16340 batteries (rechargeable version of CR123A)
What’s the “practical” maximum mAh available? I still have a few from olden days, when 650mAh was common. I think the highest I’ve seen is 850mAh (Vapcell). I’m suspecting this would be about the limit—after all, there are 18350 cells as low as 900mAh, with highest around 1500mAh.
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I imagine like thefreeman said that 3.5~3.6v is probably the ideal, in terms of minimal charge decay. I’ve found 3.8v to be fine and the cells sit at that level for a very long time. Trouble with testing this is that it’s so long to find out! If you have freedom of time, do a test. Have some cells at 3.5v and a couple at 3.8v. Note the charge on the battery (little label), with date. Then do a voltage test at 4, 6, 9, and 12 months. See what happens.
FWIW, you know those old notebook hole reinforcers? They look like flat mini peppermint lifesavers? Those are great to adhere to the positive end of 18650 cells. I write the post-charge resting voltage there, so I know which cells are the best and those that are lesser (for unimportant tasks).
If you leave lithium ion cells in a charger, and the charger is not plugged in, do the cells discharge more quickly than if they were not in the charger?
I recently ordered a heat gun. Should I get a hot plate in addition? What do you do with a hot plate?
I bought a temperature & air flow controlled heat gun during the recent sale. It is called “T12 Heat Guns OLED Digital Display Temperature Soldering Station”. I thought having a heat gun can be useful. I can think of several interesting uses for my heat gun. Heating flashlights to loosen glued threads, heat glues and stickers for easy removal, and possibly remove and reflow LEDs.
However, I heard that reflowing LEDs on MCPCB using heat guns may not be easy because MCPCB can soak up a lot of heat and LEDs can be damaged by heat. Temperature controlled hot plate seems to be an adequate tool for working on LEDs. However, I don’t think I will replace LEDs often. Many of lights I own have RGB aux leds and they are not mod friendly because of the small wires and tight spaces.
If I am not going to reflow many LEDs, what are other uses for a hot plate? Only other uses that I might have is heating cold coffee on the hot plate. The model of hot plate I have in mind is MECHANIC ET-10 hot plate. Price is not bad at 30 USD.
Yes, the mcpcb will soak up heat, as it should. Once it’s saturated then the heat output of the gun will start to be more controllable. It’s as easy as other methods as long as you have a good way to hold the board so that both hands are free (gun and tweezers/flux). It depends on the emitter, but generally yes, you want to use as low a temperature as possible to let things flow and get the job done without undue delay. Most of our white emitters are pretty tough but sometimes the domes will become soft or damaged with extended heat, so be careful not to bump them hard with tools. UV emitters are much more sensitive to heat. Most manufacturers state that their emitters should only be reflowed twice but we frequently do that another time or two and things seem well. The heat guns that are able to provide adjustable heat and adjustable flow are the best…often low air flow but still having moderate to high heat is a great combination (so you don’t blow tiny components off the board…). There’s no need to get overly precise about it but the graphic below that I borrowed from the internet is kind of a typical reflow heat profile (geared more toward hot oven work than hot plates or heat guns, but same difference for the most part). You can see that there is both a peak maximum temperature that should be avoided really, but a companion time frame at which the emitter should be able to tolerate that heat without damage…and the profile ramps up slowly (heat saturation and to avoid thermal shock) before leveling out when the solder melting temperature is reached and you can do the job…then remove the heat as soon as possible and let it cool. Usually the temperatures are just about the same for all emitters but you can always check the data sheets for an emitters specs/numbers. And again, for a heat gun and hobby work, this reflow profile is just a good guideline that we can try to emulate without precise controls. Heck, people successfully use cigarette lighters and propane torches to do this job…ok when done smartly.
Tiny tiny components are challenging by hand. The heat gun and different nozzles are what pros use for handwork with this stuff…just some flux and tweezers (and magnification if you need it) and a whole world opens up compared to trying to use an iron. But with the right techniques and iron tips (and flux flux flux) there’s still a lot that can be done without a heat gun if you have the skills. Heat guns are also fantastic for bending many plastics, gently preheating a surface for paint or glue, and drying small parts with nooks and crannies after a bath.
The hot plate could be used for other electronics work, especially with single-sided boards. Some adhesive mixing or curing, some catalyst coatings like a little heat for mixing (really niche stuff). If you were doing some solder or bending work on larger-but-small metal things then putting the item on the plate for heat saturation makes some jobs easier or for prolonged work that might be a pain in the butt with a torch or iron. And of course making your own chemistry lab experiments…ha. I’ve come to prefer a little hotplate for doing my emitters. I got the tiny Miniware version and love it…but man it’s tiny. That Mechanic’s version looks great and it’s very affordable (and probably better than many of the larger cheap versions out there for labs and such).
Thank you very much for the quality info. Looks like I would not have much use for a hot plate. I came by some youtube videos on the Miniware hotplate. I liked the idea, but they were pricy for my budget for hot plate. By the way, I recently received Miniware TS101 soldering iron. I really like compactness of their tools. It is very small so it can be easily put away inside a drawer.
