Power Stacker, A Modular Battery Bank

Many of us will own a lithium-ion power pack or two, usually a brick containing a few 18650 cylindrical cells and a 5 V converter for USB charging a cellphone. They’re an extremely useful item to have in your carry-around, for a bit of extra battery life when your day’s Hackaday reading has provided a worthy use for most of your charge. These pack are though by their very nature inflexible, no matter how many cells you own, the pack will only ever contain the number with which it was shipped. Worse, when those cells are discharged or even  reach the end of their lives, they can’t be swapped for fresh ones. [Isaacporras] has a solution for these problems which he calls the Power Stacker, a modular battery pack system.

At its heart is the Maxim MAX8903 lithium-ion charge controller chip, of which one is provided for each cell. A single cell and MAX8903 with a DC to DC converter for 5 V output makes for the simplest configuration, and he has a backplane allowing multiple boards to be connected and sharing the same charge and output buses.

An infinitely configurable battery bank sounds great. It’s looking for crowdfunding backing, and for that it has an explanatory video which you can see below. Meanwhile if you’d  like to try for yourself you can find the necessary files on the hackaday.io page linked above.

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Save An Old Drill From Landfill, With Some Lithium-Ion Magic

What do you do, when your trusty cordless drill starts to lose battery capacity? You bought it a decade ago and parts are a distant memory, so there’s no chance of buying a new pack. If you are [Danilo Larizza], you strip away the old NiMh cells, and replace them with a custom pack (Italian, Google Translate link) made from 18650 Li-ion cells.

The build is a straightforward one to anyone familiar with lithium-ion packs, but to a battery newbie it should serve as a handy step-by-step description. He starts by selecting a range of matched cells from discarded laptop batteries and adds an off-the-shelf battery management board to keep everything safe. Interestingly he appears to have soldered his wires to the cells rather than the more usual spot-welding, sadly for many of us a spot-welder is beyond our means. It would be interesting to know both the mechanical integrity of the resulting connection and whether the heat of soldering might in some way affect the cells.

Firing up the drill with the new pack is not the immediate success he hoped it would be, the start-up current is so high that the battery management board goes into a fault condition. This situation is resolved with a model that can take more current, and he can take his drill out once more.

If you are annoyed by the rise of cordless tools, you’re in good company. Meanwhile if you lack a spot-welder for batteries, have a look at one of the nicer ones we’ve seen.

[GreatScott] Tests His DIY Battery Pack On His E-Bike

[GreatScott] has now joined the ranks of Electric Bike users. Or has he? We previously covered how he made his own lithium-ion battery pack to see if doing so would be cheaper than buying a commercially made one. But while it powered his E-bike conversion kit on his benchtop, turning the motor while the wheel was mounted in a vice, that’s no substitution for a real-world test with him on a bike on the road.

Since then he’s designed and 3D printed an enclosure for his DIY battery pack and mounted it on his bike along with most of the rest of his E-bike kit. He couldn’t use the kit’s brake levers since his existing brake levers and gear-shift system share an enclosure. There also weren’t enough instructions in the kit for him to mount the pedal assistance system. But he had enough to do some road testing.

Based on a GPS tracker app on his phone, his top speed was 43 km/h (27 miles per hour). His DIY 5 Ah battery pack was half full after 5 km (3.1 miles) and he was able to ride 11.75 km (7.3 miles) on a single charge. So, success! The battery pack did the job and if he needs to go further then he can build a bigger pack with some idea of how it would improve his travel distance.

Sadly though, he had to remove it all from his bike since he lives in Germany and European rules state that for it to be considered an electric bike, it must be pedal assisted and the speed must the be progressively reduced as it reaches a cut-off speed of 25 km/h (15 miles per hour). In other words, his E-bike was more like a moped or small motorcycle. But it did offer him some good opportunities for hacking, and that’s often enough. Check out his final assembly and testing in the video below.

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A Li-Ion Booster Pack, Done Right

We’re all used to battery booster packs containing a Li-ion or Li-poly cell and a little inverter circuit, they are a standard part of 21st century daily survival for those moments when smartphone battery lives don’t perform as advertised. But how many of us have considered what goes into them, and further how many of us have sought to produce the best one possible rather than a unit built at the lowest price?

It’s a course [Peter6960] has followed, producing a PCB that sits on the back of an 18650 cell holder. It follows the work of [GreatScott] in particular in its use of the TP4056 charger, MT3608 boost converter, and FS312F protection ICs. Many commercial modules omit any protection circuit, and the FS312F is of particular interest because it has a low 2.9V cut-off voltage that should lengthen the life of the cell. Files for the PCB can be found in a zip file hosted on Google Drive.

