Everyone needs a bench power supply, and rolling your own has almost become a rite of passage for hackers. For a long time, the platform of choice for such builds seemed to be the ATX power supply from a computer. While we certainly still see those builds, a lot of the action has switched to those cheap eBay programmable DC-DC converters, with their particolored digital displays.
This hybrid bench and portable power supply is a good example of what can be accomplished with these modules, and looks like it might turn out to be a handy tool. [Luke] centered his build around the DPS3003, a constant current and constant voltage buck converter that can take up to 40-VDC input and outputs up to 32 volts at 3 amps. In bench mode, the programmable module is fed from a mains-powered 24-volt switching supply. For portable work, an 18-volt battery from a Makita drill slips into a 3D-printed adapter on the top of the case. The printed part contains a commercial terminal [Luke] scored on eBay, but we’d bet the entire thing could be 3D printed. And no problem if you change power tool brands — just print another adapter.
At some point, cleaning out the spare parts bin — or cabinet, or garage — becomes a necessity. This is dangerous because it can induce many more project ideas and completely negate the original purpose. [Chaotic Mind], considering the pile of batteries he’s collected over the past decade, decided that instead of throwing them out, he would recycle them into a grotesque USB power bank.
Inside the bulk of this power bank are an eye-popping 64 18650 Lithium Ion cells, mostly collected from laptop batteries, and wired in a parallel 8×8 pattern with an estimated capacity of over 100,000mAh(!!). The gatekeeper to all this stored energy is a two-USB power bank charger board from Tindie.
Ah — but how to package all this power? The handy man’s secret weapon: duct-tape!
To describe the constraints on developing consumer battery technology as ‘challenging’ is an enormous understatement. The ideal rechargeable battery has conflicting properties – it has to store large amounts of energy, safely release or absorb large amounts of it on demand, and must be unable to release that energy upon failure. It also has to be cheap, nontoxic, lightweight, and scalable.
As a result, consumer battery technologies represent a compromise between competing goals. Modern rechargeable lithium batteries are no exception, although overall they are a marvel of engineering. Mobile technology would not be anywhere near as good as it is today without them. We’re not saying you cannot have cellphones based on lead-acid batteries (in fact the Motorola 2600 ‘Bag Phone’ was one), but you had better have large pockets. Also a stout belt or… some type of harness? It turns out lead is heavy.
Rechargeable lithium cells have evolved tremendously over the years since their commercial release in 1991. Early on in their development, small grains plated with lithium metal were used, which had several disadvantages including loss of cell capacity over time, internal short circuits, and fairly high levels of heat generation. To solve these problems, there were two main approaches: the use of polymer electrolytes, and the use of graphite electrodes to contain the lithium ions rather than use lithium metal. From these two approaches, lithium-ion (Li-ion) and lithium-polymer (Li-Po) cells were developed (Vincent, 2009, p. 163). Since then, many different chemistries have been developed.
Just a few short years ago, it was possible to find scrapped lithium batteries for free, or at least for very cheap. What most people at the time didn’t realize is that a battery with multiple cells might go bad because only one cell is bad, leaving the others ready for salvaging. Now it’s not a secret anymore, but if you can manage to get your hands on some there’s a lot of options for use. [ijsf] took a step further with this hack, taking a few cells from a Panasonic battery and wrangling them into a MagSafe-capable power bank for a Mac.
The real hack wasn’t scavenging batteries, however, it was getting the MagSafe to signal the computer to use power from the battery bank to run the computer only, and not to use any of that energy for charging the computer’s internal batteries. This is achieved by disabling the center MagSafe pin, which is the computer’s communication line to the power adapter. After that, the battery bank could be programmed to behave properly (a feat in itself for lithium batteries) and the power bank was successfully put into operation.
Not only was this hack a great guide for how to repurpose cells from a “dead” battery, it’s also an unparalleled quick reference for any work that might need a MagSafe connector. Of course, if you’re going to work with these chargers, make sure that you’re using one that isn’t a cheap clone.
