ice forming on surface with plus and minus pole

The Coolest Batteries You’ve Never Heard Of

March 9, 2025 by Heidi Ulrich 55 Comments

Imagine cooling your building with the same principle that kept Victorian-era icehouses stocked with lake-frozen blocks, but in modern form. That’s the idea behind ice batteries, a clever energy storage hack that’s been quietly slashing cooling costs across commercial buildings. The invention works by freezing water when energy is cheap, and using that stored cold later, they turn major power hogs (air conditioning, we’re looking at you) into more efficient, cost-effective systems.

Pioneers like Nostromo Energy and Ice Energy are refining the tech. Nostromo’s IceBrick modules pack 25 kWh of cooling capacity each, install on rooftops, and cost around $250 per kWh—about half the price of lithium-ion storage. Ice Energy’s Ice Bear 40 integrates with HVAC systems, shifting up to 95% of peak cooling demand to off-peak hours. And for homes, the Ice Bear 20 replaces traditional AC units while doubling as a thermal battery.

Unlike lithium-ion, ice batteries don’t degrade chemically – their water is endlessly reusable. Combining the technology with this hack, it’s even possible in environments where water is scarce. But the trade-off? They only store cooling energy. No frozen kilowatts for your lightbulbs, just an efficient way to handle the biggest energy drain in most buildings.

Could ice batteries help decentralize energy storage? They’re already proving their worth in high-demand areas like California and Texas. Read the full report here and let us know your thoughts in the comments.

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An image showing an original grey and blue Sony Walkman with the text "1970" below it, and an arrow pointing to the right of it at a much smaller blue Walkman with the text "2000" underneath it, and a final arrow pointing to the right to a bright orange cassette player by We Are Rewind in a man's hand with the text "now" beneath it.

Why Are Cassette And CD Players So Big Now?

March 1, 2025 by Navarre Bartz 66 Comments

The early 2000s were the halcyon days of physical media. While not as svelte as MP3 players became, why are those early 2000s machines smaller than all the new models popping up amidst the retro audio craze?

We’ve bemoaned the end of the electromechanical era before, and the Verge recently interviewed the people at We Are Rewind and Filo to get the skinny on just why these newer cassette and CD players aren’t as small as their predecessors. It turns out that all currently produced cassette players use the same mechanism with some small tweaks in materials (like metal flywheels in these higher quality models) because the engineering required to design a smaller and better sounding alternative isn’t warranted by the niche nature of the cassette resurgence.

A similar fate has befallen the laser head of CD mechanisms, which is why we don’t have those smooth, rounded players anymore. Economies of scale in the early 2000s mean that even a cheap player from that era can outperform a lot of the newer ones, although you won’t have newer features like Bluetooth to scandalize your audiophile friends. A new Minidisc player is certainly out of the question, although production of discs only ended this February.

If you’re looking to get back into cassettes, this masterclass is a good place to start. If you don’t fancy any of the players the Verge looked at, how about rolling your own incarnation with the guts from a vintage machine or just going for the aesthetic if cassettes aren’t your jam?

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Stealth AirTag Broadcasts When Moved: An Experiment

January 18, 2025 by Heidi Ulrich 43 Comments

A simple yet intriguing idea is worth sharing, even if it wasn’t a flawless success: it can inspire others. [Richard]’s experiment with a motion-powered AirTag fits this bill. Starting with our call for simple projects, [Richard] came up with a circuit that selectively powers an AirTag based on movement. His concept was to use an inertial measurement unit (IMU) and a microcontroller to switch the AirTag on only when it’s on the move, creating a stealthy and battery-efficient tracker.

The setup is minimal: an ESP32 microcontroller, an MPU-6050 IMU, a transistor, and some breadboard magic. [Richard] demonstrates the concept using a clone AirTag due to concerns about soldering leads onto a genuine one. The breadboard-powered clone chirps to life when movement is detected, but that’s where challenges arise. For one, Apple AirTags are notoriously picky about batteries—a lesson learned when Duracell’s bitter coating blocks functionality. And while the prototype works initially, an unfortunate soldering mishap sadly sends the experiment off the rails.

Despite the setbacks, this project may spark a discussion on the possibilities of DIY digital camouflage for Bluetooth trackers. By powering up only when needed, such a device avoids constant broadcasting, making it harder to detect or block. Whether for tracking stolen vehicles or low-profile uses, it’s a concept rich with potential. We talked about this back in 2022, and there’s an interesting 38C3 talk that sheds quite some light on the broadcasting protocols and standards. Continue reading “Stealth AirTag Broadcasts When Moved: An Experiment” →

New Frontiers For Nissan Leaf Motor And Battery

January 14, 2025 by Bryan Cockfield 9 Comments

Nissan started off with a massive lead in the electric vehicle industry — their Leaf was the first mass-market EV available and the highest-selling EV until 2020. But the company has begun to lag behind other automotive manufacturers and their more diverse, modern offerings. As an example, the Leaf still doesn’t have active cooling for its battery packs. On the plus side, though, these cars are pretty easy to work on and parts for them are widely available. This includes the battery pack and motor, which can be dropped in to other non-EV Nissan products like this Nissan Frontier.

