Attack Of The Flying 18650s

March 3, 2021 by 31 Comments

When somebody builds a quadcopter with the express purpose of flying it as fast and aggressively as possible, it’s not exactly a surprise when they eventually run it into an immovable object hard enough to break something. In fact, it’s more like a rite of passage. Which is why many serious fliers will have a 3D printer at home to rapidly run off replacement parts.

Avid first person view (FPV) flier [David Cledon] has taken this concept to its ultimate extreme by designing a 3D printable quadcopter that’s little more than an 18650 cell with some motors attached. Since the two-piece frame can be produced on a standard desktop 3D printer in a little over two hours with less than $1 USD of filament, crashes promise to be far less stressful. Spend a few hours during the week printing out frames, and you’ll have plenty to destroy for the weekend.

While [David] says the overall performance of this diminutive quadcopter isn’t exactly stellar, we think the 10 minutes of flight time he’s reporting on a single 18650 battery is more than respectable. While there’s still considerable expense in the radio and video gear, this design looks like it could be an exceptionally affordable way to get into FPV flying.

Of course, the argument could be made that such a wispy quadcopter is more likely to be obliterated on impact than something larger and commercially produced. There’s also a decent amount of close-quarters soldering involved given the cramped nature of the frame. So while the total cost of building one of these birds might be appealing to the newbie, it’s probably a project best left to those who’ve clocked a few hours in on the sticks.

We’ve seen quite a few 3D printed quadcopter frames over the years, but certainly none as elegant as what [David] has created here. It’s an experiment in minimalism that really embraces the possibilities afforded by low-cost desktop 3D printing, and we wouldn’t be surprised to see it become the standard by which future designs are measured.

Handy Tool Drains 18650 Cells So You Don’t Have To

February 1, 2021 by 29 Comments

Draining a battery is easy. Just put a load across the terminals, maybe an incandescent bulb or a beefy power resistor, and wait. What’s quite a bit trickier is doing so safely. Put too large a load on, or leave it connected for longer than necessary, and you can end up doing damage to the cell. Not convinced he’d always remember to pull the battery out of his jury-rigged discharger at the opportune moment, [Jasper Sikken] decided to come up with a simple tool that could automatically handle the process with the cold and calculating precision of silicon.

V4 used the protection module from a pouch battery.

At a glance we can see the major components you’d expect in a discharger: a fairly simple PCB, four ceramic power resistors, a holder for a single 18650 cell, and a rocker switch to connect it all together. But wait, what’s that a TP4056 charging module doing in there?

While its presence technically makes this device a battery charger, [Jasper] is actually using it for the onboard protection IC. With the charging module between the cell and the power resistors, it will cut the connection when the voltage drops to 2.4 V. Oh yeah, and it can charge the battery back up if you connect up a USB cable.

[Jasper] says his little tool works great, with the resistor array putting just enough load on the battery to pull it down quickly without getting so hot that they’re dangerous to have exposed. He estimates the BOM for this gadget runs around $2 USD, and is considering offering it as a kit on Tindie in the near future.

If you’re looking for something a bit more advanced, [Jasper] built a programmable load a few years back that can discharge batteries and test power supplies all while logging the data to your computer for later analysis.

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Building A Cell Testing Station For 18650s

September 21, 2020 by 34 Comments

The 18650 is perhaps the world’s favorite lithium battery, even if electric car manufacturers are beginning to move towards larger cells such as the 21700. Used heavily in laptops and flashlights, it packs a useful amount of energy into a compact, easy to use package. There’s a small industry that has developed around harvesting these cells from old equipment and repurposing them, and [MakerMan] wanted to a piece of the action. Thus, he created a cell testing station to help in the effort.

Make no mistake, this is not a grandiose smart cell tester with 40 slots that logs every last iota of data into a cloud spreadsheet for further analysis. Nope, this is good old fashioned batch processing. [MakerMan] designed a single PCB that replicates the same cell testing circuit four times. Since PCB houses generally have a minimum order quantity of ten units, [MakerMan] ended up with forty individual cell testers on ten PCBs. Once populated, the boards were installed on a wooden frame with an ATX power supply which supplies the juice to run the system.

Overall, it’s a quick, cheap way for capacity testing cells en masse that should serve [MakerMan] well. We look forward to seeing where these cells end up. We’ve seen his work before, too – with a self-built laser engraver a particular highlight. Video after the break.

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A Modular System For Building Heavy Duty 18650 Battery Packs

December 13, 2019 by 42 Comments

With 18650 cells as cheap and plentiful as they are, you’d think building your own custom battery packs would be simple. Unfortunately, soldering the cells is tricky, and not everyone is willing to invest in a spot welding setup just to put the tabs on them. Of course that’s only half the battle, you’ll still want some battery protection and management onboard to protect the cells.

