Nerdy Di2 Battery question

Discuss light weight issues concerning road bikes & parts.
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cyclespeed
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Joined: Mon Jun 06, 2016 8:45 am

by cyclespeed

Not massively important, but occasionally I forget to charge my Di2 and I get a low battery warning from my Garmin.

If I´m some way from home and it's hilly, and I need to save battery, what is the most economical way to shift gear?

i.e. is it better to shift 3 on the cassette than go to the big ring? How much more juice does a FD shift use than a RD shift? Is up the same as down? Questions, questions....

Stueys
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Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

I'm guessing so take this with a pinch of salt, but think Shimano kill the FD first. Using that logic I'd stay off the FD and shift on the back to conserve juice. Seems logical given the FD motor is the biggie.

hogehoge
Posts: 51
Joined: Mon Feb 25, 2013 11:59 pm

by hogehoge

You can add a field to the Garmin to display the remaining di2 battery percentage I think. Then you know to re-charge well before low battery warning.

gorkypl
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Joined: Fri Sep 21, 2018 9:31 am
Location: Poland

by gorkypl

FD uses more power, as it operates on chain under tension. After FD no longer can operate, there is still plenty of battery left for RD.
I'd also guess downshifting (moving to bigger cogs) on the rear takes more energy, as in Di2 there is a spring too (like in mechanical RDs).

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cyclespeed
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by cyclespeed

I think it's clear that the FD uses more than the RD, but how much more...?

Like if there's some flat between 2 uphills, is it better to shift down 3 on the cassette or just move up on the front? These questions keep me awake at night!!

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Calnago
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by Calnago

cyclespeed wrote:I think it's clear that the FD uses more than the RD, but how much more...?

Like if there's some flat between 2 uphills, is it better to shift down 3 on the cassette or just move up on the front? These questions keep me awake at night!!
You’d sleep like a baby with a mechanical drive train Image.
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gorkypl
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Location: Poland

by gorkypl

cyclespeed wrote:
Fri Oct 11, 2019 10:05 am
I think it's clear that the FD uses more than the RD, but how much more...?

Like if there's some flat between 2 uphills, is it better to shift down 3 on the cassette or just move up on the front? These questions keep me awake at night!!
Much more.
When I was riding Di2, when battery was dying, the last available movement of FD was really slow and 'weak', but a lot (several dozens at least) of 'normal' RD moves were still available afterwards. So I'd say it's always better to shift RD in situations with little battery left.

BTW, if you got the low battery warning but never got to the point when FD stopped moving, then I'd say the battery was not realy THAT low.

And, as a side note, this spring I moved from Di2 to mechanical Record 12 and I'm not really looking back. Most of the times at least ;)

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ms6073
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by ms6073

cyclespeed wrote:
Fri Oct 11, 2019 10:05 am
I think it's clear that the FD uses more than the RD, but how much more...?
I may be wrong but as I don't have the BT interface on our bikes, but thought that the when the low battery prompt was displayed on a Garmin, the battery reserves were at or below 7% and the warning is to indicate that Di2 has already started inhibiting signals to the front derailleur.
Michael - The Anaerobic Threshold is neither...

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Dan Gerous
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Joined: Sun Aug 12, 2007 6:28 pm

by Dan Gerous

Calnago wrote:
Fri Oct 11, 2019 11:44 am
cyclespeed wrote:I think it's clear that the FD uses more than the RD, but how much more...?

Like if there's some flat between 2 uphills, is it better to shift down 3 on the cassette or just move up on the front? These questions keep me awake at night!!
You’d sleep like a baby with a mechanical drive train Image.
:mrgreen:

Stueys
Posts: 408
Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

Dan Gerous wrote:
Fri Oct 11, 2019 5:44 pm
Calnago wrote:
Fri Oct 11, 2019 11:44 am
cyclespeed wrote:I think it's clear that the FD uses more than the RD, but how much more...?

Like if there's some flat between 2 uphills, is it better to shift down 3 on the cassette or just move up on the front? These questions keep me awake at night!!
You’d sleep like a baby with a mechanical drive train Image.
:mrgreen:
Or charge at 50%......

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Dan Gerous
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Joined: Sun Aug 12, 2007 6:28 pm

by Dan Gerous

Seriously though, the solution is quite simple. Everytime you lay in bed not sleeping and thinking about it, just get up and plug the Di2 charger. Sweet dreams!

RussellS
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Joined: Wed Feb 03, 2010 1:31 am

by RussellS

cyclespeed wrote:
Fri Oct 11, 2019 9:13 am
Not massively important, but occasionally I forget to charge my Di2
Sometimes I forget to charge my 7970 Di2 battery. Every fall I wonder if I should recharge. I like to recharge every two years. So every fall I wonder did I recharge last year or has it been two years and its now time to recharge. And if I recharge after two years, I wonder if I'm wearing the battery out by charging it too much. Should I wait three years to recharge instead of overcharging at only two years interval. Its terrible living with a battery operated electrical shifting bicycle. I suspect the mechanical shifting people replace cables more often than I recharge my battery.

velov
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Joined: Fri Apr 20, 2018 9:09 am

by velov

RussellS wrote:
Fri Oct 11, 2019 11:19 pm
cyclespeed wrote:
Fri Oct 11, 2019 9:13 am
Not massively important, but occasionally I forget to charge my Di2
Sometimes I forget to charge my 7970 Di2 battery. Every fall I wonder if I should recharge. I like to recharge every two years. So every fall I wonder did I recharge last year or has it been two years and its now time to recharge. And if I recharge after two years, I wonder if I'm wearing the battery out by charging it too much. Should I wait three years to recharge instead of overcharging at only two years interval. Its terrible living with a battery operated electrical shifting bicycle. I suspect the mechanical shifting people replace cables more often than I recharge my battery.
Every two years? Do you even change gears at all?
You're overthiking the charge cycles...batteries these days aren't that precious.

bilwit
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Joined: Sun Apr 03, 2016 5:49 am
Location: Seattle, WA

by bilwit

velov wrote:
Sat Oct 12, 2019 1:16 am
Every two years? Do you even change gears at all?
You're overthiking the charge cycles...batteries these days aren't that precious.
unless they're $1000 phones that are designed that way :lol:

icantaffordcycling
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Joined: Wed Jan 09, 2019 5:03 am

by icantaffordcycling

What is an extra di2 battery if you are already carrying a spare tubular anyways. context

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