
Do not puncture batteries with nails, strike them with hammers, step on them, or apply solder to them
 
The required amount of heat to make the CID fail would be a *lot* for a soldering iron, considering the POS connection end is held up off from the rest of the cell.

If using a high enough massed iron and at least 60W, the time the iron is on the cell is not long enough to melt any of the plastic if the iron doesn't touch the shrink wrap in the first place.

The time that an iron should be allowed to make contact with a cell is NO LONGER than 3 seconds. Even 2 seconds is approaching the limit. This why it is imperative to have an iron with sufficient mass and heating wattage to transfer the required heat to melt the solder to flow. Place the solder wire on the cell, then apply the iron tip. The solder should flow almost immediately. Once it does, pull the iron off.

On the Pos end, you have a little more time, 4 seconds max. On the NEG end, 3 seconds is absolutely max time allowed.

Spot welding can be just as dangerous, if not MORE so, than soldering. A spot welder can burns holes straight through the casing. It is possible to cause holes and not even know it if there is a piece of nickel strip on top. It doesn't take much of a hole for electrolyte to get through.

For beginners, I would recommend soldering first. Then later on graduate to a welder. You can go straight to spot welding if you have plenty of bad/dead cells to test with to get the proper feel for it. And it's not weld 10 cells and you're a pro. More like 100's before you get the proper feel for it.
 
Korishan said:
Spot welding can be just as dangerous, if not MORE so, than soldering. A spot welder can burns holes straight through the casing. It is possible to cause holes and not even know it if there is a piece of nickel strip on top. It doesn't take much of a hole for electrolyte to get through.

For beginners, I would recommend soldering first. Then later on graduate to a welder. You can go straight to spot welding if you have plenty of bad/dead cells to test with to get the proper feel for it. And it's not weld 10 cells and you're a pro. More like 100's before you get the proper feel for it.
I won't disagree ... it took me a bit of effort to learn spot welding. I did indeed practice on throwaway cells, and I started with a value I knew would be too little and slowly worked my way up.

I recently tore apart a pack I made (the first pack I made, actually) and I'm happy to say that the attachments were quite solid without burning through, and the cells have not appeared to suffer any damage (including to capacity).

I use the Malectrics spot welder, driven by a LiPo pack (selected just for that purpose).
 
Korishan said:
[...] For beginners, I would recommend soldering first [...]

That'svery dangerous advice, I strongly encourage anyone who values safety to follow the prior posted warnings of top-tier cellmanufacturers, viz.never solder directly to Li-ion cells.

Korishan said:
The required amount of heat to make the CID fail would be a *lot* for a soldering iron, considering the POS connection end is held up off from the rest of the cell [...]

On the Pos end, you have a little more time, 4 seconds max. On the NEG end, 3 seconds is absolutely max time allowed.

What is the basis for your belief in these claims? Do you seriously think you know better than the scientists and engineers who design and manufacture the cells?
 
Considering that there have been literally 10's of thousands of cells that have been "soldered" on in this forum, and only a handful of cells failed, AND those cells failed because of lazy or improper soldering, then I think the "forum experience" speaks for itself.

As for spot welding, I have seen a LOT of people on this forum that have punctured holes in their good cells even after a few 100 spot welds have been done. So again, I say the forum's experience speaks for itself.

And, considering several members of this forum have done extensive tests of varying degrees as to how much heat, how much solder, how big of an iron, etc, etc, again, the forum speaks for itself.

Many knowledgeable people here, "including" (with actual legal degrees) Electrical Engineers, Space Engineers, Electrical Chemical Engineers, and many other types of very knowledgeable individuals. I don't recall all their names, but you can go through the "Introduce yourself" section to find them.

I know that both of you "khauser" and "gauss163" are new to the forum, not even a month here. Maybe a little bit of history reading would recommended of past experiences.
 
I think all i did was relate my experience. I have not offered much of an opinion on the safety side of this debate because I don't know. I do know heat kills, and I personally am more comfortable spot welding.
I certainly didn't mean to offend you or anyone else.
 
No offense taken.

I agree that heat kills. And so can a spot welder. Not everyone is as experienced with a spot welder as another. That is why I recommend a "newbie" start off with soldering. Or at least test spot welding on lots of bad cells.

In a recent video by Lithium Solar, he shows that one of his cells developed an electrolyte leak. It destroyed 2 of his cells. They were almost brand new cells. He spot welded those cells. It is possible that perhaps he poked a small hole in the cell while spot welding. I don't know. I don't have the cell to inspect it, and I don't know if he has the equipment to inspect it.
However, I am just noting that even an experienced spot welder (he's done 1000's of welds if not 10's of thousands himself) can poke holes in a cell with a spot welder. At least with a cell that has gotten a little hot from soldering will just slowly deteriorate over time and can be replaced w/o damaging other cells. A leaker will damage other cells around it. Something to watch out for
 
Korishan said:
Considering that there have been literally 10's of thousands of cells that have been "soldered" on in this forum, and only a handful of cells failed, AND those cells failed because of lazy or improper soldering, then I think the "forum experience" speaks for itself [...]

