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DIY DI2

Discussion on bikes, and whatever...

Re: DIY DI2

Postby maxxevv » Mon Jan 02, 2012 6:03 pm

Hey Jeff ... that's why I called those connectors 'pesky' ... :lol:

Without a production of about 500pcs, it sure doesn't make sense to produce them.

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Re: DIY DI2

Postby ToddC » Fri Jan 06, 2012 6:26 am

I am thinking about removing my DI2 Battery set up and going internal with it. Currently the battery is under the bottom bracket (clean install already thanks to Trek). I have a 2010 6 series Madone with 7500 miles on the DI2 with zero issues. I am thinking about doing this mod for two reasons. Even cleaner install and probably about 2 oz. weight savings. I do have quite a bit of knowlege with Lipoly batteries from all my yrs. flying model airplanes.Thunder Power has a pack I'm thinking about. 480mah 2 cell @ 28 grams or I could go fly weight with the 250mah @ 18 grams. I already own a Thunder Power balancer and a high end charger with adjustable mah output so no cost there. Does anyone know at what voltage the 50% green blinking light turns on? Or better yet when the 25% red light turns on?

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Re: DIY DI2

Postby pritchet74 » Fri Jan 06, 2012 6:44 am

No idea about the voltage. I haven't checked it at various charge levels, but the battery level light still works when installing a different battery. I honestly can't ever imagine going back to using the standard Shimano battery. Having it hidden in the seat post is the only way to go. I have a reminder in my iPhone to tell me to charge my battery every 2 months.
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Re: DIY DI2

Postby Jeffr » Fri Jan 06, 2012 6:51 am

lipo and lion have different discharge characteristics. I don't know which di2 is, I honestly haven't looked very closely at the battery. lipo will only have about a 1v swing from 100% charge to nearly fully discharged. You can probably find a manufacturer's datasheet for the cells in your pack to determine the right thresholds. Obviously shimano has hard coded it for the batteries they use but other batteries within the same family should have the same charge/voltage curve even with greater capacity.
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Re: DIY DI2

Postby ToddC » Fri Jan 06, 2012 7:12 am

Jeffr wrote:lipo and lion have different discharge characteristics. I don't know which di2 is, I honestly haven't looked very closely at the battery. lipo will only have about a 1v swing from 100% charge to nearly fully discharged. You can probably find a manufacturer's datasheet for the cells in your pack to determine the right thresholds. Obviously shimano has hard coded it for the batteries they use but other batteries within the same family should have the same charge/voltage curve even with greater capacity.


Thanks for the reply.
The Shimano battery is a Lithium ion. The aftermarket battery is a Lithium polymer. Full charge on the Lipoly is 4.2v per cell. I don't run them below 3.5 volts per cell. This is why I need to know this or I will test for myself if someone can't supply it. Running these cells too low can cause an imbalance and on the next charge very bad things can happen.
Last edited by ToddC on Fri Jan 06, 2012 7:20 am, edited 1 time in total.
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Re: DIY DI2

Postby ToddC » Fri Jan 06, 2012 7:19 am

pritchet74 wrote:No idea about the voltage. I haven't checked it at various charge levels, but the battery level light still works when installing a different battery. I honestly can't ever imagine going back to using the standard Shimano battery. Having it hidden in the seat post is the only way to go. I have a reminder in my iPhone to tell me to charge my battery every 2 months.


Thanks for the reply. I haven't decided if I want to go in the post or in the seat tube, down tube, etc... If you are using a Lipoly knowing the voltage is paramount. Just found your post with the new battery set up. You didn't mention balancing these cells in your post. Before soldering these cells together all of the voltages should be pulled together within a few hundredths of a volt. After assembly a balancer should be used at least on the first charge cycle.
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Re: DIY DI2

Postby Jeffr » Fri Jan 06, 2012 8:00 am

You should probably consider the halfway point as time to recharge a lipo.

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Re: DIY DI2

Postby Oilman » Fri Jan 06, 2012 10:13 am

I've measured the borders battery charge indicator last year:
>7.6V: Green led 2s (100% according to Shimano)
≤7.5V: Greens led flashes 5x (50% according to Shimano)
≤7.0V: Red led 2s (25% ...)
≤6.0V: Red led flashes (0%)

The front derailleur stops working when the voltage comes below 6.8V. The rear-derailleur works fine when the voltage is above 6.2V, when it drops below 6.2V you can get it shift but it isn't shifting smoothly anymore.

