# Ultegra Di2 battery life while not in use



## the mayor (Jul 8, 2004)

I'm picking up a Di2 bike and am wondering what people are getting from battery life while the bike is not being used?

I ask because sometimes my bike sits for a week or 2 because I'm riding my mtb or cross bikes.

Also thinking about getting an extra battery to have in my gear bag in case I space it and forget to charge the battery that's on the bike...so I'm wondering how long a spare battery will hold charge.

Thanks in advance!


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## r1lee (Jul 22, 2012)

Not needed and would totally be a waste of money. Ive had my bike for 2 months and have not had to do a single charge.

Even when your indicator glows red, you still have aout 8hrs of use remaining, from my recollection. I just pay attention to the lights before I take her out.


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## Sven_Nijs (Jul 14, 2011)

The only reason to buy a spare is if you're the kind of person to forget to put petrol in their car and run it dry despite the flashing & beeping warnings...


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## the mayor (Jul 8, 2004)

Sven_Nijs said:


> The only reason to buy a spare is if you're the kind of person to forget to put petrol in their car and run it dry despite the flashing & beeping warnings...


Well...that's why I have AAA 
But I don't think they'll come jump start my bicycle.
I just wanted to know what life time the battery got while not in use.
Like I said...I sometimes won't touch my road bike for a couple of weeks because of other bikes ( like cross bikes right now). I guess I'll just keep the battery topped.
Thanks for all your replies


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## eidolon (Jun 21, 2012)

If the are lithium batteries, they do not self-discharge when unused.


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## the mayor (Jul 8, 2004)

eidolon said:


> If the are lithium batteries, they do not self-discharge when unused.


Every thing discharges.....just depends on how fast.


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## eidolon (Jun 21, 2012)

the mayor said:


> Every thing discharges.....just depends on how fast.


Yeah, and if you want to be pedantic the sun will discharge in another five billion years.

The self discharge rate of lithium battery chemistry is about 1% per month (conservatively), so unless Di2 uses a constant trickle of electricity even when the bike is unused, a fully charged lithium pack will be able to sit around for years. If you want to dig into it a bit, there is more info here: Lithium-based Batteries Information

@ the OP: Getting an extra battery doesn't seem to be a terribly useful idea. If it's stored at 100% charge, it'll lose around 20% of its total storage capacity within 12 months. The ideal storage state for Li is 40% charge.

As others have suggested, just keep the one battery and pay attention to warning indicators.


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## the mayor (Jul 8, 2004)

Thank you for being more pedantic than I.
And thank you...and everyone else..for the info.


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## Cut.Aussie (Mar 19, 2011)

I have two Di2 equipped bikes, a Look and a new Cervelo which is my current ride of choice which gets to be ridden 2 or 3 times a week. The Look sits in the garage and only ridden maybe once or twice a month and the Shimano battery seems to hold up very well, I would not worry about self discharge.


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## the mayor (Jul 8, 2004)

Cut.Aussie said:


> I have two Di2 equipped bikes, a Look and a new Cervelo which is my current ride of choice which gets to be ridden 2 or 3 times a week. The Look sits in the garage and only ridden maybe once or twice a month and the Shimano battery seems to hold up very well, I would not worry about self discharge.


Thanks....I was looking for some real experience.
Now....if I could just get rid of this cold and it would stop raining:mad2:


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## vette (Feb 1, 2009)

the mayor said:


> Well...that's why I have AAA
> But I don't think they'll come jump start my bicycle.
> I just wanted to know what life time the battery got while not in use.
> Like I said...I sometimes won't touch my road bike for a couple of weeks because of other bikes ( like cross bikes right now). I guess I'll just keep the battery topped.
> Thanks for all your replies


Hmmm,idea AAA for Di-2 & EPS riders,$50 a year.


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