The lack of a good open source system for pulling all this together is why [Timothy Economu] created DKblock. Developed over the last three years, his open source system allows users to assemble large 18650 battery packs for electric vehicles or home energy storage, complete with integrated intelligent management and protection systems. Perhaps best of all there’s no welding required, the packs simply get bolted together.

Each block of batteries is assembled using screws and standoffs in conjunction with ABS plastic cell holders. A PCB is placed on each side of the stack, and with tabs not unlike what you’d see in a traditional battery compartment, all the cells get connected without having to solder or weld anything to them. This allows for the rapid assembly of battery packs from 7.2 VDC all the way up to 150 VDC , and means individual cells can easily be checked and replaced in the future should the need arise.

For monitoring the cells, a “Block Manager” board is installed on each block, which communicates wirelessly to a “Pack Supervisor” board that monitors the overall health of the system. Obviously, such a robust system is probably a bit overkill if you’re just looking to build a pack for your quadcopter, but if you’re looking to build a DIY Powerwall or juice up a custom electric vehicle, this could be the battery management system you’ve been looking for.

An Exhaustive Guide To Building 18650 Packs

June 12, 2019 by 23 Comments

Most of us know the basics of building packs of lithium-ion batteries. We’re familiar with cell balancing and the need for protection circuitry, and we understand the intricacies of the various serial and parallel configurations. It’s still a process that can be daunting for the first-time pack-builder though, because the other thing that most of us know about lithium ion batteries is that getting things wrong can cause fires. Rule zero of hackerspaces is “Don’t be on fire”, so what’s to be done? Fortunately [Adam Bender] is on hand with an extremely comprehensive two-part guide to designing and building lithium-ion battery packs from cylindrical 18650 cells. (Edit 2025: re-linked through Internet Archive.)

In one sense we think the two-parter is in the wrong order. Part two takes us through all the technical details and theory, from lithium-ion chemistry to battery management systems and spot-welding nickel busbars, while part one shows us the construction of his battery pack. There are also a couple of videos, which we’ve placed below the break. It’s still not a job for the faint-hearted, but we’d say he’s produced about as professional and safe a pack as possible.

If spot welding worries you then it might be possible to build a pack without it. But it’s always worth considering: would you be better served buying one?

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Prototype Sodium Ion Batteries In 18650 Cells

December 2, 2015 by 70 Comments

French researchers have announced a prototype of an 18650 sodium-ion battery. If you’ve bought a powerful LED flashlight, a rechargeable battery pack, or a–ahem–stronger than usual LASER pointer, you’ve probably run into 18650 batteries. You often find these inside laptop batteries and –famously– the Tesla electric vehicle runs on a few thousand of these cells. The number might seem like a strange choice, but it maps to the cell size (18 mm in diameter and 65 mm long).

The batteries usually use lithium-ion technology. However, lithium isn’t the only possible choice for rechargeable cells. Lithium has a lot of advantages. It has a high working voltage, and it is lightweight. It does, however, have one major disadvantage: it is a relatively rare element. It is possible to make sodium-ion batteries, although there are some design tradeoffs. But sodium is much more abundant than lithium, which makes up about 0.06% of the Earth’s crust compared to sodium’s 2.6%). Better still, sea water is full of sodium chloride (which we call salt) that you can use to create sodium.

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Maglite 18650 Battery Conversion

November 28, 2013 by 30 Comments

maglite 18650

Maglite’s used(?) to be the king of flashlights, but replacing those pesky D-cell batteries is kind of ridiculous in this day and age. So [Travis] decided to upgrade it to make use of the ever-so-common, 18650 lithium-ion battery.

Not looking to purchase any components [Travis] performed this hack using simple recycled household parts. You could solder tabs on the 18650’s so they better mimic a typical alkaline battery cell, but [Travis] notes that because most solder tarnishes the electrical conductivity isn’t always the greatest. So instead, he used aluminum foil. It doesn’t look professional, but it does the job and keeps all the components unmodified so the lithium cells can be used elsewhere if needed. To center the batteries inside the Maglite he used a few strips of cardboard from a case of beer — again, this is just making use of what was available. That being said however, if you wanted to do a professional job on it, nothing is stopping you! A 3D printed 18650 to D-cell adapter would look quite nice… Finally, in order to make the battery spring contact the smaller surface area of the lithium cells, all you have to do is flip it around backwards and slightly bend the inner spring out. That’s about it.

It’s a pretty simple hack we admit, but definitely super handy. In a past project [Travis] also replaced the halogen bulb with a high power LED, making this flashlight even more powerful — and because the LED driver accepts a broader range of voltages it lasts longer too. If you need more inspiration for retrofitting flashlights with LEDs check out this switch-mode driver board hack.

Unfortunately this hack does reduce the Maglite’s thief-head-bashing-ability with such light batteries.