You're free to overheat your batteries, Enderman. The fact that, until now, you've apparently had no issues makes it neither wise nor safe. Sure, you can also grab a powerful bike and run it at 150+MPH on whatever road you may have the guts to too. All these kind of things seem fine until they blow up on your face, sir.
Oh! As I said before, if the solder melts at 94-98°C it actually is a pretty neat safety feature. 
Cheers ^:)
I was recently restoring my niece's laptop battery pack and…
No more shoddy work assembling battery packs with magnets, hot glue and SHARP copper sheets. Soo tight inside the case, a cell wrap got punctured and a pair got shorted :facepalm: . I have a spare couple, but the harm is done :| . By the way, seems a lot of heat actually comes out from the cells' anode, the hot glue keeping the magnet/copper sheet in place melted. Shorted cells heading for the recycling point, @#$%. 
Well, I've ended up ordering a bag of Rose's metal. We'll see how nice is to solder cells with it.
Stay tuned.
Cheers ^:)
They don’t overheat if you know how to solder properly. A couple seconds of contact with a soldering iron will not heat up the batteries more than a few degrees.
Maybe you should check out RC battery packs which have all the cells soldered together:
Soldering batteries is perfectly normal, just because you might not be experienced enough to do it without damaging batteries does not mean that other people shouldn’t do it 
It is safe if you know how to do it, just like everything else in life.
Soldering a battery can be safe and easy
with a really good iron that combines:
- a fast regulation with a good thermal path between tip and heat element,
- enough heat power(80-150W)
Surface preparation:
- cleaning surface with alcohol or very fine sanding
Adding the solder blob to the cell should take only 3-5 seconds at most
The temperature of the iron should be 350dC at most for lead solder, 400 for lead free
Let the cell cool and solder blob the next
Tin the copper sheet or wire
May add some flux to the copper sheet
Heat up the copper sheet or wire
Now stick the copper sheet with iron to the solder blob,
This should take only 2-3 seconds to melt the solder blob
Exactly this +1
2-3 seconds is enough.
Also, a 60W iron is enough, as long as it’s a good quality one and not some overrated chinese potato 
I did a video, the 9 minute long was filmed, but
sadly filmed in 16:9 while my setup was 5:4 damn
here the short one, with a torture test of the solder connection
you can see how short I need to put my tip on the back of the battery
and finally pic after the torture test
the wire broke but solder joint is solid
0K, wasn't all that you said addressed before? Nice pack pics.
We all know how to do @#$% with the right equipment. My latest solders have been done with a 60 chinese watts potato, whose tip was ruined so I ended up rolling copper sheet around it in order to avoid having to sand it down each “couple of joints” or so. Didn't lasted long, though.
Now, go win the Indy 500, Nürburgring, Monaco GP, etc. driving this and you'll be my hero:
Cheers ^:)
did you see how long it took to heat up the 1.65g heavy tip with 80W regulated element when I put it on my handle?
10 seconds
soldering the blob on the bottom of the cell took 5 seconds
the heat reading did drop by 3°C shortly when the regulation kicked in
without regulation the temperature would fall by another 15°C and the connection is done
soldering the wire to blob took 3 seconds
I could have switch off the station during that time still ending up with a perfect solder connection
having the right temperature on the tip not burning the tin
having enough flux
having a clean short fat tip
and you can do this with a cheap 40$ station
a 20$ fixed temperature iron
it just needs enough mass and quality tip to keep the temperature up
thats why many say buy a hakko clone but the original tips
a 200W soldering gun is the worst thing you can try this even if it has enough power the tip has almost no mass
Hello! 
Major update. Received my Rose's Metal from Zhuykoff, and made a little test:
Pools fast and easy over a clean surface, of course. Used Goot Super Soldering Flux.
Über-pleased in amazingness! 
Cheers ^:)
Interesting. Have you done any strength testing yet? I have to say, it’s not pretty though 
Please note that the wire/sheet joints were already done with standard Sn63Pb37. The thing is just a powerbank circuit board testing assembly, on which I previosly was using neodymium magnets and hot glue to connect the cells.
The Bi50Sn18Pb32 joints are quite strong, no measurements done but suffice to say I could tear the copper sheet trying to rip it from the cells with “ease”.
The great news is the cells barely heat up (if barely at all) when soldered with this stuff. 
Cheers ^:)
well, with ANYTHING, and thats any device… most people “concentrate” on what somethng doesnt have, what it doesnt do, what isnt good about it
when i remember to, i try to concentrate on what it has, what it will do, what is (might) be good about it.
i have previously put off soldering onto batteries, simply because i have a chinese french fry, not even a chinese potato, lol… and on top of that i admit to not being a great soldering guy, there i said it.
my combination of having almost the worst tool at hand, combined witha lack of experience to even try to work-around it? makes me pass…
…now, seeing his quick success with rose metal? makes me want to try it… makes me wonder if i could solder a emitter to a thick copper DTP with regular method, then maybe use THIS stuff to solder the pill to the copper board…
i mean, for SOME people, with some tools, and their level or lack of experience? this has possibilities.
