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huhu posted:I've got a bunch of through hole diodes on a roll and I want to cut it up into 6 diodes per kit I'm making. What might be the easiest way to do this that isn't fully manual? Service? Machine you can 3d print/laser cut yourself? Etc. I think you might be quickest if you make a jig with a little guillotine or roller cutter. Make something that allows you to pull out the right length to a stop so you can just pull it to the stop each time and not have to worry about accuracy. Add a little guillotine or roller cutter to cut the tape. I'd say that way you can cut one set of diodes every few seconds. Possibly 1000 sets per hour. Boring job but unless you need thousands of kits, it may be more time efficient then doing it a fancy way with an automated feeder, a light gate counter and an automated cutter.
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Dec 13, 2020 22:23
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poeticoddity posted:I once accidentally damaged an 18650 cell in such a way that fire came out while I was holding it, so I'm Nth-ing the suggestion of, "Do your experiments outdoors," and adding "away from flammables" and "have a fire extinguisher handy". 4 words: Explosion containment pie dish. I don't screw around with lithium cells myself, but i often charge grey import/ebay/aliexpress stuff with batteries in a cookie tin.
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Jul 27, 2021 03:40
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 Wow, thanks dutch webshop, for giving me the joy of sorting out 10 different values of capacitor of which i ordered 5 or 10 per value. FFS, if you order these in China you get them neatly bagged per value. I wanted to order locally because i wanted them quickly and was hesitant to order during chinese new year. But they didn't even tape them together with a bit of sticky tape.
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Jan 27, 2023 13:47
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I don't know anymore where i bought it - probably a shop called Jukebox Revival - but i recently got some old fashioned stripboard that had the space between the tracks/strips slightly recessed. This worked a LOT better than the traditional perfectly flat type, when it comes to accidentally making solder bridges. It didn't cost anything extra. Can highly recommend. Aliexpress prototype boards (like this but much cheaper https://www.futurlec.com/protoboards/proto777.shtml) are VERY bad. Tracks lift very quickly.
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Mar 7, 2023 09:30
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Shibari for wires.
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Mar 8, 2023 17:17
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7 instead of 5 is acceptable when it's for an aux winding that gets shut off immediately after getting up to speed. If it's constantly in circuit, then the aux coil will get considerably hotter because the the AC resistance of the capacitor is a lot lower. Combined with the higher mains voltage compared to 30 years ago, it might actually burn up the motor winding. 450v AC is acceptable, as long as the capacitor is rated for the duty it's getting. If it's a starter capacitor in running capacitor duty, it'll blow up after a while. Many capacitors are run-rated these days, with an indicated 10.000 hours of service. If you can't find 5µF, 4,7µF is completely acceptable and a standard value. LimaBiker fucked around with this message at 17:54 on Mar 22, 2023 |
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Mar 22, 2023 17:29
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Oh yeah, for just a test it doesn't matter. Thermostats are pretty much universal parts, if it's dead you can just get a brand new one that might have a different shape, but otherwise functions exactly the same.
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Mar 22, 2023 18:02
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Shame Boy posted:Re: plastics, I recently figured out that PVC plasticizers are used in enormous amounts (it can be something like 60% of the entire mass!) and constantly leak out as vapor, and will react with seemingly every other kind of polymer (especially platinum-cure silicones) to turn them into molten puddles. Try and guess how I became intimately familiar with this fact. Oh. Oooooooh. Now i know why my silicone things get attacked by something even when not actually in contact with other silicone things, when they're in a drawer together with PVC things (not sketchy chinese import, just real european stuff).
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Apr 17, 2023 16:15
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horse_ebookmarklet posted:Ok so after reset I got a lot better results and everything makes some sense now, huge relief. I have a jet lighter in my tool box. I use it for two thing: heatshrink and heating up things that soak up a ton of heat. Iron in one hand, lighter in the other, let 'er rip. Don't let the flame hit your soldering iron and beware of the hot blast of gases.
