Super Capacitor Bike

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[robotslug]

Capacitors for taking off quickly from the start, li-ion batteries for cruising, with regenerative braking recharging your capacitors specifically. Now that'd be neat!

[jamesmcpherson]

As a single speed, with regenerative braking this would be absolutely brilliant for urban use. You really only need assist to get to speed. Energy could be dependent on mass, so this would be awesome for cargo bikes starting up.

[MakersMuse]

I reckon you're definitely onto something with the regen potential, almost like a boost to an additional lithium pack. Love how well the ultra basic BLDC controller works! Would love to see a speed limit test on it with some big voltage behind it ;)

[avgvstvs]

That regenerative braking idea is actually really cool! If you can gain roughly 40% of the energy used to cycle this system with an optimized battery-capacitor storage solution can be genuinely useful, an ebike you never have to charge, pedal when you can and use the electric power to when going up inclines or when you get tired.

[dancollins]

The fact the bike chain tried to stick to the motor indicates there is magnetic flux that escapes the motor assembly. Optimise the magnetic flux path, and you'll get a significant increase in motor performance

[OlaftheGreat]

Explains in detail why capacitors are bad for electric vehicles

"And that's why I'm going to make a supercapacitor electric bike"

[andresilvasophisma]

It's actually great to see it almost fully recharging the capacitors when you go downhill.
This would be great for electric scooters if the energy storage amount was bigger.
Massive props for creating the electric motor from scratch.

[saitamatechno]

He didnt only test the capacitors, he also build a BLDC motor from scratch. This is insanely amazing!

[PlasmaChannel]

Cool project Tom. "Supercap" in the title pretty much grabs me any time. Have you considered iron cores for the coil cores? This should magnetically saturate more efficiently. The rest of the rotor could stay aluminum, and just have coil cores be iron. You'd see a large increase in torque, though likely a moderate decrease in range.

[noncalamari]

Differences in capacity and self-discharge rate means that your series capacitor bank is going to drift out of balance very quickly. This means that individual caps can be driven to reverse polarity during discharging and/or some caps will be overvolted during charging. You can get little balancer boards for these supercaps - definitely indicated in this application.

[sbkenn]

A steel plade on the opposite side of the rotor will increase the flux-density on the coil side, AND eliminate the magnetic attraction on the chain. Alternatively, place another set of coils on that side, also with a back-plate. Also, a boost controller will keep the motor voltage up even when the capacitor voltage drops.

[christmassnow]

In theory, you should set the motor in the first bike to serve as generator while regenerative braking. You can use this feature to charge the capacitors using your leg power, and store this power for uphill biking part of the way.

[johngreen]

The motor torque is created by magnetic flux trying to find a path of minimum reluctance. This is what really happens when you align magnets NS NS (relatively straight wide magnetic path - min reluctance) vs NS SN (magnetic path pinched between magnets - max reluctance). The problem with your design is that most of the magnetic path is in the air around the motor, so reluctance changes are small - low torque. You can greatly reduce that fixed reluctance by "closing" the circuit by e.g. placing mild steel plates on each side of the motor in such way they touch the magnets and electromagnets. This will also reduce the magnetic flux leakage attracting (trying to find its way through) the chain. As someone mentioned eddy currents may cause power losses, especially at high rpms - avoid conductive materials in the magnetic path.

[ssjgohan]

Ah, I love these projects because they're... pretty good at explaining why supercapacitors don't really have an application in vehicles. The charge rate of a capacity may be high, but because they have such low capacity the actual volumetric and gravimetric power density is usually on par with or sometimes even worse than batteries. Also, batteries tend to charge fastest at relatively low charge, while supercaps charge at very low power from empty and only really reach their full potential around 2/3rds charge.

[socaliguy]

Given the weight of the super capacitors, I'm surprised you didn't just quadrupole the battery count. Maybe, for round 2, you could integrate the supercapacitors to the regen braking system and use Lithiums for drive.

[halfblood_dragn]

hmmm, charge the capacitors with the bike

[andi_]

Tip for the next time you wind coils: Do 5 or 10 revolutions before adding on the calculator. Speeds up the process by a lot because you don't have to switch after every revolution and pick up the wire again, and 5 is still easy to count (10 also with some practice) :)

[ProjectPhysX]

Very cool project!
Just some thoughts on the DIY motor: Maybe align the magnets in a Halbach array and use iron cores in the coils. Should vastly improve efficiency and torque.

[david]

Usually if i ride down a small hill, I can get around 40% of the way up the next hill just with the momentum gathered. If you trialed the bike on a series of small up and down hills whilst continuing with momentum i bet it would keep up a good pace, add in some strategic pedalling and it will be flying. Would be good to see a pump track version that automatically detects when to apply power/regenerate

[ap]

Man, you need back iron in both rotor and stator. Just adding this would make the motor 2-3 times more powerful.