I have a magic arm and a clamp (photo equipment), so holding the heat gun should not be an hard. However, I remember reading a post that heat guns should be applied from the bottom not from the top. That seems to be quite awkward to work on.
Would it be okay to put the MCPCB on silicone soldering mat and blow hot air from above? I think it would be okay if the air temperature is controlled…
Bottom or top…you can kind of decided based on the piece really. With a metal mcpcb it just makes more sense to heat from the bottom and keep a little heat away from the emitter dome/phosphor that way. If you’re using it for populated driver boards then pick the lesser of two evils just in case you melt the solder on parts that you’re not aiming for. The board for a tail spring…maybe best to use a soldering iron there but using a heat gun from the top will help keep the spring metal hot (and for switches, definitely recommend an iron there…the plastic in switches is super easy to melt accidentally, even from just an iron if you aren’t careful).
On the silicone mat…they’re great for a lot of tasks but keep in mind that they are not dissipative AT ALL like a normal grounding electronics mat. Emitters and other components can be zapped by ESD and most silicone mats can really build up a charge, but despite the data sheets the emitters and chips we use seem to be pretty robust. I don’t worry about static anymore when I use my silicone mats but if it’s particularly staticky I’ll sometimes wait for more humid weather and/or actually do a grounding strap. Lots of people just hold the mcpcb with a clip or hemostats that are held in a vise or on the table edge with some weight, then apply the heat to the bottom of the board…all in the air and no mat…that works fine although a pan/skillet/hot plate is preferred. The first several I did were just on an electric range in an old shallow sautee pan and I’d use a small piece of 1/4” aluminum plate to try and buffer the temp/speed of heating a little. Most important is to just be as gentle and quick as you can with getting the solder melted. Practice a bit with some of the solder paste you’re using just to see what heat level and how much time it takes, then you can adjust a little with heat output, fan speed, nozzle size, or distance if you feel like you need to fine tune. You don’t need to totally duplicate those ramp profiles but if you have to err then faster heating and quick work before removing heat completely is much better than allowing the heat to soak for a longer time.
It’s a trademark/brand for various kinds of plastic film. They have a LOT of them in all kinds of colors, patterns, textures. I think there are just three or four of the clear ones that flashlight folks have been using. Sometimes they help to soften a beam profile to reduce rings or color aberrations, homogenize and widen the spot a little. Reduces output a tad as you’d expect…not sure if anyone has ever tested but I’d imagine that it’s a little more than what textured plastic optics do. Boaz here and Vinh at Skylumen both make small pieces available to us for cheap, which is nice. You can buy a small roll for not too much money but it’s more than you’d use in a lifetime of flashlights, probably.
On the D-C…I’m stumped. I just looked all around and I can’t find any reference to that. It’s a German company and it looks like they’re connected with or under the giant Continental conglomerate umbrella. None of their sites I looked at gave a clue that I could find.
Thanks for the reply. I kind of figured it was some kind of diffusing product from reading the posts. The lack of info on “DC Fix” on Google makes sense now that it is some kind of brand name from a certain company.
Thank you for the detailed explanation! It helped a lot.
My heat gun was delivered a couple days ago and I was able to remove a led with ease with the heat gun. I just put the MCPCB on my silicone mat and applied 250C heat with 80% air flow and one led (four leds are installed on my MCPCB) was easily removable. However, my cheap and skinny silicone mat began deforming (balloon up) upon heating. Luckily my desk underneath the mat was not damaged and the mat went back to its original shape when I removed the heat.
My solder paste has not arrived yet, but trying to solder back the removed led using original solder and additional flux did not seem to work as well. I think removing component requires significantly lower temp than installing. So, I think I need to apply more heat. However, since hotter air can potentially damage dome or other weak part of led I think it makes much more sense to apply heat from the bottom and closely monitor the solder.
Today, a cheap hot plate ($4) I purchased was delivered. Reflowing was much quicker and easier. The cheap hot plate was able to reach over 200C (it stabilizes around 250C) in less than a minute. Using it, I was able to reinstall the previously removed led using existing solder with additional flux paste. I understood right away why using a hot plate is much easier. By the way, I had to unplug the hot plate pretty quickly because when the plate reached over 200C the reflowing was already done. I was able to check the boing (in the famous video by Matt https://www.youtube.com/watch?v=B3F68ubfBkk ) and was able to push out extra solder after the plate was unplugged. It was $4 well spent! I have also ordered a small copper block that can be attached to a soldering iron, so I think I can use that to slow down the heating. Thank you for the tip!
I wonder if Boaz might know the answer. It’s been a long time but if memory serves I think he tested all kinds of them and decided that DC was the better product for various reason, including the adhesion qualities. I have half a mind to email the company now and see if they can reveal the name origin. First guess is that the D stands for decorative or similar.
