Fail Of The Week: Alternator Powered Electric Go-Kart Doesn’t Go

October 25, 2021 by Adam Fabio 21 Comments

What do you give a six-year-old who loves going fast but doesn’t like loud noises? Convert a gas go-kart to electric of course! (Video, embedded below.) That goal started [Robert Dunn] of Aging Wheels down a long path toward a go-kart that almost, but doesn’t quite… work.

If you’ve watched any of [Robert’s] videos, you know he doesn’t take the easy path. The man owns a Trabant and Reliant Robin after all. Rather than buy a battery pack, he built his own 5S24P pack from individual LiFePO4 cells. Those cells generally are spot welded, so [Robert] built an Arduino-controlled heirloom-quality spot welder. Now while the welder could handle thin nickel strips, it wasn’t up the task of welding high current nickel-plated copper. When attempts at a solution failed, [Robert] built a system of clamped copper bus bars to handle the high current connections for the batteries.

If batteries weren’t hard enough, [Robert] also decided he wasn’t going to use an off-the-shelf motor for this project. He converted a car alternator to operate as a brushless motor. We’ve covered projects using this sort of conversion before. Our own [Jenny List] even wrote a tutorial on it. [Robert] unfortunately has had no end of trouble with his build.

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Magnetic Bearings Put The Spin On This Flywheel Battery

July 22, 2021 by Dan Maloney 35 Comments

[Tom Stanton] is right about one thing: flywheels make excellent playthings. Whether watching a spinning top that never seems to slow down, or feeling the weird forces a gyroscope exerts, spinning things are oddly satisfying. And putting a flywheel to work as a battery makes it even cooler.

Of course, using a flywheel to store energy isn’t even close to being a new concept. But the principles [Tom] demonstrates in the video below, including the advantages of magnetically levitated bearings, are pretty cool to see all in one place. The flywheel itself is just a heavy aluminum disc on a shaft, with a pair of bearings on each side made of stacks of neodymium magnets. An additional low-friction thrust bearing at the end of the shaft keeps the systems suitably constrained, and allows the flywheel to spin for twelve minutes or more.

[Tom]’s next step was to harness some of the flywheel’s angular momentum to make electricity. He built a pair of rotors carrying more magnets, with a stator of custom-wound coils sandwiched between. A full-wave bridge rectifier and a capacitor complete the circuit and allow the flywheel to power a bunch of LEDs or even a small motor. The whole thing is nicely built and looks like a fun desk toy.

This is far from [Tom]’s first flywheel rodeo; his last foray into storing mechanical energy wasn’t terribly successful, but he has succeeded in making flywheels fly, one way or another.

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An Alternator Powered Electric Bicycle Gives Rotor Magnetic Field Insight

January 24, 2021 by Jenny List 63 Comments

For anyone involved in the construction of small electric vehicles it has become a matter of great interest that a cheap high-power electric motor can be made from a humble car alternator. It’s a conversion made possible by the advent of affordable three-phase motor controllers, and it’s well showcased by [austiwawa]’s electric bicycle build video (embedded below).

The bike itself is a straightforward conversion in which the motor powers the rear wheel via an extra sprocket. He tried a centrifugal clutch with limited success, but removed it for the final version. Where the interest lies in this build is in his examination of Hall effect sensor placement.

Most alternator conversions work without sensors, though for better control it’s worth adding these magnetic sensors to allow the controller to more directly sense the rotation. He initially placed them at the top of the stator coils and found them to be ineffectual, with the big discovery coming when he looked at the rotor. The electromagnet in the rotor on a car alternator has triangular poles with the field concentrated in the centre of the stator, thus a move of the sensors to half way down the stator solved the problem. Something to note, for anyone converting an alternator.

Should you wish to give it a try, a year ago we published a primer on turning car parts into motors.

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RC Lawn Mower Keeps The Grass Greener On Your Side Of The Fence

June 1, 2020 by Sven Gregori 23 Comments

For some people, mowing the lawn is a dreaded chore that leads to thoughts of pouring a concrete slab over the yard and painting it green. Others see it as the perfect occasion to spend a sunny afternoon outside. And then there are those without the luxury of having a preference on the subject in the first place. [elliotmade] for example has a friend who’s sitting in a wheelchair, and would normally have to rely on others to maintain his lawn and form an opinion on the enjoyability of the task. So to retain his friend’s independence, he decided to build him a remote-controlled lawn mower.

After putting together an initial proof of concept that’s been successfully in use for a few years now, [elliotmade] saw some room for improvement and thought it was time for an upgrade. Liberating the drive section of an electric wheelchair, he welded a frame around it to house the battery and the mower itself, and added an alternator to charge the battery directly from the mower’s engine. An RC receiver that connects to the motor driver is controlled by an Arduino, as well as a pair of relays to switch both the ignition and an electric starter that eliminates the need for cord pulling. Topping it off with a camera, the garden chores are now comfortably tackled from a distance, without any issues of depth perception.