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Apr 24, 2023 09:57
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Make sure no moisture can condensate on those LED panels. A small droplet of water can already wreak havoc by electrolysis.
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Jun 3, 2023 10:12
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Rosin fumes are actually a genuine danger if you solder a lot. Chronic exposure will cause asthma. Back in the day it was not a question but a given that electronics factory workers working with rosin, would eventually get asthma. Most people won't be soldering countless hours a week, so for most the risk is very low. Since i landed a job at which i solder a couple of hours a week, as well as doing it a couple hours at home, i've been using proper precautions at home and at work. Ideally you feed the fumes outdoors, but in a pinch an activated carbon filter like the one used in recirculating cooker hoods will work pretty well. At home, my air filter instantly shoots to maximum about 30 seconds after touching a bit of solder to my soldering iron. The particulates of vaporized rosin spread quickly.
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Jul 31, 2023 09:40
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It has nothing to do with the skin effect, but with the fact that your nerves and muscles do not respond to frequencies of 100khz-3MHz, the average tesla coil working frequency. Even if there's skin effect in the very imperfect conductor that is the body, you should definitely feel the current impacting all the more superficial nerve endings and nociceptors in your skin. Either way, you can get nasty burns from it. I had a little oopsie with a 15w radio transmitter's loop antenna which started to have tesla coil aspirations. Tuning cap flashed over to my finger while tuning it. Didn't feel it until things started heating up, i had a little crater in my finger tip for months.
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Aug 7, 2023 09:23
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kid sinister posted:Is that an LCD or a VFD? Because you'd have to change the phosphor inside the sealed tube if it's a VFD, vacuum it out again and finally seal the glass. No VFD. If you zoom in, you can see there is no grid in there. VFDs are also very inefficient in the red color range so they rarely made red VFDs. A new head unit in an old car looks like crap. In this case, replacing the backlight LEDs will do. It might be a bit of a project because car radios were built very compact, but it's doable.
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Aug 26, 2023 09:11
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Use a bog standard PWM lamp dimmer/motor control. There are countless of those on ali/ebay. If you wanna DIY: 
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Aug 29, 2023 07:13
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His Divine Shadow posted:A PWM seems really strange application for this to me? I want two hard settings only (and half voltage gives the right result) and absolutely no other fiddling with different light intensities. Has to follow a few hard rules and always work. Especially for LED based stuff, a buck converter will sometimes not even work because of the threshold voltage of an LED, so PWM dimming is the only option. Incandescent lights are the exception - those can always be dimmed by varying the voltage. But PWM works perfectly fine too. Using a step up system and 2 different voltages of lamp in your car is madness. You only want 1 type (as in voltage) of lamp in your system. Stepping down is sensible. Because you can use 12v standard lamps that you can buy everywhere for cheap for both bright and dim. PWM is just another efficient way of stepping down the effective power. You set the desired brightness once and then don't touch it anymore. Put some silicone goo over it if you're worried about dust intrusion. It's not gonna drift unless you use very lovely chinese trimmers. But you can just as well replace the potentiometer/trimmer with some fixed resistors. Use a switch to bridge one of the two resistors (or one half of the trimmer) and it should jump from the preset value to 100% duty cicle. I'm not completely in the know about actually designing PWM controllers with a 555, but i've used the circuit above countless times and it works very well. If it so happens to be your kink, you can also use an arduino to generate a 50% (or whatever power level you want) PWM signal and switch it to 100% via a data line. Either way, PWM is the option i'd choose because i'm used to using it. A regulator to lower the voltage will also work, though it might very well just be PWM inside without you knowing it. LimaBiker fucked around with this message at 17:04 on Aug 29, 2023 |
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Aug 29, 2023 16:57
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You need a sponge made from cellulose. Kitchen sponges are often synthetic and can melt to your tip. I think many car sponges are cellulose. Try it out - get a piece of dry sponge and hold a lighter near/against it. If the material melts it's no good. If it burns/chars without melting first, it's fine.