For conversions using the Leaf battery pack and motor, [Paul] points out that it’s important to find the motor with the inverter and power distribution unit all integrated together, rather than sourcing them all separately since they don’t always mix-and-match well. There are several third-party parts available for getting these motors running in other applications, including a coupler to mate the motor to a transmission. However, this still needs some custom fabrication to properly attach to the Frontier’s drivetrain. With a new controller as well, the Frontier engine can be pulled, the Leaf engine dropped in, and the battery set into the bed and connected.

A followup video shows [Paul] driving his new EV down a neighborhood street, but it looks like there are still a few things to polish up before it’s ready to hit the open highway including a more robust housing for the battery. But, if donor vehicles can be found like a truck body and Leaf drivetrain components, this type of modification can be done for a surprisingly small cost. These EV batteries can also be put to work as home power banks as well.

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AA Battery Performances Tested, So Get The Most For Your Money

January 10, 2025 by Donald Papp 38 Comments

[Project Farm] has a video in which a wide variety of AA cells are analyzed and compared in terms of capacity, internal resistance, ability to deliver voltage under load, and ability to perform in sub-freezing temperatures. Alkaline, lithium, and even some mature rechargeable cells with a couple thousand cycles under their belt were all compared. There are a few interesting results that will can help you get the most from your money the next time you’re battery shopping.

The video embedded below demonstrates a set of tests that we recommend you check out, but the short version is that more expensive (non-rechargeable) lithium cells outperform their alkaline peers, especially when it comes to overall longevity, ability to perform under high-drain conditions, and low temperatures. Lithium cells also cost more, but they’re the right choice for some applications.

Some brands performed better and others worse, but outside of a couple stinkers most were more or less comparable. Price however, was not.

As for how different brands stack up against one another, many of them are more or less in the same ballpark when it comes to performance. Certainly there are better and worse performers, but outside of a couple of stinkers the rest measure up reasonably well. Another interesting finding was that among rechargeable cells that were all several years (and roughly 2,200 charge-discharge cycles) old, a good number of them still performed like new.

Probably the single most striking difference among the different cells is cost — and we’re not just talking about whether lithium versus alkaline AAs are more cost-effective in the long run. Some brands simply cost twice as much (or more!) than others with comparable performance. If you’re in a hurry, jump to [Project Farm] presenting the final ranked results at 19:45 in.

Relying on brand recognition may save you from buying complete junk, but it’s clearly not the most cost-effective way to go about buying batteries. These findings are similar to an earlier effort at wide-scale battery testing which also determined that factoring in price-per-cell was too significant to ignore.

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Cassette Tape Plays MP3s

January 6, 2025 by Bryan Cockfield 65 Comments

Cassette tapes were a major way of listening to (and recording) music througout the 1980s and 1990s and were in every hi-fi stereo, boom box, and passenger vehicle of the era. Their decline was largely as a result of improvements in CD technology and the rise of the MP3 player, and as a result we live in a world largely absent of this once-ubiquitous technology. There are still a few places where these devices crop up, and thanks to some modern technology their capabilities as a music playback device can be greatly enhanced.

The build starts, as one might expect, by disassembling the cassette and removing the magnetic tape from the plastic casing. With the interior of the cassette empty it’s capable of holding a small battery, USB-C battery charger, and a Bluetooth module. The head of an old tape deck can be wired to the audio output of the Bluetooth module and then put back in place in the housing in place of the old tape. With the cassette casing reassembled, there’s nothing left to do but pair it to a smartphone or other music-playing device and push play on the nearest tape deck.

As smartphones continue to lose their 3.5 mm headphone jacks, builds like this can keep lots of older stereos relevant and usable again, including for those of us still driving older vehicles that have functioning tape decks. Of course, if you’re driving a classic antique auto with a tape technology even older than the compact cassette, there are still a few Bluetooth-enabled options for you as well.

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A Modern Battery For A Classic Laptop

January 2, 2025 by Bryan Cockfield 12 Comments

Aside from their ability to operate fairly well in extreme temperatures, lead-acid batteries don’t have many benefits compared to more modern battery technology. They’re heavy, not particularly energy dense, have limited charge cycles, and often can’t be fully discharged without damage or greatly increased wear. With that in mind, one can imagine that a laptop that uses a battery like this would be not only extremely old but also limited by this technology. Of course, in the modern day we can do a lot to bring these retro machines up to modern standards like adding in some lithium batteries to this HP laptop.

Simply swapping the batteries in this computer won’t get the job done though, as lead-acid and lithium batteries need different circuitry in order to be safe while also getting the maximum amount of energy out. [CYUL] is using a cheap UPS module from AliExpress which comes with two 18650 cells to perform this conversion, although with a high likelihood of counterfeiting in this market, the 18650s were swapped out with two that were known to be from Samsung. The USB module also needs to be modified a bit to change the voltage output to match the needs of the HP-110Plus, and of course a modernized rebuild like this wouldn’t be complete without a USB-C port to function as the new power jack.

[CYUL] notes at the end of the build log that even without every hardware upgrade made to this computer (and ignoring its limited usefulness in the modern world) it has a limited shelf life as the BIOS won’t work past 2035. Hopefully with computers like this we’ll start seeing some firmware modifications as well that’ll let them work indefinitely into the future. For modern computers we’ll hope to avoid the similar 2038 problem by switching everything over to 64 bit systems and making other software updates as well.