Remote-controlling a sharp-bladed machine most certainly requires a few additional safety considerations, and it seems that [elliotmade] thought this out pretty well, so failure on any of the involved parts won’t have fatal consequences. However, judging from the demo video embedded after break, the garden in question might not be the best environment to turn this into a GPS-assisted, autonomous mower in the future. But then again, RC vehicles are fun as they are, regardless of their shape or size.

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Car Alternators Make Great Electric Motors; Here’s How

January 16, 2020 by Jenny List 197 Comments

The humble automotive alternator hides an interesting secret. Known as the part that converts power from internal combustion into the electricity needed to run everything else, they can also themselves be used as an electric motor.

The schematic of a simple automotive alternator, from US patent 3329841A filed in 1963 for Robert Bosch GmbH . — The schematic of a simple automotive alternator, from US patent 3329841A filed in 1963 for Robert Bosch GmbH.

These devices almost always take the form of a 3-phase alternator with the magnetic component supplied by an electromagnet on the rotor, and come with a rectifier and regulator pack to convert the higher AC voltage to 12V for the car electrical systems. Internally they have three connections to the stator coils which appear to be universally wired in a delta configuration, and a pair of connections to a set of brushes supplying the rotor coils through a set of slip rings. They have a surprisingly high capacity, and estimates put their capabilities as motors in the several horsepower. Best of all they are readily available second-hand and also surprisingly cheap, the Ford Focus unit shown here came from an eBay car breaker and cost only £15 (about $20).

We already hear you shouting “Why?!” at your magical internet device as you read this. Let’s jump into that.

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How Do They Synchronize Power Stations With The Grid?

July 5, 2017 by Jenny List 58 Comments

There are probably times in every Hackaday reader’s life at which you see something and realise that the technology behind it is something you have always taken for granted but have never considered quite how it works. Where this is being written there was such a moment at the weekend, an acquaintance on an amateur radio field day posted a picture of three portable gas-powered alternators connected together and running in synchronization. In this case the alternators in question were fancy new ones with automatic electronic synchronization built-in, but it left the question: how do they do that? How do they connect a new power station to the grid, and bring it into synchronization with the line? There followed a casual web search, which in turn led to the video below the break of a bench-top demonstration.

If two AC sources are to be connected together to form a grid, they must match each other exactly in frequency, phase, and voltage. To not do so would be to risk excessive currents between the sources, which could damage them and the grid infrastructure. The video below from [BTCInstrumentation] demonstrates in the simplest form how the frequencies of two alternators can be matched, by measuring the frequency difference between them and adjusting their speed and thus frequency until they can be connected. In the video he uses neon bulbs which flash at the difference frequency between the two alternators, and demonstrates adjusting the speed of one until the bulbs are extinguished. The two alternators can then be connected, and will then act together to keep themselves in synchronization. There are further videos in which he shows us the same process using a strobe light, then demonstrates the alternators keeping themselves synchronized, and phase deviation between them.

Of course, utility employees probably do not spend their time gazing at flashing neon bulbs to sync their power stations. The same measurements are not performed by eye but by electromechanical or electronic systems with automatic control of the contactors, just as they are in the fancy electronic alternator mentioned earlier. But most of us have probably never had to think about synchronizing a set of alternators, so to see it demonstrated in such a simple manner should fill a knowledge gap even if it’s one only of idle curiosity.

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Alternator Becomes Motor For This Electric Go-kart

August 14, 2016 by Dan Maloney 49 Comments

Growing up in the 70s and 80s, a go-kart was a quick ticket to coolness, second maybe to a mini-bike. In both cases, a welded steel tube frame and a cast-off lawnmower engine were all that stood between you and neighborhood glory. Looks like a couple of engineering students caught the retro juvenile delinquent bug and built this electric go-kart for their final project.

While the frame for [Adrian Georgescu] and [Masoud Johnson]’s build was a second-hand find, the powertrain is all custom. They targeted a power output of 3 kW but found no affordable motors in that range. So, in true hacker fashion, they rolled their own motor from a used Subaru alternator. The three-phase motor controller came from an electric scooter, three LiPo packs provide the juice, and a pair of Arduinos takes care of throttle control, speed sensing, and sending data to the virtual dashboard on an Android phone. Some lights and a snappy red and black paint job finished off the build. While the video below shows that the acceleration isn’t exactly neck-snapping in the Tesla style, the e-kart can build up to a good speed – 53 km/h. Not too shabby, and no deafening engine right behind your head.

If you’ve got the e-kart bug, best check out some of our previous posts, like this kart built from off-the-shelf components, or this four-wheel-drive mini-kart. Any way you build it, you’ll rule the cul-de-sac.

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