Hoverboard Teardown | Hacker News Reader

Hoverboard Teardown

blog.fictiv.com

38 pointsfictivmade19 comments

No mention of the battery pack or charger, the most troublesome components.

The in-wheel motors are kind of neat. Those could be useful for motion control projects, especially since they're three-phase synchronous and can be run all the way down to zero speed with high torque. More info about the power drive system for the motors would be useful. What are they using to switch all that current? No heat sinks are visible, so either the switching is really efficient or the drive electronics will overheat.

It's good to see precision motor control at this price point. These devices are rather impressive technically. Once somebody starts shipping them with safe batteries and full battery protection circuitry, they could be popular again. Boosted brand electric skateboards got it right; they used a safer battery chemistry, figuring the boards would be abused. Good call.

Most recent major hoverboard fire: Orlando, FL, 3 days ago. 3 apartments destroyed.

If you're interested in a hoverboard battery pack and motor drive, take a look at the hoverboard teardown that I did with iFixit: https://ifixit.org/blog/7821/swagway-teardown-hoverboards/

That's a more useful article. Thanks.

The three motor lead colors not matching is amusing. Those are three-phase motors; any connection will work, but half of them will make the motor go backwards. Swapping any two leads will reverse the motor. I wonder if, with the colors correct, one motor is in reverse.

> What are they using to switch all that current? No heat sinks are visible, so either the switching is really efficient or the drive electronics will overheat.

My guess, pretty well verified by some similar pics in teh teardown by kens in a sibling comment, is that the "the main PCBA was located. There were fourteen screws and washers holding down the board, which was probably done to reduce vibration on the critical components."

is probably the mosfets attached to the backing panel for heat-sinking, rather than specifically for rigidity.

If you look at one of hte middle images[1] you can see what looks like imprints of thermal paste around each of the mounting holes.

[1] https://daks2k3a4ib2z.cloudfront.net/5654e7207deb65b23ea76b7...

That is indeed thermal paste and there was an aluminum backing acting as a heat sink under the PCBA.

Might be a brushless DC, not an AC motor, although it's still basically a 3 phase setup.

Yes, it's pretty clearly brushless DC, since it's driven by an H-bridge and has the Hall-effect position sensor. But as you say, it's still 3-phase, just square rather than AC sinusoids. A description of brushless DC control is here: http://www.nxp.com/files/microcontrollers/doc/app_note/AN405...

My only complaint is that these feel really unstable at above walking speeds.

Is there a way to make the steering less sensitive at hi speeds or even lock the two sides together?

When I see teardowns for most computers/gadgets, I'm always puzzled by the size of the battery. Somewhere someone decided that battery life barely long enough to sell the product, is good enough.

What I expect to see (and I do in Apple products for instance) is the battery dominating the volume of the product.

The average Apple product cost $890. The Average hoverboard cost $80.

Now figure this one out: https://www.youtube.com/watch?v=KEDrMriKsFM#t=30 (volume warning)

Best theory so far it is it just a quadcopter with some greenscreen video photoshopping

But if it is somehow real, wow. Imagine THOSE all over your city.

That is the same guy who make the water based one that attached to jetskis

I just cannot fathom any portable powersource that would produce that much energy for that much weight over 10 minutes. Even large scale RC engines have weight limits below a fully grown man.

He has a propellant tank on his back and it's clearly some kind of combustion taking place. Still, seems a bit implausible.

As someone who came of age in the 1980s, the fact that these devices are called "hoverboards" is extremely grating every time I hear it.

What's the energy density on these batteries. I can't believe that tiny thing can move 250 lbs around for over an hour.

It's a 36 volt, 4.4AH Li-ion battery at approximately 172 grams. That puts the energy density at about 915 wH/KG in ideal conditions.