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PostPosted: Thu Dec 31, 2009 12:29 am 
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Super_fast wrote:
For the battery I would suggest to simply replace the 2 cells, with 2 other, but lighter, cells. Going back to 1 single cell will require a voltage booster, too much of hassle, especially when you aren't an EE.

Take a look here for example: http://www.all-battery.com/li-polyersinglecells.aspx
The lightest option weights only 0.95 grams. But don't shift to often, because the capacity is only 25 mAh :roll: Something a little heavier would be a better choice, for example one with a capacity of 160 mAh weights only 4 grams. For comparision when the orinal cells are of the AA format (14500), the capacity is 900 mAh and the weight is 21 grams a cell. So weight savings with the 160 mAh cells would be: 2*21-2*4=34 grams :thumbup:

And get rid of plastic housing, heat shrink tape is a lot lighter :beerchug:


The 300mAh LiOn batteries weigh the same than the 160mAh ones...so you can reduce the weight 34gr with a 1/3 capacity battery. If the standard battery can survive 1000km, the 300mAh can be a very good option as a race-only battery (much better for cyclocross or TT)

Coloclimber, I'm expecting what you will be able to do...

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PostPosted: Thu Dec 31, 2009 2:46 am 
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A friend of mine works for Shimano, he is part of their technical support group.
Last night, we were talking about modifying the Di2 group - and well, apparently people have been getting about 3,000 miles on them between charges.

So, really, that's around 1,800 or so miles.

I wouldn't mind charging every 500 miles, even!

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Posted: Thu Dec 31, 2009 2:46 am 


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PostPosted: Thu Dec 31, 2009 2:59 am 
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I am on the original charge still from October 25th. Still going strong. Not even at 50% yet. The battery is definitely the place to save the grams.

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PostPosted: Thu Dec 31, 2009 3:07 am 
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Shimano's battery estimate is very conservative. I would be ok with a 1-2 week battery life.


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PostPosted: Thu Dec 31, 2009 3:11 am 
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read this article. battery tech coming out in the next 4 years. electric cars should be a reality by 2015. interesting times we are living in.

http://www.greencarcongress.com/2009/12 ... .html#more


di2 looks overbuilt. next iteration of di2, shimano can easily shave 100gm from the derailleurs/battery/holder.

one question for di2 owners. should i remove the battery for winter storage?

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PostPosted: Thu Dec 31, 2009 3:23 am 
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nitropowered wrote:
Shimano's battery estimate is very conservative. I would be ok with a 1-2 week battery life.


I would think about 500miles or 800km taking into account battery deterioration over time would be more than suffice for 99.9% of the people out there. So, probably 35-40% of the current amperage capacity would be suffice.

Would be most interesting to trim a battery to that weight though.

So... who's willing to sacrifice a battery and a harness here ... that's over EURO$200 to be thrown out the window for an 'experiment' ... :P


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PostPosted: Thu Dec 31, 2009 4:08 am 
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it would more be just a harness getting cut up. Cut off the cable going to the battery connector, solder on some new connectors and plug in your new battery.

Probably can save 60g or so.


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PostPosted: Thu Dec 31, 2009 4:54 am 
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The battery module has some electronics built into it, so you would need to incorporate those (+waterproof the whole setup) if switching to a diff setup.


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PostPosted: Thu Dec 31, 2009 7:23 am 
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spartan wrote:
read this article. battery tech coming out in the next 4 years. electric cars should be a reality by 2015. interesting times we are living in.

http://www.greencarcongress.com/2009/12 ... .html#more


Erm, not to go too Off Topic (and I'll bring it back to the Di2 issue) - but electricity is NOT an energy source. It is a type of energy.
At this time, where does the majority of your electricity come from?
Petroleum powered (or built) plants.
Although it will be better to have a world where vehicular transportation does not emit toxic fumes and harm out environment, we will still have a issue with power. Solar and Wind power are the only possible, minimally petroleum-using-in-process, systems of energy gain. However, even those have issues (we can take this discussion into PM if you want. Or just watch the film "Collapse" as a break down of the concept)

Anyway, back on topic - as I talked with the friend of mine who is a Shimano tech rep, we both agreed that the next true step for electronic drivetrains would to have a system that powers the drivetrain's shifting mechanisms without the need for a large battery. Technology needs to be developed to efficiently utilize the energy we (humans) are expending while on the bike in the first place. You don't shift that often, hence you really don't need that much energy put towards the drivetrain constantly. ... that is what needs to be developed.

And Weight Weenies will then be quite happy, no? :)

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PostPosted: Thu Dec 31, 2009 9:31 am 
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prendrefeu wrote:
Anyway, back on topic - as I talked with the friend of mine who is a Shimano tech rep, we both agreed that the next true step for electronic drivetrains would to have a system that powers the drivetrain's shifting mechanisms without the need for a large battery. Technology needs to be developed to efficiently utilize the energy we (humans) are expending while on the bike in the first place. You don't shift that often, hence you really don't need that much energy put towards the drivetrain constantly. ... that is what needs to be developed.

Mavic's Mektronic had this. Batteries were used solely to transmit shifting requests to the mech. Shifting power came from the mech itself, via the top jockey wheel.


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PostPosted: Thu Dec 31, 2009 9:44 am 
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I've often thought that braking is overthought and under utilised on bikes. Ever look at that crazy European dude 's bike that he built from scratch with SPOON brakes?
Kinda nuts concept he had going (belt driven and spoon brakes) then I thought about modifications. A tiny interposable roller that spins on the tyre conecting it to friction block could work, but with more relevance to this thread....the roller could be a tiny strontium (or other rare earth) generator, with the first tiny pull of the brakes activating the generator with increasing drop in resistance (electrically) so it causes an increasingly higher mechanical resistance untill the friction blocks then come into play. Kinda a KERS system but without the extra 80HP. The initial reason why I was thinking about this is that it could be built very compact an could fit within the crown of the fork.

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PostPosted: Thu Dec 31, 2009 9:17 pm 
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Most electricity in the US (over 60%) comes from coal. Also, why not have regenerative braking? Have a very small battery and every time you use the the front brake a little wheel is spun by the tire. You could even adjust the wheel such that it engaged a mm before the actual brakes so you could coast to an intersection with the wheel making power and then apply the brakes firmly at the end.

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PostPosted: Thu Dec 31, 2009 9:27 pm 
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yourdaguy wrote:
Most electricity in the US (over 60%) comes from coal.


OT - this is incorrect. Coal accounts for just under 45%.
See fourth paragraph: http://www.eia.doe.gov/cneaf/electricit ... m_sum.html

In any case, thread seems to have drifted far off topic. Not much in the way of tuning opportunities w/Di2, it seems.


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PostPosted: Thu Dec 31, 2009 9:46 pm 
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Ok only 44% from coal but only 1% from petroleum.

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Posted: Thu Dec 31, 2009 9:46 pm 


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PostPosted: Thu Dec 31, 2009 9:52 pm 
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No offence intended but we already have a very efficiant way to transfer human energy to power both the "instructions" and the actual shifting. It's called a cable. Really guys. How complicated do you want to get. Remember K.I.S.S :beerchug:

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