Fried DA Di2

Discuss light weight issues concerning road bikes & parts.
Posts: 64
Joined: Mon Mar 05, 2012 1:36 am

by borja


Here I've got a bike with DuraAce Di2 with custom battery which has been connected with reversed polarity. Di2 dead.

Now I want to check the damage. The junction box seems ok since it flashes the LEDs (and reports a system error).
Both deraileurs dont work.
I plan to unmount the deraileurs from the bike and put them on another Di2 bike to see if the deraileurs work.

My question is if this is a safe thing to do or there is any risk of damaging the working Di2 on another bike if I connect the fried deraileur on it?
I'm pretty sure that the FD is fried because it gets warm if I connect it to the battery.

Any thoughts would be welcome.


by Weenie

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by Omiar

It should be safe because RD and FD only carry out instructions received from the shifters and they send any power to the system as the battery does.
Try the RD on another bike first, if it works, try the FD next. I think you're right that the problem is in the FD.
Scott Foil Ultegra Di2
Scott Scale 35 26"
Scott Spark LTD 29" M8000

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by kulivontot

Power is always delivered from the battery. Shifters just communicate with the microcontroller. Take it to a shop with the di2 diagnostic kit and they can diagnose it.

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by gregalfa

I think it should be ok. it has happened to me twice. Both FD and RD still working just perfect.
The Great CarboniO

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by borja

Ok thanks!
I'll try to get a diag kit, otherwise I'll take a risk and connect the deraileurs to another bike.
Im 99% sure that the FD is finished.

Does the Di2 system operate with only one deraileur connected?

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by WeightySteve


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by borja

S**t. Then both are dead.


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by HammerTime2

In German Technology (Shimano Electronic/Aero integration), LegalizeMyCAAD9 wrote:If the official Shimano electronic is Di2, then this is the DIY2 groupset :)
And this is the DITY2* groupset**

* Do it to yourself

** Perhaps WW shows a biased sample of do it yourself projects or modifications in which the results are favorable, as those with unfavorable experiences are less likely to post about them, whether through embarrassment or having crashed and not being around to post. Failures are often more instructive than successes.

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by borja

Well, this one is a definite FAIL. But this is a fail because the manufacturer of the baterry has reversed the wires in the originally suplied connector. See pic. ... 5715680002

So, if somebody is going to play with custom bateries remember : DO NOT REVERSE THE POLARITY, there is NO PROTECTION on the Di2.

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by sharkman

I'm not completely certain if it also works with reverse polarity but I allready experienced that di2 has a crash mode that puts the front and rear mech out of order.
You'll need a shimano device to reset both to normal working order (off course this will only work if nothing is damaged).
(I hooked both front and rear mech to another di-2 bike and this does also do the trick).

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by borja

I have tried to put the FD and RD to another bike and they dont work so they are damaged..
The front box just blinks the red LED

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by Thirstyman

threads like this remind me why I like simple bikes

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by borja

:)) Thirstyman you're right;)

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Location: Gaithersburg, Maryland

by 1spd

Man I know little to nothing about Di2 and ESP other than having ridden both of them. That being said, I love my mechanical set up if only for that reason alone! Don't get me wrong, if I had the money, I would have ESP (as well as a mechanical SR set up as well!).
Cannondale Synapse (alu) works

by Weenie

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Joined: Mon Mar 05, 2012 1:36 am

by borja

I agree with you. On eurobike I have tried the new DA. I might be wrong but the mech version seems to work better than Di2.

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