Looks like electric longboards are becoming a thing, with increasingly complex electronics going into them to squeeze as much performance as possible out of them. When an electric longboard lasts for 35 miles, can longboard hypermiling be far behind?
If endurance longboarding sounds familiar, it’s because we just covered a 25-mile electric that outlasted its rider. To get the extra 10 miles, [Andrew] cheated a little, with a backpack full of extra batteries powering his modified Boosted Board, a commercially available electric longboard. But the backpack battery was only a prototype, and now [Andrew] is well on his way to moving those batteries to a custom underslung enclosure on his new “Voyager” board. Eschewing balancing and monitoring circuitry in favor of getting as many batteries on board as possible, [Andrew] managed sixty 18650s in a 10S6P configuration for 37 volts at 21 Ah. He didn’t scrimp on tools, though – a commercial terminal welder connects all the battery contacts. We really like the overall fit and finish and the attention to detail; an O-ring seal on the 3D-printed enclosure is a smart choice.
Voyager isn’t quite roadworthy yet, so we hope we’ll get an update and perhaps a video when [Andrew] goes for another record.
People seem to have a love-hate relationship with Harbor Freight, and it mostly seems that they love to hate the purveyor of discount tools. This is not without cause — any number of HF tools have fallen apart in our hands. But there are some gems to be found amid the dregs and dross of your local branch of the 700-store US chain, as long as you match the tool to your needs and manage your expectations.
Now, we’d normally shy away from any electric chainsaw, especially a cordless saw, and doubly so a Harbor Freight special. But as [Professor Charles] demonstrates with his detailed and humorous teardown, the Lynxx 40-volt cordless 14″ chainsaw might be worth picking up just for harvesting parts. First there’s the battery pack, which is chock full of 18650 lithium cells. [Professor Charles] leads us on a detailed tour of the design compromises of the battery and charger and is none too impressed with either, but he clearly understands what it means to build to a price point. While [Charles] found the stock motor controller somewhat anemic, the real buried treasure in the tool is a huge brushless motor, powerful enough to “throw an 8-inch Vise Grip at you” during a (not so) locked rotor test.
The whole teardown is enlightening as to the engineering decisions that go into mass-market tools, so even if you can’t think of something to do with this motor, the article is worth a read. At $169 for the Lynxx (before the 20% coupon in your Sunday paper every week) it’s a little pricey to buy just to harvest parts, but it wouldn’t be the first HF tool to suffer that fate. We’ll bet these things will start showing up broken on the secondary market for a song, and if the [Professor]’s assessments are right, it likely won’t be the motors that fail.
Unless you’ve been living under a high voltage transformer, you’ve heard about the potential for Samsung’s latest phone, the Note7, to turn into a little pocket grenade without warning. With over 2.5 million devices in existence, it’s creating quite a headache for the company and its consumers.
They quickly tied the problem to faulty Li-ion batteries and started replacing them, while issuing a firmware update to stop charging at 60 percent capacity. But after 5 of the replacement phones caught fire, Samsung killed the Note7 completely. There is now a Total Recall on all Note7 phones and they are no longer for sale. If you have one, you are to turn it off immediately. And don’t even think about strapping it into a VR headset — Oculus no longer supports it. If needed, Samsung will even send you a fireproof box and safety gloves to return it.
It should be noted that the problem only affects 0.01% of the phones out there, so they’re not exactly going to set the world on fire. However, it has generated yet another discussion about the safety of Li-ion battery technology.
It was just a few months ago we all heard about those hoverboards that would catch fire. Those questionably-engineered (and poorly-named) toys used Li-ion batteries as well, and they were the source of the fire problem. In the wake of this you would think all companies manufacturing products with Li-ion batteries in them would be extra careful. And Samsung is no upstart in the electronics industry — this should be a solved problem for them.
Why has this happened? What is the deal with Li-ion batteries? Join me after the break to answer these questions.