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Sep 2, 2023 14:30
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My experience of nicd and nimh are both in cycle use, and occasionally in 'oops i left it to self discharge to 0%' use. Ni-Cd is a lot hardier it seems. I have a bunch of AA Ni-Cds of 20 years old that are still functional, despite the 'oops left it to self discharge' moments. Ni-MH's don't last long in this type of abusive scenario. I have no 20 year old Ni-MHs and even in my stack of 5 year old D cells (that are annoyingly expensive to replace) i have like 20% failure after about 20 cycles in 5 years. They are store brand, but made in germany afaik. Ni-Cd will eventually die if you overcharge the hell of it on a daily basis. Handheld vacuum cleaners and power tools with dumb fast chargers were notorious for that. They'll tolerate overcharging at 1/10c for quite a while, but even in that case it's best to actually stop charging when they're full. If space and topping up with water is not an issue, check out nickel-iron batteries. Those were the go-to backup solution for telephone exchanges throughout the 20th century if you needed a stack of batteries that would last for decades.
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Oct 1, 2023 08:36
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If it's a small couple watt SMPS, the variac should have no issues at all driving it. Most SMPSs of today are completely happy at 110v. No guarantee that they all are - it is not impossible that you got one that's designed so cheaply that the switching transistors can't handle the extra current you need at 110v to get to the specified output voltage. Are you sure you wired the variac correctly? If you hooked up the mains to the wiper and the bottom side of the coil, and start dimming from 230v down, you start at 230v but slowly increase voltage to around 400v between the bottom and the top side of the coil, a voltage at which the LED and/or SMPS will definitely pop. The 'bottom' part of the variac's winding, that now is set for 110v but hooked up to 230v mains, is heavily overloaded because of the lower inductance, increasing the current through the winding.
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Nov 14, 2023 21:44
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Glad you figured it out and the variac survived  They're fairly robust things.
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Nov 15, 2023 10:26
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Sounds nice, but consider this: you might only need the PSU and the multimeter, and outlets are already available. But now you have to put the entire pelicase on your workbench or the improvised space you gotta work on. It is a nice idea, but i would not permanently tie everything together in the case. Rather, make it easy to remove individual parts that you need for that specific job.
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Nov 26, 2023 17:28
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babyeatingpsychopath posted:From what I remember, they use rotary converters AKA motor-generator sets. Giant transformers on the locomotives themselves to feed power to the traction motors. Smaller big motor generators to power stuff like lights, aux equipment and battery chargers on the train. If you look up videos of old 1910s-1930s german or swiss locomotives, you can hear the deep 16,7hz rumble if you have good speakers or good headphones. It's a weird, uncanny sound if you're used to standard 50hz hum being everywhere.
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Dec 16, 2023 10:27
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It also saves on very expensive 15kV suitable circuit breakers and such, if you only have 1 big honking transformer whose power you gotta interrupt. Circuit protection and switching is much easier at 1500 or 700v or whatever voltage those things used - i have no clue.
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Dec 16, 2023 18:20
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It is a bandpass filter. It consists of 2 tuned LC circuits, that are inductively coupled to each other. The impedance of it is very high for the frequency it's tuned to. Anything above and below it gets shorted to ground. The capacitor takes care of the high frequencies, the inductor of the low frequencies, together they resonate and form a sort of bell curve. It is very rare to find it in this configuration at the input (RF) side of a receiver, because generally the bandwidth of such a device is very narrow, so you would only be able to receive one single station. Instead, you find it at the IF (intermediate frequency) stages. Bandpass filters at the input stage do exist, but they always are tuned together with the oscillator circuit, to tune into the desired station.