When the graphs posted by Jeffr are also valid for your Lipo battery you should charge the battery when the green leds start flashing. When you'll wait till the red led comes on, you're too late.
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Re: DIY DI2

Postby ToddC » Fri Jan 06, 2012 4:16 pm

Oilman wrote:I've measured the borders battery charge indicator last year:
>7.6V: Green led 2s (100% according to Shimano)
≤7.5V: Greens led flashes 5x (50% according to Shimano)
≤7.0V: Red led 2s (25% ...)
≤6.0V: Red led flashes (0%)

The front derailleur stops working when the voltage comes below 6.8V. The rear-derailleur works fine when the voltage is above 6.2V, when it drops below 6.2V you can get it shift but it isn't shifting smoothly anymore.

When the graphs posted by Jeffr are also valid for your Lipo battery you should charge the battery when the green leds start flashing. When you'll wait till the red led comes on, you're too late.


Thanks you guys! I didn't want to come off too conservative but 3.75v per cell has always been the target. On a 2 cell 7.50v would be the number. I am going to proceed with the project and update when complete. I will be checking battery voltage routinely as it comes down to confirm the green light flashes on time.
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Re: DIY DI2

Postby pritchet74 » Fri Jan 06, 2012 8:23 pm

ToddC wrote:
pritchet74 wrote:No idea about the voltage. I haven't checked it at various charge levels, but the battery level light still works when installing a different battery. I honestly can't ever imagine going back to using the standard Shimano battery. Having it hidden in the seat post is the only way to go. I have a reminder in my iPhone to tell me to charge my battery every 2 months.


Thanks for the reply. I haven't decided if I want to go in the post or in the seat tube, down tube, etc... If you are using a Lipoly knowing the voltage is paramount. Just found your post with the new battery set up. You didn't mention balancing these cells in your post. Before soldering these cells together all of the voltages should be pulled together within a few hundredths of a volt. After assembly a balancer should be used at least on the first charge cycle.


Ya, I am just a guy with a soldering iron. This isn't something I even thought about. If I put another battery pack together I will check it out though.
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Re: DIY DI2

Postby nathasm » Wed Jan 25, 2012 3:19 pm

So I tried going with an internal battery and purchased: http://www.batteriesinaflash.com/airsoft-batteries-chargers/li-po-airsoft-batteries/airsoft-battery-lipo-7-4v-1200mah-20c-short-stick-mini-tamiya

Essentially I cut the wire going to the battery holder (from an internal wiring kit), soldered the two red wires together and then again for the two black. Soldered those to some 18 AWG wire to a mini-tamaya plug. I ended up frying both my front and rear derailleur. My connections appeared secure and there was heat shrink around all the exposed wires.

I luckily was able to get them warrantied, but I'm worried about giving it a second go. Was it the use of a LiPo battery that would have caused this? I'm looking at this LIon http://www.batteryspace.com/customizedpack14430x2endbyend72vli-ion600mah432whbatterywithpcb.aspx instead of going LiPo.
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Re: DIY DI2

Postby pritchet74 » Wed Jan 25, 2012 5:52 pm

Wow. I am shocked you got them warrantied. And also shocked that you fried them parts.
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Re: DIY DI2

Postby nathasm » Wed Jan 25, 2012 7:39 pm

pritchet74 wrote:Wow. I am shocked you got them warrantied. And also shocked that you fried them parts.


I know I'm lucky, that's why I'm hesitant to try again.

But if what I wrote sounds correct and the battery choice is correct, then I'll probably give it another go.
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Re: DIY DI2

Postby pritchet74 » Wed Jan 25, 2012 7:41 pm

I can only recommend the battery setup that I used since I haven't had any problems with it.
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Re: DIY DI2

Postby Oilman » Thu Jan 26, 2012 9:52 am

nathasm wrote:
pritchet74 wrote:Wow. I am shocked you got them warrantied. And also shocked that you fried them parts.


I know I'm lucky, that's why I'm hesitant to try again.

But if what I wrote sounds correct and the battery choice is correct, then I'll probably give it another go.


The battery should be fine, although the capacity is a bit of over-kill for DI2. What worries me is that you'd got it completely wrong the first time, so what are you going to do different the second time?
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