How do you know that somehaven't failed? It is quite common thatfolks are too embarrassed to publicly admit theirmistakes.

Unfortunately it is likely the case thatsome soldered powerwalls are ticking bombsand willfail down the road, since the effects of such cell damage may take many cycles to rear its ugly head.

Of course it's a very personal choice just how much risk one is willing to take. But, relativelyspeaking, likelythis is not far fromplaying Russian roulette.

To those who may not know: while it is easy to extinguish small pack fires with water (it's therecommended way), you'll have no hope of doing likewisewith a huge pack like apowerwall (you may haveheard reportsabout Telsa packs reignitingdays and even weeks later in junkyards). Huge pack firesare difficult to control even by professionals - not to mention the extremely toxic fumesfrom Li-ion fires - which can cause serious permanent damage fromeven a single whiff.

I wouldn't let my loved ones anywhere near a soldered powerwall. Far, far too risky.

Korishan said:
In a recent video by Lithium Solar, he shows that one of his cells developed an electrolyte leak. It destroyed 2 of his cells. They were almost brand new cells. He spot welded those cells. It is possible that perhaps he poked a small hole in the cell while spot welding. I don't know [...]

Do you have a link?Such leaks can be caused by many factors, most having nothing to do withspot welding.
 
We highly recommend that no powerwall be put anywhere near a home, vehicles, or where property damage to yourself or others could occur. We always advocate putting the power bank in some sort of external building. This is regardless if using new or used cells.
So yes, we agree to not put any of these near our loved ones.

Even spot welded pack could fail. We also don't know if the failure was due to the welding, the soldering, or the failure of the cell itself for some other reason. So you cannot say with 100% certainty that a soldered cell will fail "because" it was soldered. There is absolutely no way to know for sure.

We also know that using high volumes of water is how to "contain" these fires. There is no way to "put them out" as they provide their own oxygen. Only thing we can hope is to contain the blaze until it becomes cool enough that the chemical reactions cease.
These fire can happen with spot welded packs just as easily as it can happen with soldered packs. Again, we don't know 100% sure if the cell went rogue and short circuited itself, if there was a solder ball under the cap, if there as a spot weld that actually blew a hole in the casing and caused corrosion to the point of self igniting. We just don't know.

As far as videos go, here's Lithium Solar's Pack:
Also, just for added bonus material there is also DIY Tech & Repair's video:


And something to take to note, just because the "casing" got up to 60C does not mean the internal part of the cell reached that temperature. I have not seen a video those shows how much heat goes "into" the cell rather just along the casing.
I reviewed about 10 random cell datasheets to see what their temp ratings were. Every one of them was 60*C. If the "casing" only reaches 60C for a few seconds, that is no where near the "operating" temperature of the internal of the cell. And I would consider operating cell in an environment longer than a few seconds.
 
Korishan said:
[...] These fire can happen with spot welded packs just as easily as it can happen with soldered packs. Again, we don't know 100% sure if the cell went rogue and short circuited itself, if there was a solder ball under the cap, if there as a spot weld that actually blew a hole in the casing and caused corrosion to the point of self igniting. We just don't know [...]

And something to take to note, just because the "casing" got up to 60C does not mean the internal part of the cell reached that temperature.

Yes, of course, fires can happen in any pack for motley reasons, but that implies little about the matter at hand. All reputable manufacturers strongly recommend against soldering (cf. post #3) because it isinherently much more dangerous than spot-weldingdue to the much higher risk of internal damage due to the much greater thermal load while soldering.Understanding precisely whythat is truerequires a fair amount of expertise- so it's better todefer to expert knowledge on such rather than insteadrely on anecdotal evidence(such as "I've done it a lot and nothing bad happened yet").

As for making guesses about the temperatures that cellcomponents may reach during soldering, and what consequences that may have on safety, that is probably difficult evenfor experts. When it comes to matters of safety, it is best not to rely on guesses. Better to be safe than sorry.
 
Manufactures also state that the cell should *never* be used outside of its original design/pack. Which means, "we" are using them against the manufactures recommendations as we are using them in a way that they were not meant to be used for.

And, they probably only state that to cover their own butt. It cuts drastically down on manufacturing accidents. Mass production "obviously" requires spot welding. It would be stupid to do soldering on an industrial scale.

