The Unreasonable Power Density Of Lithium-Ion

March 21, 2026 by Elliot Williams 67 Comments

We’re all used to it by now, but I’d just like to reflect on how insanely power-packed lithium ion batteries are, and everything that’s afforded us. I’m trying to think of a gadget, a hobby, or nearly anything in my house that’s not touched by the battery chemistry.

I’m looking at my portable wireless keyboard in front of me, with a LiPo pack inside. Oddly enough, I’m charging it with a LiPo-based power bank, simply because the cable to the nearest USB-C adapter is too short. A gaming console, cell phone, and a DSLR camera are all within arms reach and powered with lithium.

It’s not just consumer stuff either. I fly FPV quads and airplanes for fun when I can, and of course those are made entirely possible by the combination of smaller brushless DC motors and their drivers, and the high-power-density LiPo packs that power them. For field recharging, I have a huge self-made LiIon pack that can keep them all in the air all day. These days, LiPo and LiIon tech is the heart of hacker projects big and small. Heck, we even powered this year’s Hackaday Supercon badge with a LiPo that allowed it to run all weekend on a charge for many folks, where in the past swapping out AAs during the event was commonplace.

The application that still blows my mind is that we recently got a solar installation on our roof, which means a huge LiFePO battery in the basement. And while it’s one thing to power noisy little quads on the battery tech, it somehow seems another to power our entire house, for multiple hours per day, from a battery. Granted it’s not a couple of AAA cells in a little black plastic box, but it’s simply amazing to run a washing machine, the fridge, the stove, and even the heating off of what amounts to a battery pack.

Of course, I’m aware of the costs of producing the cells, both in terms of money and the environmental damage. It’s not a free lunch, and I’m looking forward to both cleaner and cheaper energy storage chemistries in the future. But for now, I’m still in awe of the many options that lithium-based battery chemistry has brought us. May your pillows remain non-spicy!

Lumafield Shows Why Your Cheap 18650 Cells Are Terrible

September 29, 2025 by Jenny List 40 Comments

Lithium-ion cells deliver very high energy densities compared to many other battery technologies, but they bring with them a danger of fire or explosion if they are misused. We’re mostly aware of the battery conditioning requirements to ensure cells stay in a safe condition, but how much do we know about the construction of the cells as a factor? [Lumafield] is an industrial imaging company, and to demonstrate their expertise, they’ve subjected a large number of 18650 cells from different brands to a CT scan.

The construction of an 18650 sees the various layers of the cell rolled up in a spiral inside the metal tube that makes up the cell body. The construction of this “jellyroll” is key to the quality of the cell. [Lumafield’s] conclusions go into detail over the various inconsistencies in this spiral, which can result in cell failure. It’s important that the edges of the spiral be straight and that there is no electrode overhang. Perhaps unsurprisingly, they find that cheap no-name cells are poorly constructed and more likely to fail, but it’s also interesting to note that these low-quality cells also have fewer layers in their spiral.

We hope that none of you see more of the inside of a cell in real life than you have to, as they’re best left alone, but this report certainly sheds some light as to what’s going on inside a cell. Of course, even the best cells can still be dangerous without protection.

Making The World’s Smallest E-Bike Battery

September 1, 2025 by Fenix Guthrie 25 Comments

Often times, e-bikes seek to build the biggest battery with the most range. But what if you want to take a couple lunch loops on your bike and only need 20 minutes of charge? That’s [Seth] from Berm Peak set out to find out with his minuscule Bermacell battery.

The battery is made from only 14 18650s, this tiny 52V batty is nearly as small an e-bike battery as can be made. Each cell is 3000 mAh making a total battery capacity of 156 Wh. All the cells were welded in series with an off the shelf BMS and everything was neatly packaged in an over-sized 3D printed 9V battery case. [Seth] plans to make another smaller battery with less then 100 Wh of capacity so he can take it on a plane, so stay tuned for more coverage!

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Save Cells From The Landfill, Get A Power Bank For Your Troubles

April 27, 2025 by Donald Papp 36 Comments

A hefty portable power bank is a handy thing to DIY, but one needs to get their hands on a number of matching lithium-ion cells to make it happen. [Chris Doel] points out an easy solution: salvage them from disposable vapes and build a solid 35-cell power bank. Single use devices? Not on his watch!

[Chris] has made it his mission to build useful things like power banks out of cells harvested from disposable vapes. He finds them — hundreds of them — on the ground or in bins (especially after events like music festivals) but has also found that vape shops are more than happy to hand them over if asked. Extracting usable cells is most of the work, and [Chris] has refined safely doing so into an art.