You might think that there was nothing new that could be learned about a Li-ion battery booster, but it’s always worth a look at a well-executed piece of work. We noticed he refers to Li-poly cells while using what appears to be a Li-ion 18650 cell. Most likely this is merely an oversight.

There is a lot to know about the characteristics and safety of the lithium-chemistry rechargeables, you may find [Sean Boyce]’s article on the subject to be an interesting read.

Comparing Making To Buying A Lithium Ion Battery Pack

At Hackaday we’re all about DIY. However, projects can have many components, and so there’s sometimes a choice between making something or buying it. In this case, [GreatScott!] wondered if it would be cheaper to make or buy a lithium-ion battery pack for his new eBike kit. To find out, he decided to make one.

After some calculations, he found he’d need thirteen 18650 cells in series but decided to double the capacity by connecting another thirteen in parallel. That gave him a 5 Ah capacity battery pack with a nominal voltage of 48.1 V and one capable of supplying a constant current of 40 A. Rather than connect them by soldering the nickel strips, he purchased a kWeld battery spot welder, adding to the cost of the build. He charged his new battery pack using his bench power supply but being concerned about uneven charging of the cells over the battery pack’s lifetime, he added a Battery Management System (BMS). The resulting battery pack powers his eBike motor just fine.

After adding up all the costs, he found it was only a tiny bit cheaper than prices for comparable battery packs on eBay, which were €24.4 per Ah (US$29.5 per Ah). The only way it would be cheaper is if he made multiple packs, spreading out the one-time cost of the battery spot welder. So that means it’s really up to your preference. See his video below to judge for yourself if you’d rather do it the DIY way. And then let us know what you’d do in the comments below.

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Assemble Your Own Modular Li-Ion Batteries

Low-voltage DC power electronics are an exciting field right now. Easy access to 18650 battery cells and an abundance of used Li-Ion cells from laptops, phones, etc. has opened the door for hackers building their own battery packs from these cheap cells. A big issue has been the actual construction of a pack that can handle your individual power needs. If you’re just assembling a pack to drive a small LED, you can probably get by with spring contacts. When you need to power an e-bike or other high power application, you need a different solution. A spot welder that costs $1000 is probably the best tool, but out of most hackers’ budget. A better solution is needed.

Vruzend v2 Battery Caps.

Enter [Micah Toll] and his Vruzend battery connectors, whose Kickstarter campaign has exceded its goal several times over. These connectors snap onto the ends of standard 18650 cells, and slot together to form a custom-sized battery pack. Threaded rods extend from each plastic cap to enable connection to a bus bar with just a single nut. The way that you connect each 18650 cell determines the battery pack’s voltage and current capability. There are a couple of versions of the connector available through the campaign, and the latest version 2.0 should allow some tremendously powerful battery pack designs. The key upgrade is that it now features corrosion-resistant, high-power nickel-plated copper busbars allowing current up to 20A continuous. A side benefit of these caps instead of welded tabs is that you can easily swap out battery cells if one fails or degrades over time. Continue reading “Assemble Your Own Modular Li-Ion Batteries”

Cross-Brand Adapter Makes for Blended Battery Family

Even though he’s a faithful DeWalt cordless tool guy, [Richard Day] admits to a wandering eye in the tool aisle, looking at the Ryobi offerings with impure thoughts. Could he stay true to his brand and stick with his huge stock of yellow tools and batteries, or would he succumb to temptation and add another set of batteries and chargers so he could have access to a few specialty lime green tools?

Luckily, we live in the future, so there’s a third way — building a cross-brand battery adapter that lets him power Ryobi tools with his DeWalt batteries. [Richard]’s solution is a pure hack, as in physically hacking battery packs and forcing them to work and play well together. Mechanically, this was pretty easy — a dead Ryobi pack from the recycling bin at Home Depot was stripped down for its case, which was glued to a Dewalt 20-v to 18-v battery adapter. The tricky part came from dealing with the battery control electronics. Luckily, the donor DeWalt line has that circuitry in the adapter, while Ryobi puts it in the battery. That meant simply transplanting the PCB from the adapter to the Ryobi battery shell would be enough. The video below shows the process and the results — Ryobi tools happily clicking away on DeWalt batteries.

While [Richard] took a somewhat brute-force approach here, we imagine 3D-printed parts might make for a more elegant solution and offer other brand permutations. After all, printing an adapter should be easier than whipping up a cordless battery pack de novo.

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