lithium ion

47 Articles

An E-Bike Battery Pack Without Spot Welding

July 3, 2018 by 44 Comments

In somewhat of a departure from their normal fare of heavy metal mods, [Make It Extreme] is working on a battery pack for an e-bike that has some interesting design features.

The guts of the pack are pretty much what you’d expect – recovered 18650 lithium-ion cells. They don’t go into details, but we assume the 52 cells were tested and any duds rejected. The arrangement is 13S4P, and the cells are held in place with laser-cut acrylic frames. Rather than spot weld the terminals, [Make It Extreme] used a series of strategically positioned slots to make contacts from folded bits of nickel strip. Solid contact is maintained by cap screws passing between the upper and lower contact frames. A forest of wires connects each cell to one of four BMS boards, and the whole thing is wrapped in a snappy acrylic frame. The build and a simple test are in the video below.

While we like the simplicity of a weld-less design, we wonder how the pack will stand up to vibration with just friction holding the cells in contact. Given their previous electric transportation builds, like this off-road hoverbike, we expect the pack will be put to the test soon, and in extreme fashion.

Continue reading “An E-Bike Battery Pack Without Spot Welding” →

Testing DIY battery pack on E-bike

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

May 28, 2018 by 19 Comments

[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.

Continue reading “[GreatScott] Tests His DIY Battery Pack On His E-Bike” →

Make or buy lithium ion battery pack

Comparing Making To Buying A Lithium Ion Battery Pack

May 1, 2018 by 31 Comments

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.

Continue reading “Comparing Making To Buying A Lithium Ion Battery Pack” →

Cordless Tool Battery Pack Turned Into Portable Bench Supply

March 24, 2018 by 18 Comments

Say what you want about the current crop of mass-marketed consumer-grade cordless tools, but they’ve got one thing going for them — they’re cheap. Cheap enough, in fact, that they offer a lot of hacking opportunities, like this portable bench power supply that rides atop a Ryobi battery.

Like many of the more common bench supply builds we’ve seen,  [Pat K]’s more portable project relies on the ubiquitous DPS5005 power supply module, obtained from the usual sources. [Pat K] doesn’t get into specifics on performance, but supplied with 18 volts from a Ryobi One+ battery, the DC-DC programmable module should be able to do up to about 16 volts. Mating the battery to the supply is easy with the 3D-printed case, which has a socket for the battery that mimics the sockets on tools from the Ryobi line. It’s simple and effective, as well as neatly executed. The files for the case are on Thingiverse; sadly, only an STL file is included, so if you want to support another brand’s batteries, you’ll have to roll your own.

Check out some of the other power supplies we’ve featured that use the DPS5005 and its cousins, like this nice bench unit. We’ve also covered some of the more hackable aspects of this module, such as an open-source firmware replacement.

Lithium Ion Versus LiPoly In An Aeronautical Context

October 23, 2017 by 32 Comments

When it comes to lithium batteries, you basically have two types. LiPoly batteries usually come in pouches wrapped in heat shrink, whereas lithium ion cells are best represented by the ubiquitous cylindrical 18650 cells. Are there exceptions? Yes. Is that nomenclature technically correct? No, LiPoly cells are technically, ‘lithium ion polymer cells’, but we’ll just ignore the ‘ion’ in that name for now.

Lithium ion cells are found in millions of ground-based modes of transportation, and LiPoly cells are the standard for drones and RC aircraft. [Tom Stanton] wondered why that was, so he decided to test the energy density per mass of these battery chemistries, and what he found was very interesting.

The goal of [Tom]’s experiment was to test LiPoly against lithium ion batteries in the context of a remote-controlled aircraft. Since weight is what determines flight time, cutting even a few grams from an airframe can vastly extend the capabilities of an aircraft. The test articles for this experiment come in the form of a standard 1800 mAh LiPoly battery and four 18650 cells wired together as a 3000 mAh battery. Here’s where things get interesting: the LiPoly battery weighs 216 grams for an energy density of 0.14 Watt-hours per gram. The lithium ion battery weighs 202 grams for an energy density of 0.25 Watt-hours per gram. If you just look at the math, all drones are doing it wrong. 18650 cells appear to have a much higher energy density per mass than the usual LiPoly cells. How does that hold up in a real-world test, though?

Using his neat plane with 3D printed wing ribs as the testbed, [Tom] plugged in the batteries and flew around a field for the better part of an afternoon. The LiPo flew for 41.5 minutes, whereas the much more energy dense lithium ion battery flew for 36.5 minutes. What’s going on here?

While the lithium ion battery has a much higher capacity, the problem here is the internal resistance of each battery chemistry. The end voltage for the LiPo was a bit lower than the lithium ion battery, suggesting the 18650 cells can be run down a bit further than [Tom]’s test protocol allowed. After recharging each of these batteries and doing a bit of math, [Tom] found the lithium ion batteries can fly for about twice as long as their LiPo counterparts. That means an incredibly long test of flying a plane in a circle over a field; not fun, but we are looking forward to other people replicating this experiment.

Continue reading “Lithium Ion Versus LiPoly In An Aeronautical Context” →

Battery Management Module Hacked For Lithium-Iron Battery Bank

September 14, 2017 by 37 Comments

In a departure from his usual repair and tear down fare, [Kerry Wong] has set out on a long-term project — building a whole-house battery bank. From the first look at the project, this will be one to watch.

To be fair, [Kerry] gave us a tease at this project a few months back with his DIY spot welder for battery tabs. Since then, he appears to have made a few crucial design decisions, not least of which is battery chemistry. Most battery banks designed for an inverter with enough power to run household appliances rely on lead-acid batteries, although lithium-ion has certainly made some inroads. [Kerry] is looking to run a fairly small 1000-watt inverter, and his analysis led him to lithium-iron cells. The video below shows what happens when an eBay pack of 80 32650 LiFePo4 cells meets his spot welder. But then the problem becomes one of sourcing a battery management system that’s up to the charge and discharge specs of his 4s battery pack. We won’t spoil the surprise for you, but suffice it to say that [Kerry] really lucked out that only minimal modifications were needed for his $9 off-the-shelf BMS module.

We’re looking forward to seeing where this build goes, not least because we’d like to build something similar too. For a more traditional AGM-based battery bank, check out this nicely-engineered solar-charged system.

Continue reading “Battery Management Module Hacked For Lithium-Iron Battery Bank” →

This Electric Longboard Collapses For Air Travel

September 8, 2017 by 26 Comments

How do you manage to get an electric off-road longboard past TSA and onto an international flight? Simple — make it a collapsible longboard that fits into a carry-on bag.

The mechanical and electrical feats accomplished by [transistor-man] may not be the most impressive parts of this hack. We’re pretty impressed by the build, starting as it did with the big knobby tires and front truck from an unused mountain board and the hub motor from a hoverboard, turning this into a trike. The incredible shrinking chassis comes courtesy of a couple of stout drawer slides and cam locks to keep it locked in place; collapsed, the board fits in a carry on bag. Expanded, it runs like a dream, as the video below shows.

But we think the really interesting part of this hack is the social engineering [transistor-man] did to ensure that the authorities wouldn’t ground his creation for electrical reasons. It seems current rules limit how big a battery can be and how many of them can be brought on a flight, so there was a lot of battery finagling before his creation could fly.

Electric longboards look like a real kick, whether they be all-aluminum or all-plastic, or even all-LEGO. This one, which went from concept to complete a week and a half before the flight, really raises the bar.

Continue reading “This Electric Longboard Collapses For Air Travel” →