Electric Chainsaw Teardown

An electric chainsaw with its case removed

For his Beyond Unboxing series, [Charles] tore apart a Ryobi cordless chainsaw to get a better look at how this battery powered tool works.

Inside he found a three-phase motor and controller. This motor looks like it could be useful in other projects since it has a standard shaft. The battery pack was popped open to reveal a set of LG Chem 21865 cells, and some management hardware.

With all the parts liberated from the original enclosure, [Charles] set up the motor, controller, and battery on the bench. With a scope connected, some characterization of the motor could be done. A load was applied by grabbing the spinning shaft with welding gloves. [Charles] admits that this isn’t the safest way to test a motor.

While it is a very fast motor, the cut-in speed was found to be rather low. That means it can’t start a vehicle from a stop, but could be useful on e-bikes or scooters which are push started.

This chainsaw a $200 motor, controller, and battery set that could be the basis of a DIY scooter. It sounds great too, as the video after the break demonstrates.

[Thanks to Dane for the tip!]

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3kW Electric Scooter

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[Exco] had been playing around with the idea of building an electric scooter for a while now, and over the holidays he decided to just do it.

Similar to the motorized long board we shared last month, this scooter makes use of an RC hobby motor — in this case, a 63mm 3kW brushless outrunner (for a RC plane), coupled with a 100A ESC. He bought the scooter (“kick board”) off eBay for cheap, and spent a few days in the machine shop modifying it. It has better wheels now, and custom milled aluminum brackets for mounting the motor. The drive system uses a belt and pulley with a sliding rail to provide tensioning.

To power it, he bought a bunch of 2.5Ah, 18V LiPo packs on eBay originally from a Makita drill set. He then sorted out the cells, removed the dead ones, and soldered everything together for his own Frankenstein pack to balance them. The final configuration features twenty-one 18650 lithium cells. He even shrink wrapped it, which makes it look relatively professional!

It’s controlled by a push-button potentiometer hooked up to the ESC. Theoretical top speed is about 27km/h @ 1285RPM, and they managed to get it up to 25km/h in a real test. There’s more info over at the Endless Sphere forum, and we’ve got two test videos for you after the break.

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Electric Snow Scooter

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[Dane] decided he wanted to make a rather large electric scooter, capable of taking him through even the most inclement weather — that’s right, even snow.

Well, after about 18 months of stop and go work it is finally complete — for now. It features an impressive 7kW brushless 3-phase motor, a massive lithium ion battery pack and more custom parts then you could shake a stick at!

The frame started out as one of those big push scooters from the 80’s, in fact, it is the same as the one shown in Macklemore’s Thrift Shop video (pic)! But since then it has had many a modification done to it — it looks as though the front end is the only part that wasn’t touched!

He’s got an incredible build log  his website, so if you want to build your own (you will once you’ve seen the video after the break), it’s a great starting point.

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Self balancing unicycle built from old scooter

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[Glenn] had an old electric scooter/motorcycle in his garage that had long ago given up the ghost. Without a working battery and motor controller this scooter wasn’t beyond repair, but [Glenn] thought he could use it to build something much, much cooler. What he came up with is a self-balancing unicycle that borrows inspiration from a Segway and other self-balancing robots.

After cutting the drive chain off his scooter, [Glenn] began work on installing a new motor controller and battery. To make this unicycle balance itself, he would need a few gyroscopes and accelerometers provided via an Arduino and Sparkfun IMU shield.

After tuning his PID loop, [Glenn] hopped on his new ride and took it for a spin with the help of a pair of ski poles. It’s much easier to ride than a traditional unicycle and [Glenn] says he’s getting better at riding it.

A123 LiIon battery pseudo extra


Every so often I have to slap myself in the head. I’m surprised that we haven’t covered these things by now. DeWalt’s been selling a LiIon 36 volt battery pack that’s full of the latest A123 cells. These are the same ones that were used in the Killacycle. (I think they’ve got a new batch of cells now).

A while back, [Jeff] sent in a circuit for using multiple packs, leaving the internal BMS in place. [The link is fixed now]

[Robert] sent in a scooter that’s been designed to run these same cells. The custom fabrication and machine work looks fantastic.