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Dec 21, 2023 14:04
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Highly unusual and quite the hack to use one of those, non-tuned, as an input stage to any receiver. I knew vaguely similar things were used in german post-war emergency receivers, because a dual gang tuning capacitor was hard to get and/or expensive back then. Strictly spoken the one in the circuit does not have tunable slugs. There is no 'trimmer' symbol in the coils. I checked out the datasheet of the FM receiver IC and it uses the PFJB2 bandpass filter. Can't find much info about that.
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Dec 21, 2023 15:42
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A 100nF/100 ohm snubber network connected parallel to the brake light switch might help against any bursts of RF caused by the tiny spark that switch contacts can produce. If the brake lights are powered via a relay, put one over the relay switch contacts too.
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Jan 5, 2024 16:18
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They really think for the long term. Motors and generators are still available in the same form factor as they were in the 1960s, but it's reasonable to expect that the current microcontrollers won't be around anymore in 20 years time while the industry standard motors/generators will keep being industrial lego parts. They might keep boards in stock for a while, but i wouldn't be suprised if they wouldn't be able to supply boards for very old solid state converters.
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Jan 22, 2024 22:32
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Rocko Bonaparte posted:Does somebody have a recommended method for homebrew PCB's or should I just get them fab'd? Toner transfer works with solid reliability here. I use iron (3) chloride etchant just because it's always available in the lab where i work. Benefit compared to getting boards made is that you can design your board in the morning, and have the circuit board the same afternoon. When i have the design, the whole process from printing to having a finished board takes 30-45 minutes for a single sided board. Double sided is a whole other can of worms, DIY'ing via's is no fun. Quality of the board houses is almost always better than what you do yourself. But i want things quickly so i still do my own boards. LimaBiker fucked around with this message at 08:08 on Feb 14, 2024 |
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Feb 14, 2024 08:06
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It all depends on how fast you want to iterate your designs. It's really satisfying to just have a completely finished prototype in a single day. If you design a double sided board with a very limited amount of bottom traces (that will become jumper wires if you etch the board yourself, or get fabricated as normal if you order the board somewhere) you can easily try it out. The CAD stuff takes much more time than making a board. The amount of lab stuff you need is limited. My first tiny boards i did in a 500ml beaker of etchant sitting on the lab hot plate with a stir bar in it. Only recently i made an actual etching tank that fits an eurocard, from some laser cut polycarbonate. Aquarium air pump and a glass rod i blew some holes in to bubble air through it. The etching solution stays warm enough for the time needed, so it doesn't have heating. I never bothered with UV exposing transparencies, because i often only need a single board. Using the transparancies makes it easier to create larger numbers, but if you need larger numbers i'd just order them. I have also been thinking about laser ablating etch resist, since we have a laser cutter (for plastics and wood) at work. That would be absolutely fantastic. LimaBiker fucked around with this message at 18:29 on Feb 14, 2024 |
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Feb 14, 2024 18:26
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Is the little neon lamp still good, as in 'Didn't turn black due to decades of use'? Easiest thing you could try is to put a blue neon indicator in there, because it will have a better contrast with the cream/yellow strip. Runs on the same voltage/series resistor. The green ones look really nice but you need to run them very dimly at like 0,2mA or they'll wear out within a year or so. If the blue neon doesn't work well enough, get a couple of SMD leds and a random USB power supply, and hook it up with a correct series resistor.