Disposable vapes are in all shapes and sizes, but cells inside are fairly similar.

Many different vapes use the same cell types on the inside, and once one has 35 identical cells in healthy condition it’s just a matter of using a compatible 3D-printed enclosure with two PCBs to connect the cells, and a pre-made board handles the power bank functionality, including recharging.

We’d like to highlight a few design features that strike us as interesting. One is the three little bendy “wings” that cradle each cell, ensuring cells are centered and held snugly even if they aren’t exactly the right size. Another is the use of spring terminals to avoid the need to solder to individual cells. The PCBs themselves also double as cell balancers, providing a way to passively balance all 35 cells and ensure they are at the same voltage level during initial construction. After the cells are confirmed to be balanced, a solder jumper near each terminal is closed to bypass that functionality for final assembly.

The result is a hefty power bank that can power just about anything, and maybe the best part is that it can be opened and individual cells swapped out as they reach the end of their useful life. With an estimated 260 million disposable vapes thrown in the trash every year in the UK alone, each one containing a rechargeable lithium-ion cell, there’s no shortage of cells for an enterprising hacker willing to put in a bit of work.

Power banks not your thing? [Chris] has also created a DIY e-bike battery using salvaged cells, and that’s a money saver right there.

Learn all about it in the video, embedded below. And if you find yourself curious about what exactly goes on in a lithium-ion battery, let our own Arya Voronova tell you all about it.

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Playing Around With The MH-CD42 Charger Board

December 27, 2024 by Tom Nardi 12 Comments

If you’ve ever worked with adding lithium-ion batteries to one of your projects, you’ve likely spent some quality time with a TP4056. Whether you implemented the circuit yourself, or took the easy way out and picked up one of the dirt cheap modules available online, the battery management IC is simple to work with and gets the job done.

But there’s always room for improvement. In a recent video, [Det] and [Rich] from Learn Electronics Repair go over using a more modern battery management board that’s sold online as the MH-CD42. This board, which is generally based on a clone of the IP5306, seems intended for USB battery banks — but as it so happens, plenty of projects that makers and hardware hackers work on have very similar requirements.

So not only will the MH-CD42 charge your lithium-ion cells when given a nominal USB input voltage (4.5 – 5 VDC), it will also provide essential protections for the battery. That means looking out for short circuits, over-charge, and over-discharge conditions. It can charge at up to 2 A (up from 1 A on the TP4056), and includes a handy LED “battery gauge” on the board. But perhaps best of all for our purposes, it includes the necessary circuitry to boost the output from the battery up to 5 V.

If there’s a downside to this board, it’s that it has an automatic cut-off for when it thinks you’ve finished using it; a feature inherited from its USB battery bank origins. In practice, that means this board might not be the right choice for projects that aren’t drawing more than a hundred milliamps or so.

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Single Crystal Electrode Lithium Ion Batteries Last A Long Time

December 16, 2024 by Al Williams 80 Comments

Researchers have been testing a new type of lithium ion battery that uses single-crystal electrodes. Over several years, they’ve found that the technology could keep 80% of its capacity after 20,000 charge and discharge cycles. For reference, a conventional cell reaches 80% after about 2,400 cycles.

The researchers say that the number of cycles would be equivalent to driving about 8 million kilometers in an electric vehicle. This is within striking distance of having the battery last longer than the other parts of the vehicle. The researchers employed synchrotron x-ray diffraction to study the wear on the electrodes. One interesting result is that after use, the single-crystal electrode showed very little degradation. According to reports, the batteries are already in production and they expect to see them used more often in the near future.

The technology shows promise, too, for other demanding battery applications like grid storage. Of course, better batteries are always welcome, although it is hard to tell which new technologies will catch on and which will be forgotten.

There are many researchers working on making better batteries. Even AI is getting into the act.

Hardware Reuse: The PMG001 Integrated Power Management Module

August 27, 2024 by Dave Rowntree 15 Comments

Battery management is a tedious but necessary problem that becomes more of a hassle with lithium-ion technology. As we’re all very aware, such batteries need a bit of care to be utilized safely, and as such, a huge plethora of ICs are available to perform the relevant duties. Hackaday.IO user [Erik] clearly spent some time dropping down the same old set of ICs to manage a battery in their applications, so they created a drop-in castellated PCB to manage all this.

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