Mechanisms of pulse current charging for stabilizing the cycling performance of commercial NMC/graphite LIBs. (Credit: Jia Guo et al., 2024)

Why Pulse Current Charging Lithium-Ion Batteries Extends Their Useful Lifespan

April 16, 2024 by 54 Comments

For as much capacity lithium-ion batteries have, their useful lifespan is generally measured in the hundreds of cycles. This degradation is caused by the electrodes themselves degrading, including the graphite anode in certain battery configurations fracturing. For a few years it’s been known that pulsed current (PC) charging can prevent much of this damage compared to constant current (CC) charging. The mechanism behind this was the subject of a recent research article by [Jia Guo] and colleagues as published in Advanced Energy Materials.

Raman spectra of a) as-cycled and b) surface-removed graphite anodes aged under CC and Pulse-2000 charging. FE-SEM images of the cross-sections of graphite electrodes aged with CC (c,d) and Pulse-2000 (e,f) charging. d,f) are edge-magnified images of (c,e). g) shows the micrograph and O and C element mapping of the surface of CC-aged graphite electrode. TEM images of h) fresh, i) CC, and j) Pulse-2000 aged graphite anodes. (Credit: Jia Guo et al., 2024)
Raman spectra of a) as-cycled and b) surface-removed graphite anodes aged under CC and Pulse-2000 charging. FE-SEM images of the cross-sections of graphite electrodes aged with CC (c,d) and Pulse-2000 (e,f) charging. d,f) are edge-magnified images of (c,e). g) shows the micrograph and O and C element mapping of the surface of CC-aged graphite electrode. TEM images of h) fresh, i) CC, and j) Pulse-2000 aged graphite anodes. (Credit: Jia Guo et al., 2024)

The authors examined the damage to the electrodes after multiple CC and PC cycles using Raman and X-ray absorption spectroscopy along with lifecycle measurements for CC and PC charging at 100 Hz (Pulse-100) and 2 kHz (Pulse-2000). Matching the results from the lifecycle measurements, the electrodes in the Pulse-2000 sample were in a much better state, indicating that the mechanical stress from pulse current charging is far less than that from constant current charging. A higher frequency with the PC shows increased improvements, though as noted by the authors, it’s not known yet at which frequencies diminishing returns will be observed.

The use of PC vs CC is not a new thing, with the state-of-the-art in electric vehicle battery charging technology being covered in a 2020 review article by [Xinrong Huang] and colleagues as published in Energies. A big question with the many different EV PC charging modes is what the optimum charging method is to maximize the useful lifespan of the battery pack. This also applies to lithium-metal batteries, with a 2017 research article by [Zi Li] and colleagues in Science Advances providing a molecular basis for how PC charging suppresses the formation of dendrites .

What this demonstrates quite well is that the battery chemistry itself is an important part, but the way that the cells are charged and discharged can be just as influential, with the 2 kHz PC charging in the research by [Jia Guo] and colleagues demonstrating a doubling of its cycle life over CC charging. Considering the amount of Li-ion batteries being installed in everything from smartphones and toys to cars, having these last double as long would be very beneficial.

Thanks to [Thomas Yoon] for the tip.

Retrotechtacular: The Other Kind Of Fallout Show

April 16, 2024 by 28 Comments

Thanks to the newly released Amazon Prime series, not to mention nearly 30 years as a wildly successful gaming franchise, Fallout is very much in the zeitgeist these days. But before all that, small-F fallout was on the minds of people living in countries on both sides of the Iron Curtain who would have to deal with the aftermath of a nuclear exchange.

“Uwaga! Pył promieniotwórczy“  (“Beware! Radioactive Dust”) is a 1965 Polish civil defense film from film studio Wytwórnia Filmów Oświatowych. While the Cold War turning hot was not likely to leave any corner of the planet unscathed, Poland was certainly destined to bear the early brunt of a nuclear exchange between the superpowers, and it was clear that the powers that be wanted to equip any surviving Polish people with the tools needed to deal with their sudden change in circumstances.

The film, narrated in Polish but with subtitles in English, seems mainly aimed at rural populations and is mercifully free of the details of both fallout formation and the potential effects of contact with radioactive dust, save for a couple of shots of what looks like a pretty mild case of cutaneous radiation syndrome.

Defense against fallout seems focused on not inhaling radioactive dust with either respirators or expedient facemasks, and keeping particles outside the house by wearing raincoats and boots, which can be easily cleaned with water. The fact that nowhere in the film is it mentioned that getting fallout on your clothes or in your lungs could be largely avoided by not going outside is telling; farmers really can’t keep things running from the basement.

A lot of time in this brief film is dedicated to preventing food and water from becoming contaminated, and cleaning it off if it does happen to get exposed. We thought the little tin enclosures over the wells were quite clever, as were the ways to transfer water from the well to the house without picking up any contamination. The pros and cons of different foods are covered too — basically, canned foods dobry, boxed foods zły. So, thumbs up for Cram, but you might want to skip the YumYum deviled eggs.

Dealing with the potential for a nuclear apocalypse is necessarily an unpleasant subject, and it’s easy to dismiss the advice of the filmmakers as quaint and outdated, or just an attempt to give the Polish people a sense of false hope. And that may well be, but then again, giving people solid, practical steps they can take will at least give them some agency, and that’s rarely a bad thing.

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Alternate Threaded Inserts For 3D Prints

April 15, 2024 by 21 Comments

The usual way to put a durable threaded interface into a 3D print is to use a heat-set insert, but what about other options? [Thomas Sanladerer] evaluates a variety of different threaded inserts, none of which are actually made with 3D printing in mind but are useful nevertheless.