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Mar 14, 2024 16:58
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Let the guy start out with a TV flyback or a car ignition coil. Both hurt like a motherfucker, and the voltage can be around 30kV. However, the current and power are more limited (think 1 to 4mA or so for the TV flyback, <10mA for the ignition coil). Few TV repairsmen have died from the 27kV supply, more died from hot chassis TVs that carry mains. If he can play around with one of those for a year and not get shocked a single time, then he could consider getting a bigger transformer. If he does get zapped, he is not competent enough. Either way, at the multi kV levels, things do not always categorize nicely anymore into 'conductor' and 'isolator'. Any bit of moisture in or on a surface can become a pathway for tracking, and continue to zap you. The most important thing is to realize that it's all a lottery at those high power levels. Many people have survived it with just a little crater in their finger or hand. But he can easily be the one who gets 'stuck' onto the wire and can't release until his hand has burnt through, or never at all and die the worst death you can imagine. LimaBiker fucked around with this message at 09:36 on Mar 15, 2024 |
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Mar 15, 2024 09:33
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Design it in such a way that you don't get A. electrolysis (results in rapid electrode wear) or electroplating (results sometimes in a spurious bias voltage from it working as an electrochemical cell) from the measurement current. This means using an AC voltage to feed the sensor. And B. use corrosion resistant materials. Gold plated PCB is an option. Very traditional carbon rods also hold out quite nicely. If you use a known AC measurement frequency like 1kHz you can quite nicely filter that one frequency out and avoid all 60hz + harmonics interference. LimaBiker fucked around with this message at 23:56 on Mar 22, 2024 |
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Mar 22, 2024 23:49
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Smell? Quite hard. Actual temperature? Much easier with an infrared thermometer pointed at the spot where the engine will most likely be. Thermal imaging if you wanna be real fancy.
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Mar 24, 2024 20:16
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ryanrs posted:So why are RIFA caps still being manufactured? What's so good about them to offset the large physical size, high price, and explosive failures? They lose less capacity than those DAIM or MEX x2 capacitors. So for their normal life span, their performance can be slightly better. However, by now there should be better x2 capacitors that don't lose so much capacity due to self healing. Fun fact: you can even get those Rifa/Kemet paper caps in SMD versions!
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Apr 21, 2024 20:54
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Fun fact: you can actually get brand new Rifa paper caps in SMD versions, for all your modern, miniturized smoke generating needs! https://nl.farnell.com/kemet/smp253ma4470mtv24/cap-film-suppression-4700pf-class/dp/3527162 This one's out of stock but there are others from both Rifa and Kemet.  They're actually surprisingly expensive. I want to buy a bunch and see how the newest, most modern paper caps fare. Hook them up to mains with a fast acting fuse in series and leave them for the next 1 or 2 decades to see what happens. But they're a bit too expensive just for a silly test.
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Apr 25, 2024 21:06
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A power supply never gives more than the device "asks for". That lithium cell can deliver dozens of amps, but the circuitry ensures that there will never be too high of a current flowing through the LEDs. There are exceptions - extremely dodgy AliExpress/wish/temu devices that don't have an actual charge controller for the lithium cell - but this device looks like it has some generic charge regulator IC (by looks - i haven't verified it with the datasheet) so you can hook it up to a 100a power supply and it will still be fine. The only thing i can think of, is that the power supply does not correctly switch between voltages. Measure.to verify. Also check to see if the cell isn't deep discharged. Sometimes the charger locks out in such a case.
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Apr 27, 2024 23:21
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Not necessarily. If you deep discharge a lithium cell below a certain voltage, the charger can lock out because deep discharged lithium cells can become unstable. Some chargers allow charging at a very low speed (phones usually do, they then appear not to charge but in fact do), some don't.
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May 2, 2024 18:01
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namlosh posted:As a complet novice I can attest to that… I’ve seen plenty of “dead” batteries for laptops or anything you can imagine that wouldn’t charge. Pull them apart and hookem up to a power supply and they’ll except charge, hold it and discharge just fine. I find that the actual cells (like 18650s) themselves are crazy robust… but I’m not using them very heavily at all so it may just be that they’re out of spec. And it must be explicitely stated that 'power supply' means a current and voltage limited bench/lab power supply, and you want to charge it at 1/10 or 1/20c until you reach the lower limit of a lithium cell. Also be aware that you can blow up the power supply if it's set to like 1v, and you hook up a battery up to it that delivers 3v or something. The control electronics will attempt to lower the voltage and get very confused.
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May 3, 2024 08:02
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