Black and white photo of Evertop computer on desk

The Evertop: A Low-Power, Off-Grid Solar Gem

April 23, 2025 by Heidi Ulrich 22 Comments

When was the last time you saw a computer actually outlast your weekend trip – and then some? Enter the Evertop, a portable IBM XT emulator powered by an ESP32 that doesn’t just flirt with low power; it basically lives off the grid. Designed by [ericjenott], hacker with a love for old-school computing and survivalist flair, this machine emulates 1980s PCs, runs DOS, Windows 3.0, and even MINIX, and stays powered for hundreds of hours. It has a built-in solar panel and 20,000mAh of battery, basically making it an old-school dream in a new-school shell.

What makes this build truly outstanding – besides the specs – is how it survives with no access to external power. It sports a 5.83-inch e-ink display that consumes zilch when static, hardware switches to cut off unused peripherals (because why waste power on a serial port you’re not using?), and a solar panel that pulls 700mA in full sun. And you guessed it – yes, it can hibernate to disk and resume where you left off. The Evertop is a tribute to 1980s computing, and a serious tool to gain some traction at remote hacker camps.

For the full breakdown, the original post has everything from firmware details to hibernation circuitry. Whether you’re a retro purist or an off-grid prepper, the Evertop deserves a place on your bench. Check out [ericjenott]’s project on Github here.

Handheld 18650 Analyzer Scopes Out Salvaged Cells

April 3, 2025 by Tom Nardi 10 Comments

You can salvage lithium 18650 cells from all sorts of modern gadgets, from disposable vapes to cordless power tools. The tricky part, other than physically liberating them from whatever they are installed in, is figuring out if they’re worth keeping or not. Just because an 18650 cell takes a charge doesn’t necessarily mean it’s any good — it could have vastly reduced capacity, or fail under heavy load.

If you’re going to take salvaging these cells seriously, you should really invest in a charger that is capable of running some capacity tests against the cell. Or if you’re a bit more adventurous, you can build this “Battery Health Monitor” designed by [DIY GUY Chris]. Although the fact that it can only accept a single cell at a time is certainly a limitation if you’ve got a lot of batteries to go though, the fact that it’s portable and only needs a USB-C connection for power means you can take it with you on your salvaging adventures.

The key to this project is a pair of chips from Texas Instruments. The BQ27441 is a “Fuel Gauge” IC, and is able to determine an 18650’s current capacity, which can be compared to the cell’s original design capacity to come up with an estimate of its overall health. The other chip, the BQ24075, keeps an eye on all the charging parameters to make sure the cell is being topped up safely and efficiently.

With these two purpose-built chips doing a lot of the heavy lifting, it only takes a relatively simple microcontroller to tie them together and provide user feedback. In this case [DIY GUY Chris] has gone with the ATmega328P, with a pair of addressable WS2812B LED bars to show the battery’s health and charge levels. As an added bonus, if you plug the device into your computer, it will output charging statistics over the serial port.

The whole project is released under the MIT license, and everything from the STL files for the 3D printed enclosure to the MCU’s Arduino-flavored firmware is provided. If you’re looking to build one yourself, you can either follow along with the step-by-step assembly instructions, or watch the build video below. Or really treat yourself and do both — you deserve it.

If your battery salvaging operation is too large for a single-cell tester, perhaps it’s time to upgrade to this 40-slot wall mounted unit.

Continue reading “Handheld 18650 Analyzer Scopes Out Salvaged Cells” →

Integrated BMS Makes Battery Packs Easy

March 26, 2025 by Bryan Cockfield 40 Comments

[Editor’s note: The hacker requested that we remove the image for legal reasons, so it’s blurry now. We hope all’s well!]

Lithium technology has ushered in a new era of batteries with exceptionally high energy density for a reasonably low cost. This has made a lot possible that would have been unheard of even 20 years ago such as electric cars, or laptops that can run all day on a single charge. But like anything there are tradeoffs to using these batteries. They are much more complex to use than something like a lead acid battery, generally requiring a battery management system (BMS) to keep the cells in tip-top shape. Generally these are standalone systems but [CallMeC] integrated this one into the buswork for a battery pack instead.

The BMS is generally intended to make sure that slight chemical imbalances in the battery cells don’t cause the pack to wear out prematurely. They do this by maintaining an electrical connection to each cell in the battery so they can charge them individually when needed, making sure that they are all balanced with each other. This BMS has all of these connections printed onto a PCB, but also included with the PCB is the high-power bus that would normally be taken care of by bus bar or nickel strips. This reduces the complexity of assembling the battery and ensures that any time it’s hooked up to a number of cells, the BMS is instantly ready to go.