===
on a “red-yellow-green” system of ratings? I give this… yellowgreen, or, greenyellow, cant decide at first blush until i try it. Just doesnt look like a “red light”.
my ALTERNATIVE is to buy a better soldering station, and then gain the experience i need, to do somethng i rarely do and would like to dabble with…
sedstar, I presume you'd like to be successful in soldering MCPCBs to copper/brass pills. Having seen how fast a rolled-up (around an old iron's tip) copper sheet turns into a hard to wet black mess of oxidized metal, I bet oxidation may be problematic when heating a chunk of copper/brass over a pan.
So yes, this may be a solution. If you believe its fusion temp is a tad low for your purposes, it can be easily raised by mixing it with pure tin and/or standard cheap lead-free solder (Sn99.3Cu0.7). I say this because, according to the Solder article on the Wikipedia, Sn48Bi32Pb20 fuses between 140 and 160°C, an alloy with a nearly equivalent amount of bismuth and lead vs the Rose metal alloy I bought (Bi50Pb32Sn18).
Cheers ^:)
You should try this out, it's soo amazingly easy!
Cheers fellows
Hey Robinjack, I think it would be a good article if you JUST GET LOST
Hello Barkuti,
I am just beyond newbie level, and I started to slowly gather required materials for LED reflowing (not planning to make solder joints on batteries in the near future).
I looked into some LED datasheets, and I have seen, that e.g. Cree recommends to use only lead free soldering paste to make the reflow.
I ended up buying this Sn42Bi58 alloy:
https://www.aliexpress.com/item/high-quality-100g-Sn42Bi58-SD-528T-low-temperature-SMT-LED-lead-free-SMT-solder-paste-Melting/32824147086.html
My plans including reflow for Convoy L6 lights with selected (better CRI) XHP70 emitters, and for various other lights with 3.5×3.5mm format emitters (XP-L, Nichia 219B/C).
In the recent months, I have read here many cases about someone killed/crippled XHP70 emitters with too much heat and/or steep temperature deltas during reflow (especially the newer XHP70.2), so I assume, it is clearly safer to use Sn42Bi58 instead of Sn63Pb37, because of the 40+ °C lower melting point.
Should I be concerned about this, or it is just a minor factor, and the fact, that presumably the LED manufacturers only recommend lead free solder paste for most of their LEDs means, that it is strongly recommended to use them?
I just ordered some Rose’s metal from here, in the US:
http://www.ebay.com/itm/282261610946
I’m building a pack of 24 Shockli 5500mAh 26650s for an electric bike project. Soldering with typical lead/tin solder can probably be done without significant harm to the cell, but this seems like a better solution. While soldering with standard solder the active material close to the negative end of the cell probably gets close to 200C, and I would imagine this does do some damage locally.
I've never used Sn42Bi58 adam7027, should work nicely but this is just I guess. I'd personally use Sn63Pb37 reflowing over electric induction stove, which I can more or less easily monitor with an IR thermometer to keep it hovering slightly over 200ºC.
To solder with Rose's Metal over steel I use an aggressive liquid flux with helps a lot (Goot's Super Soldering Flux), EasyB.
Cheers ^:)
Based on the material composition it seems to have much worse heat conductivity as well as electrical conductivity.
200C won’t damage a battery if the terminal only gets like that for a few seconds.
There are solders that melt at about 150C too, which are meant to conduct heat and electricity properly.
How much worse is and how does it impact overall performance in our parameters of interest?
”Much worse” is a relative term. A thermal paste is also “much worse” than soldering, but its usage is way more pragmatic for lots of applications.
With an aggressive flux and Rose's Metal it is super-easy to solder copper sheet tabs or wires to cells with massive contact surfaces over their steel (a much worse electrical and heat conductor, by the way) terminals. I am pretty sure this method beats industry standard nickel tab spot welding practices in electrical and thermal properties by a lot. The key here is to determine how vibration resistant is this stuff, so a quick down to earth advice for those after this in mobile applications is to improve solder contact gripping with a file, for example, and avoid blindly relying in the solder contacts as structural support.
To finish off, Rose's Metal and close alloy variants (like my Bi50Sn18Pb32) are relatively affordable if you know where to get them, of course. I bought 75g for $10 (and got an :-) 85g bag, thanks zhuykoff).
Cheers :-D
Cheers ^:)