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Can we get battery-less electronic components on bikes?

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1/15/2022 4:52 PM

This article by member @wheelbased got me thinking, what's a logical endpoint for the trend of electrifying bike parts?

What's your best guess? Assume it's NOT an ebike (and if you can figure out how to power an ebike without batteries why are you reading my dumb, cold medicine-inspired post?)

A few of thoughts below but I'm more interested in how it COULD be workable instead of my uninformed guesses. This isn't my field at all so please educate me!

- Piezo (as outlined in the patent article above), not a lot of power (not enough to run a solenoid or stepper motor).
- Something similar to a self-winding watch for each component? No idea if this is feasible, increases cost and complexity of each component but makes it easy to add components,
- Dyno hub? They exist and are relatively cheap and reliable, but require special hubs and a way to distribute the power to other components
- Use the fork or shock (similar to a wave generator). Could be drop-in (like a Diaz Runt or the Flight Attendant stuff) but still requires distributing power to individual components.

I assume the big S's are working on this, what can we come up with?

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1/16/2022 8:31 AM

In the angling world, Shimano has what they call "DC" braking for baitcaster reels. It's basically a tiny magnetic power generator that also uses the magnets to to activate braking during a cast (to control line speed.) You can watch a short youtube video explaining it here.

My guess is something similar could be possible by using the rear hub to power a rear derailleur, after all, you only shift when you are moving. This is just a guess though, as I'm no engineer.

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1/16/2022 11:08 AM

taldfind wrote:

In the angling world, Shimano has what they call "DC" braking for baitcaster reels. It's basically a tiny magnetic power ...more

That's pretty cool tech, thanks! Seems to have the same problems as a dyno hub tho; requires a special hub and a way to distribute the power to the component that need it.

I wonder if it can be made small enough to fit in a jockey wheel/derailleur cage?

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1/16/2022 1:41 PM

I got an old mangled Di2 mech here, I might see what the minimum current would be to get it to move about, however it may need signal. I reckon a couple of CR2032 batteries in series would get it going, total weight.... 5grams?

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1/16/2022 1:44 PM
Edited Date/Time: 1/16/2022 1:51 PM

If a dyno in a hub could work surely something similar could be built into a gearbox transmission, like a pinion or something? Makes it more contained and more central for distribution to other parts of the bike via wires

Another interesting concept I have heard is that in fighter planes they use special carbon layups in the hull that allow them to use some of the fibers as electrical wires for connecting equipment

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1/16/2022 5:50 PM

Are we going to see solar panel/strips mounted to #plates?

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1/16/2022 6:17 PM

There are certainly electronic "self-winding" watches, but quartz watch movements use very little energy - running from a small silver oxide cell they will last several years running continuously, while some digital watches claim ten years.

Most self-charging watches these days use a solar cell because they're simpler and more robust, however even then the solar cell in Garmin's highest-end watches doesn't provide enough continuous power to keep its battery charged if the GPS radio is turned on.

I'm sure a solar cell could work well for something low powered and intermittent like a shifter, but AXS shifters for example get two years out of a CR2032 so battery replacement isn't particularly onerous.

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1/16/2022 8:22 PM

boozed wrote:

There are certainly electronic "self-winding" watches, but quartz watch movements use very little energy - running from a ...more

Damn you CR2032!

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1/16/2022 8:31 PM

How about a generator/dynamo built into the crank/bottom bracket? Less draw than a high idler bike. Would probably still need a small battery or capacitors to keep some reserve power but no plug in charging required.

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1/17/2022 12:32 AM

Braking is by far the largest and most consistent source of potential energy on a bike that won't take any additional energy from the rider. You'll definitely still need a small battery to store the energy from it though.

The only problems I see with this are that the magnets and coils needed to make this work are not light. The mechanism is also very very similar to an electric motor so I doubt this would ever be legal in a competitive setting.

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1/17/2022 6:43 AM

boozed wrote:

There are certainly electronic "self-winding" watches, but quartz watch movements use very little energy - running from a ...more

I didn't even get a year out of my CR2032 in my AXS shifter, where's my refund!?!?!?

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1/17/2022 1:26 PM
Edited Date/Time: 1/17/2022 1:27 PM

On a mountain bike it would be cool to capture the energy that is dissipated by the dampers in the suspension - charge a small battery rather than heat up some oil. Not sure how much energy you would get but with a little time and some damper curves would be easy to do.
Of the top of my head maybe you could drive the fluid through a positive displacement pump rather than a valve and hook that up to a generator.

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1/17/2022 3:31 PM

I think there are several patents out there for regenerative braking on bikes. If that were used on a non-ebike for shifting/seatpost etc. you would probably need a centralized battery to recharge then distribute the power to the various components. This would mean wires from the batter to the various components, which is less than ideal. One of the reasons I love AXS is the lack of wires.

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1/17/2022 4:36 PM

matmattmatthew wrote:

I think there are several patents out there for regenerative braking on bikes. If that were used on a non-ebike for ...more

This is great stuff, thank you all!

No wires and not having to recharge batteries feels like the goal, so given that:

- Fork, shock: damper-driven power generation
- Dropper: damper driven too, or maybe use the drop action?
- Rear mech: something driven off the jockey pulleys? (This one feels like the hardest to solve given how we treat derailleurs)
- Shifter: Piezo as outlined in the Shimano patent

My guess is all the components will need some kind of small onboard battery (w/ another way to charge it as backup) so at least the radio/Bluetooth will be available when the bike isn't being ridden.

I'm probably missing some really fundamental/critical pieces, what are they?

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1/17/2022 9:35 PM

matmattmatthew wrote:

I didn't even get a year out of my CR2032 in my AXS shifter, where's my refund!?!?!?

Hah, I'll cop that one, my mistake for quoting a manufacturer's claim

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1/18/2022 8:00 AM
Edited Date/Time: 1/18/2022 8:03 AM

Regenerative braking would be a PITA to implement, as you have additional braking components besides the hydraulic brake itself - are you just adding the regeneration to it? Are you modulating it to have a set total braking power independent of the regeneration amount?

F1 uses MOOG valves to modulate rear brakes in order to keep the same braking distribution front-to-rear regardless of how much regeneration is done. It's a bit different to bikes (one pedal vs. two levers and all), but bikes are also much simpler.

Same for suspension, plus road bikes don't have suspension (can't say that anymore when it comes to hydraulic brakes though). At the end of the day a single system should be (would be) used for both road and mountain bikes.

A friend of mine a while ago asked why hasn't Shimano, given the wiring and centralisation of their Di2, made a spindle based dynamo with a small (CR2032? tongue ) battery to start the system up and provide an initial charge to a capacitor that actually provides the power to do the shifts. Said capacitor would then be charged from the spindle dynamo during the ride, the battery is there only for the startup. You don't need a lot of generation in the dynamo to provide enough energy to do the shifting (as you do little shifting compared to the number of revolutions you do while riding) so the drag would be miniscule. The steel spindle Shimano still uses (which is a good thing) might require a special crank, but I think an aluminium spindle could be exploited to just insert some magnets into the inside of the spindle and have an appropriate BB shell with some coils and connected to the central control box. A correctly implemented BB and external wiring would make it retrofittable to any bike, but even internal wiring would very likely not be an issue given internal mounting of the Di2 battery is a thing on most road bikes.

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1/18/2022 3:50 PM

boozed wrote:

There are certainly electronic "self-winding" watches, but quartz watch movements use very little energy - running from a ...more

matmattmatthew wrote:

I didn't even get a year out of my CR2032 in my AXS shifter, where's my refund!?!?!?

gotta ride less!

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