Also, for making guesses that spot welding is the "only" way to go because it "might" cause damage to the cell is just as blind as saying soldering causes damage to the internal structure of the cell. As you yourself noted, "that is probably difficult even for experts". So therefore, your anecdotal dogmatic approach about stating that spot welding is the "only" acceptable method is not solid enough.

Perhaps after doing loads of tests you can come back with the results with videos and graphs and maths to back up your claim.
 
Korishan said:
Manufactures also state that the cell should *never* be used outside of its original design/pack. Which means, "we" are using them against the manufactures recommendations as we are using them in a way that they were not meant to be used for.

And, they probably only state that to cover their own butt. It cuts drastically down on manufacturing accidents. Mass production "obviously" requires spot welding. It would be stupid to do soldering on an industrial scale.

Apples vs. oranges. The "never solder to cells" warning is in datasheets, which are targeted at battery professionals (engineers, pack manufacturers, etc) who are presumed to already have requisite expertise on design and manufacture of battery packs, but who may well lack the lower-level expertise yielding intuition that soldering may internally damage cells, making them less safe. Iirc in the old days there were some incidents due to cell soldering before the dangers became common knowledge among such professionals (long before consumer use of Li-ion cells became common). There would be no reason for such soldering warnings if it were merely inefficient ("stupid on industrial scale"). Rather, the warning exists because soldering to a cell may make it less safe - not only in end use, but also in pack assembly, storage, and transportation.

OTOH, the recent warnings on cell labels are targeted at consumers - spurred primarily by the widespread adoption of cells in vaping. As the many recent vaping accidents show, Li-ion cells generally are unsafe for use by a layperson without any special Li-ion knowledge, since they typically wrongly assume that they are just as safe as other common consumer-level cells.

While it is possible to remedy the latter problem by better educating consumers on Li-ion safety (as someof us attempt to doin various hobby forums),there is no analogous workaround for the soldering problem because the deficiency is an inherent property of current cell design. They simply are not designed to handle the much larger thermal load imposed by soldering. That may be fixable with new designs, but there is little motivation to do so since there is no demand for such by professionals.

Korishan said:
Also, for making guesses that spot welding is the "only" way to go because it "might" cause damage to the cell is just as blind as saying soldering causes damage to the internal structure of the cell. As you yourself noted, "that is probably difficult even for experts". So therefore, your anecdotal dogmatic approach about stating that spot welding is the "only" acceptable method is not solid enough.

My point was simply that what's difficult (but doable) for experts may well be hopelessly impossible for novices. You are questioning advice of experts based on what? Do you have their deep knowledge of battery electrochemistry and cell design and manufacture? If not then why do you think it is wise to ignore such sage advice, esp. when it comes to matters of safety - where wrong guesses could wreak havoc?

It seems you presume that the experts recommendations against soldering are "blind guesses". But that's not typically how we scientists make logical inferences. I don't know offhand if they ever did rigorous studies on such, but if they did they were probably so long ago that they are unlikely to be accessible online now (and probably only available to OEM partners - like much data from manufacturers). If there is interest I could elaborate on possible reasons that may be behind such inferences, but I'd rather not waste my time doing so if it will simply be (wrongly) quickly dismissed as "dogmatic", seemingly without careful consideration.
 
gauss163 said:
OTOH, the recent warnings on cell labels are targeted at consumers - spurred primarily by the widespread adoption of cells in vaping. As the many recent vaping accidents show, Li-ion cells generally are unsafe for use by a layperson without any special Li-ion knowledge, since they typically wrongly assume that they are just as safe as other common consumer-level cells.
Like the warning label on a hairdryer, "Don't operate in the shower"

gauss163 said:
They simply are not designed to handle the much larger thermal load imposed by soldering. That may be fixable with new designs, but there is little motivation to do so since there is no demand for such by professionals.
As in the current technologies, or the ones that were in effect "in the old days"?

gauss163 said:
You are questioning advice of experts based on what?
I'm not questioning "experts". I'm questing what you have proposed as being from experts. The link you posted above it to more of your viewpoint in another forum, not a tech document or datasheet that backs up what you are starting. At this point, what you have said is basically here-say.