There are a number of other easily-available threaded inserts, including the rivnut (or rivet nut), chunky hex socket threaded inserts intended for wood and furniture, heli-coils or helical inserts (which resemble springs), self-tapping threaded inserts (also sold as thread adapters), and T-nuts or prong nuts. They all are a bit different, but he measures each one and gives a thorough rundown on how they perform, as well as offering his thoughts on what works best.

[Thomas] only tests M5 fasteners in this video, so keep that in mind if you get ideas and go shopping for new hardware. Some of the tested inserts aren’t commonly available in smaller sizes. Self-tapping threaded inserts, for example, are available all the way down to M2, but the hex socket threaded inserts don’t seem to come any smaller than M4.

These threaded inserts might be just what your next project calls for, so keep them in mind. Heat-set inserts are of course still a great option, and our own Sonya Vasquez can tell you everything you need to know about installing heat-set inserts into 3D printed parts in a way that leaves them looking super professional.

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Building A Tape Echo In A Coke Can Tape Player That Doesn’t Really Work

April 15, 2024 by 6 Comments

Back in the 1990s, you could get a tape player shaped like a can of Coca Cola. [Simon the Magpie] scored one of these decks and decided to turn it into a tape echo effect instead. It didn’t work so well, but the concept is a compelling one. You can see the result in the video below.

The core of the effect is a tape loop, which [Simon] set up to loop around a pair of hacked-up cassette shells. This allows him to place one half of the loop in the Coca-Cola cassette player and the other half in a more conventional desktop tape deck. A 3D-printed bracket allows the two decks and the tape loop to be assembled into one complete unit.

The function is simple. The desktop tape deck records onto the loop, with the Coca-Cola unit then playing back that section of tape a short while later. Hey, presto — it’s a tape delay! It’s super lo-fi, though, and the tape loop is incredibly fragile.

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Compaq Portable III Is More Than Meets The Eye

April 15, 2024 by 8 Comments

The Compaq Portable III hails from the 386 era — in the days before the laptop form factor was what we know today. It’s got a bit of an odd design, but a compelling one, and the keyboard is pretty nifty, too. [r0r0] found one of these old-school machines and decided it was well worth refitting it to give it some modern grunt.

The Portable III ended up scoring a mini-ITX build, with an AMD Ryzen 7 3700X and an AMD RX580 GPU. Cramming all this into the original shell took some work, like using a vertical riser to fit in the GPU. Hilariously, the RGB RAM sticks are a little bit wasted when the enclosure is closed.

For the purists out there, you’ll be relieved to know the machine’s original plasma display was dead. Thus, a larger modern LCD was fitted instead. However, [r0r0] did play around with software to emulate the plasma look just for fun.

It’s funny to think you could once score one of these proud machines for free at a swap meet.

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Plasma Cutter On The Cheap Reviewed

April 15, 2024 by 24 Comments

If you have a well-equipped shop, it isn’t unusual to have a welder. Stick welders have become a commodity and even some that use shield gas are cheap if you don’t count buying the bottle of gas. But plasma cutters are still a bit pricey. Can you get one from China for under $300? Yes. Do you want one that cheap? [Metal Massacre Fab Shop] answers that question in the video below.

First impressions count, and having plasma misspelled on the unit (plasme) isn’t promising. The instructions were unclear, and some of the fittings didn’t make him happy, so he replaced them with some he had on hand. He also added some pipe tape to stop any leaking.

The first test was a piece of quarter-inch steel at 35 amps. The machine itself is rated to 50 amps. Sparks ensued, and with a little boost in amperage, it made a fair-looking cut. At 50 amps, it was time to try a thicker workpiece. It made the cut, although it wasn’t beautiful. The leaking regulator and the fact that he can’t run the compressor simultaneously as the cutter didn’t help.

From the look of it, for light duty, this would be workable with a little practice and maybe some new fittings. Unsurprisingly, it probably isn’t as capable as a professional unit. Still could be very handy to have.

It is possible to convert a welder into a plasma cutter. A handheld unit like this probably won’t benefit from a Sharpie.

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3D Printing A Cassette Is Good Retro Fun

April 15, 2024 by 9 Comments

The cassette is one of the coolest music formats ever, in that you could chuck them about with abandon and they’d usually still work. [Chris Borge] recently decided to see if he could recreate these plastic audio packages himself, with great success.

He kicked off his project by printing some examples of an open source cassette model he found online. The model was nicely accurate to the original Compact Cassette design, but wasn’t exactly optimized for 3D printing. It required a great deal of support material and wasn’t easy to customize.

[Chris] ended up splitting the model into multiple components, which could then be assembled with glue later. He then set about customizing the cassette shells with Minecraft artwork. Details of the artwork are baked into the model at varying heights just 1/10th of the total layer height. This makes it easy to designate which sections should be printed with which filament during his multi-colored print. And yet, because the height difference is below a full layer height, the details all end up on the same layer to avoid any ugly gaps between the sections. From there, it’s a simple matter of transferring over the mechanical parts from an existing cassette tape to make the final thing work.

It’s a neat trick, and the final results are impressive. [Chris] was able to create multicolored cassettes that look great. It’s one of the better uses we’ve seen for a multi-colored printer. This would be an epic way to customize a mixtape for a friend!

We’ve seen some great 3D printed cassettes before, too, like these retro reel-to-reel lookalikes.

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