Seems not many of you paid attention to this. I've renamed the thread (supressed “batteries” after “Soldering”) because, well, Sn42Bi58 can make pill soldering a much easier task. Don't you think?
Reflow leds with it for a “free” overheat protection. LoL!
Soldering pill with a gas burner it doesnt make much difference heating to 100 or 200 dC,
Just apply solder paste or some pieces of solder wire on the pill and put the star on top
Its not much different from teflowing LEDs on an aluminium plate you heat up with a gas burner
They are, in fact, the most safe. At 98°, all the solder turns liquid, the battery contacts fall, and you have an open circuit: emergency battery shutdown.
Not true, a flashlight has a temperature gradient starting at the heat source: the led. The solder closest to the led will go first, so the solder under the led liquifies first, no problem because the led is clamped in most of the time, next in line are the ledwires: the led+ pops loose from the ledboard, where will it go? ai, it touches the pill: direct battery short!
Ripe for exposure to intended consequences. If you want to design in a fuse best not to place it where fuse failure creates yet another short(led+ wire, B+ spring).
I was reading about solder alloys a while back and remember reading that alloys containing bismuth have lower melting temperatures but are also brittle. Not a good choice for applications where impact resistance is desired.
From what I have gathered over time (solder types have been discussed before on BLF), our common 63/37 Pb/Sn alloy is a pretty good compromise: convenient melting temperature, tough enough for most joints, cheap, flows and adheres well, better than average heat conductance.
Well, maybe I should have made a more thorough explanation.
It came to my mind Rose's Metal makes an excellent solder alloy for cell interconnection in battery packs. No need for spot welder, and doable with an ordinary soldering iron plus copper sheet/wires. Just heavily wet the copper in the alloy, preheat the “tab” from above and (without removing the iron) place it over the battery terminal until the alloy pools. Less than a couple of seconds.
As I said before, if the pack is correctly assembled and orientated, it would also serve as overheat protection.
This is for general usage. Irrelevant for most flashlights, except maybe for the ones with integrated charging circuitry.
Please note that, with regards to battery pack assembly, this opens the door to new possibilities as there's no need for tabbed batteries or spot welder (imho).
Right now i am building a 2s battery pack for an old streamlight stinger. Im using two sanyo ga’s. If i had some of this solder on hand i would probably give it a try; soldering a tab to join the two. I have a homemade spotwelder and have built a couple tool packs with it. However, i also used it to build a cordless phone battery pack out of aaa enloops and i left it on a little too long and the cell decided to heat up. I threw the cell outside as it continued to heat up. Come to think about it, its still out there! I forgot about that! Anyway, i am now a bit timid with the spot welder until i get an appropriate control circuit. Right now my control circiut is a capacitor on the gate of the relay. Not the best design for a spot welder delay!
So what can you do with Rose’s metal what you can not do with normal solder? I can make perfect solder joints on top of batteries with common solder, with the added security of the higher melting point. And I would feel more safe even if the joints are spotwelded.
Ya i suppose. I made a drill pack that way. I used 30qs. The pack has been a lot of trouble. The cell voltages will not balance out. I assumed it was because a couple cells got over heated when i soldered them. But this is just an assumption. I dont really know for sure. I would be more comfortable heating a cell tab to 90 over 180 though.
