Shimano DI2 battery Rechargeable by Bottom Bracket..why not?

[andreszucs]

I saw this concept online the other day....so why not add the same idea for shimano DI2 system????? so obvious....Bottom braket would do the job with our power.

http://www.yankodesign.com/2010/01/04/c ... ger-power/" onclick="window.open(this.href);return false;

[djconnel]

.. because people want their bottom bracket to have a minimum amount of friction. It hardly makes sense to spend $kkk for electronic shifting, the advantage of which is small fractions of a second in shifts, only to squander power charging a generator.

[andreszucs]

But that would be better then get up in the morning ready for a bike ride and find out that the DI2 battery is out

this could solve this problem....just a few revolution and the shifting would be back to the game....

[andreszucs]

and NEVER need to plug in the wall anymore.....

[djconnel]

There's another solution to not having to plug in your bike...

[CerveloBert]

Great points...

But again, it defeats the purpose of having this super-light, high-tech, non-friction forming, smooth-bearing drivetrain. The added weight of a generator needs to be taken into consideration as well.

When RC Cars were moving to LIPO from NiMH batteries, they also went through an extensive marketing overhaul. This was due to the fact that LIPO or LI ion batteries were that much more lightweight, and denser in energy than NiMH. This ultimately meant faster cars. I mean, I'm sure some geek could've built an RC car with redundant power from generator + battery. Is that something that you'd want though? Great idea for power conservation, but not viable for racing. Same goes for the bike, you can be happy that you never have to plug in your Di2 or recharge a battery, but I'm not sure that's the concern once you get on the road and start bumping shoulders or when you want to bridge a gap.

[DYG]

Obviously a generator powered Di2 would not make sense for a bike that you actually raced, because of the increased drag, but I think it is a really cool idea for a high performance road bike designed for long rides.

Check out this bike: http://oregonmanifest.com/constructor/chapman-cycles/

Schmidt SON generator hub makes power, which can charge a battery/eWERK, power LED lights, and give juice for the Di2 system. With the eWERK device you can power your iPhone, Garmin GPS, prostate massager, or whatever.

[CerveloBert]

prostate massager, or whatever.

That's what I need built into my saddle.

[andreszucs]

Focusing on the design Itself, as the picture shows, If it's really possible to turn the circle with one finger using just the weight of the battery...I really don't believe that the friction involved is bad...look at the cell phone battery weight. Now imagine two legs with large muscle groups spinning ... not bad at all.

Of course that would be amazing if the concept illustrated above would be possible .... very low friction. Applied to the bike, I envision something very similar to this, something integrated like this battery with a hole in it and the BB connected.

[maxxevv]

Wouldn't it be easier to have an emergency plug in using "AA" cells like they have for handphones ???

At least you can charge anywhere that sells AA cells ...

[prendrefeu]

There's another solution to not having to plug in your bike...

[thisisatest]

although Mavic's Mektronic system was a complete flop, it did use some pretty cool ideas. like the rear derailleur (wireless) just used a cr2032 battery. when you shifted, the system would just drop a magnetic pin down, where two rods were moving left/right, driven by the upper derailleur pulley. the pin would catch the rod, and one shift would take place. so although the signals were electronic, the rider still actually completed the shift. (this also satisfied the letter of UCI's rules requiring everything to be human powered. im sometimes surprised di2 is even legal for racing!) this also used very little battery power, and there was only an imperceptively small increase in drag to complete the shift. unlike a generator, that is creating drag all the time, even when the system doesnt need the juice.

[allezkmiec]

Seems to me that if a person is simply able to remember to plug their bike in once every several hundred hours, the issue of the dead battery is moot. And really, if you can't remember to do that, you should take up something like Wii bowling.

[andreszucs]

You need to consider the hassle of having to replace the battery when it does not take any more load. Besides, if a concept like this could ever be applied, the battery may not even be necessary, since the power would be generated by pedaling and not by the battery.

You must agree with me...that would be cool.

[madmole]

For the really small power required to top up the Di2 battery, why not just have a wire coil on the side of the BB and a magnet on the crank, no added friction and a small current generated every stroke to pulse into the battery. No friction, very liitle extra weight (bet you already have computer/cadence magnets installed anyway). Built into the frame this would be very aero and unoticable

My Seiko Kinetic watch has been running for 15 years using this method, and my yamaha Enduro Motorcycle generates 6V to run 40Watts of lights by spinning a magnet on the crankshaft past a large coil build into the engine case. Its also how those shake to charge torches work. Yes technically there is a very small resistance generated into the magnet against rotation but its miniscule and could be kept low by design. The sheer number of rotations would more than compensate, that battery needs a few hundred, we are doing 6000 an hour