Although this specific build is meant for fairly large lithium iron phosphate batteries, this type of design could go a long way towards making quick battery packs out of cells of any type of battery chemistry that typically need a BMS system, from larger 18650 packs or perhaps even larger cells like those out of a Nissan Leaf.

Have Li-ion Batteries Gone Too Far?

March 13, 2025 by Navarre Bartz 84 Comments

The proliferation of affordable lithium batteries has made modern life convenient in a way we could only imagine in the 80s when everything was powered by squadrons of AAs, or has it? [Ian Bogost] ponders whether sticking a lithium in every new device is really the best idea.

There’s no doubt, that for some applications, lithium-based chemistries are a critically-enabling technology. NiMH-based EVs of the 1990s suffered short range and slow recharge times which made them only useful as commuter cars, but is a flashlight really better with lithium than with a replaceable cell? When household electronics are treated as disposable, and Right to Repair is only a glimmer in the eye of some legislators, a worn-out cell in a rarely-used device might destine it to the trash bin, especially for the less technically inclined.

[Bogost] decries “the misconception that rechargeables are always better,” although we wonder why his article completely fails to mention the existence of rechargeable NiMH AAs and AAAs which are loads better than their forebears in the 90s. Perhaps even more relevantly, standardized pouch and cylindrical lithium cells are available like the venerable 18650 which we know many makers prefer due to their easy-to-obtain nature. Regardless, we can certainly agree with the author that easy to source and replace batteries are few and far between in many consumer electronics these days. Perhaps new EU regulations will help?

Once you’ve selected a battery for your project, don’t forget to manage it if it’s a Li-ion cell. With great power density, comes great responsibility.

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.

Continue reading “The Coolest Batteries You’ve Never Heard Of” →

A dark warehouse contains a number of large blocky objects. A Tesla Model 3 sedan sits in the center with flames underneath and curling up the side away from the camera. A firefighter on the left side attempts to put out the fire with a fire hose.

UL Investigates The Best Way To Fight EV Fires

February 26, 2025 by Navarre Bartz 50 Comments

While electric vehicles (EVs) are generally less likely to catch fire than their internal combustion counterparts, it does still happen, and firefighters need to be ready. Accordingly, the UL Research Institute is working with reverse engineering experts Munro & Associates to characterize EV fires and find the best way to fight them.

There is currently some debate in the firefighting community over whether it’s better to try to put an EV battery fire out with water or to just let it burn. Research like this means the decision doesn’t have to fall on only anecdotal evidence. Anyone who’s worked in a lab will recognize the mix of exceedingly expensive equipment next to the borderline sketchy rigged up hacks on display, in this case the super nice thermal imagers and a “turkey burner on steroids.” The video goes through some discussion of the previous results with a Chevy Bolt, Hyundai Kona, Ford Mustang Mach E, and then we get to see them light up a Tesla Model 3. This is definitely one you shouldn’t try at home!

While the massive battery banks in modern EVs can pose unique challenges in the event of an accident, that doesn’t mean they can’t be repurposed to backup your own home.

Continue reading “UL Investigates The Best Way To Fight EV Fires” →

NEMA Releases Standard For Vehicle-to-Grid Applications

February 22, 2025 by Navarre Bartz 70 Comments

Vehicle-to-grid (V2G) has been hailed as one of the greatest advantages of electrifying transportation, but has so far remained mostly in the lab. Hoping to move things forward, the National Electrical Manufacturers Association (NEMA) has released the Electric Vehicle Supply Equipment (EVSE) Power Export Permitting Standard.

The new standards will allow vehicle manufacturers and charger (EVSE) suppliers to have a unified blueprint for sending power back and forth to the grid or the home, which has been a bit of a stumbling block so far toward adoption of a seemingly simple, but not easy, technology. As renewables make up a larger percentage of the grid, using the increasing number of EVs on the road as battery backup is a convenient solution.

While the standard will simplify the technology side of bidirectional charging, getting vehicle owners to opt into backing up the grid will depend on utilities and regulators developing attractive remuneration plans. Unfortunately, the standard itself is paywalled, but NEMA says the standard “could put money back in electric vehicle owners’ pockets by making it easier for cars to store energy at night or when turned off and then sell power back to grids at a profit during peak hours.”

We’ve covered some of the challenges and opportunities of V2G systems in the past and if you want something a little smaller scale, how about using a battery that was once in a vehicle to backup your own home?