gauss163 said:
Do you have their deep knowledge of battery electrochemistry and cell design and manufacture? If not then why do you think it is wise to ignore such sage advice, esp. when it comes to matters of safety - where wrong guesses could wreak havoc?
No I do not have "deep" knowledge of the designs. But what I do know is that there are companies that still solder their cells. I know that there are people who are capable of applying the proper amount of heat to a cell during solder so as to not damage the cell. In several videos there have been thermal recordings of soldering and spot welding. In both instances, the cell never got over 50C. Even the spot welding ones reached close to 45C. Even spot welding incurs heat into the cell. However, spot welding also "can" damage the cells physically in a way that is not noticeable to novice just as soldering can. So for a "novice", both methods can not be compared or one made better than the other. It only takes a pin prick of a hole from spot welding to make the cell super dangerous. At least soldering you know relatively immediately if you got some solder inside the Pos cap. There is no ticking time bomb

gauss163 said:
It seems you presume that the experts recommendations against soldering are "blind guesses". But that's not typically how we scientists make logical inferences. I don't know offhand if they ever did rigorous studies on such, but if they did they were probably so long ago that they are unlikely to be accessible online now (and probably only available to OEM partners - like much data from manufacturers). If there is interest I could elaborate on possible reasons that may be behind such inferences, but I'd rather not waste my time doing so if it will simply be (wrongly) quickly dismissed as "dogmatic", seemingly without careful consideration.

I do not presume it's "blind guesses". Again, I haven't seen any articles pointed out by your previous comments as to your backings. Currently, you have only said what "you think" to be accurate. Please back up your claims with accurate information, not links to other forum posts.
It is only made dogmatic when there is no evidence to the information presented. Please share your information with relevant data referrals (in its own thread though, please).
 
Korishan said:
I'm not questioning "experts". I'm questing what you have proposed as being from experts. The link you posted above it to more of your viewpoint in another forum, not a tech document or datasheet that backs up what you are starting. At this point, what you have said is basically here-say.

But you do appear to be questioning experts, sinceabove I posted in this forum excerpts of datasheets from all top-tier cell manufacturers that explicitly warn not to solder on cells. That's not "here-say" [sic].

Korishan said:
No I do not have "deep" knowledge of the designs. But what I do know is that there are companies that still solder their cells [...]

Please give some evidence supportingthat claim. I don't recall ever seeing such soldering by any reputable company.
 
I have yet to see a post about soldering vs spot welding.
 
I have soldered all my packs with no issues. Over 8,000 cells and counting....

Oldest batteries (3,300 cells) are 2 yrs old with730 charge/discharge cycles with average 40% DOD.

The proofis that there has been
1) no loss of pack ahfrom pre-solder (adding up the ah of individual cells)to post solder (discharge test)
2) no noticeable degradation on the 2 yr old packs
3) no balance required between the 2 yr old (3,000 cells) batteries and the newest battery (~1,400 cells) with 30 cycles.
which indicates a healthy set of packs!

I use/used 100w Weller -https://www.amazon.com/gp/product/B002I7X7ZS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
and(self fluxing)solder -https://www.amazon.com/gp/product/B07KWDYNLV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
which allows for quick soldering.

I do agree that spot-weld can be faster - but you have to get proper spot welder / technique all lined up :)
 
OffGridInTheCity said:
I have soldered all my packs with no issues. Over 8,000 cells and counting....

Oldest batteries (3,300 cells) are 2 yrs old with730 charge/discharge cycles with average 40% DOD.

The proofis that there has been
1) no loss of pack ahfrom pre-solder (adding up the ah of individual cells)to post solder (discharge test)
2) no noticeable degradation on the 2 yr old packs
3) no balance required between the 2 yr old (3,000 cells) batteries and the newest battery (~1,400 cells) with 30 cycles.
which indicates a healthy set of packs! [...]

Such anecdotal observations don't "prove" anything other than you are very lucky that nothing bad has happened yet.

We don't know how much soldering on cells increases the risk of future dangerous events. It may well be hundreds or thousands of times more risky. If you chooseto ignore the manufacturers' warnings and expose yourself to such risks than that's your prerogative. But if you seriously value safety matters then you should heed the warnings of all top-tier manufacturers to neversolder directly to Li-ion cells.

Also worth emphasis: such risks are likely compounded by other highly risky practices, e.g. some hobbyists attempt to use cells that have been severely overdischarged - which is also prohibited by manufacturers (most datasheets warn not to chargecells that are below 1.5 to 2.0V, though iircone goes down to 1.0V). The damages caused by both this and solderinglikelyinteract in ways that may increase the risks even further. Andmany of the cheap BMS used are very low quality and further compound the risks.

As always, it's better to be safe than sorry. But the best I can do is guide you to knowledge that may helpyou to make wise decisions. The rest is in your hands. I sincerely hope that you don't lose them due to unsafe practices.
 
Will respectfully disagree. My results are consistent withmany battery packs/powerwalls built overthe last 4 years as evidenced by many youtubes + the experience shared on this forum. I would not call this history of success'anecdotal'. Here's an interesting youtube investigating solder/heat in practical terms -https://youtu.be/G9WNutq6PV0

Remember that warnings are not the same as actionablefacts in DIY powerwall terms. For example, these Ring batteries have a 'severe warning'

image_luyvrt.jpg

but they absolutely perfect forDIY powerwalls :)
 
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