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Dura Di2

Old 06-05-14, 09:48 AM
  #1  
lennyparis
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Dura Di2

How long does Dura Ace Di2 seat tube battery last?
Been keeping track of mileage and days between charges
And have been stretching that out but don't want to get stuck out on the road with no shifting
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Old 06-05-14, 09:53 AM
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Originally Posted by lennyparis View Post
How long does Dura Ace Di2 seat tube battery last?
Been keeping track of mileage and days between charges
And have been stretching that out but don't want to get stuck out on the road with no shifting
I have the frame mounted battery so I can't speak to the seat tube battery.

Yesterday was my 1st ride with my Shimano D-Fly that reads the Di2 battery levels. I went on a 40 mile ride that started on a fresh charge. After the ride it read 95%. Since it only reads in 5% increments, I could very well be at 91% and not know it.

I've yet to nail down an amount of time that the battery lasts.

As far as getting suck, the Di2 will shut down the FD shifting long before the battery dies. This will allow you to limp home with full use of the RD.
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Old 06-05-14, 01:32 PM
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Why tempt fate? Just charge it up every 1000 miles or so and don't think twice about it.
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Old 06-05-14, 01:37 PM
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Originally Posted by gc3 View Post
Why tempt fate? Just charge it up every 1000 miles or so and don't think twice about it.
40 miles relate to 5% as a 100% (flat battery) will relate to 800 miles based on the second post, so probably recharge a bit sooner.
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Old 06-05-14, 01:50 PM
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Maybe so, but without too much trouble you'll find from internet searching that a suggested average is 1000 miles, depending on riding / shifting style. I've personally experienced well over that number. Whatever, doesn't matter. Just pick what you think is a conservative enough number and remember to recharge when you get close.
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Old 06-05-14, 01:59 PM
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Originally Posted by ColnagoC40 View Post
40 miles relate to 5% as a 100% (flat battery) will relate to 800 miles based on the second post, so probably recharge a bit sooner.
I think it would be dependent on how much shifting your typical ride requires, though it seems most folks average about 1000mi out of a single charge. I've got 612 miles on mine and it hasn't started to give the 50% indicator when checked.
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Old 06-05-14, 02:29 PM
  #7  
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I had the frame mounted battery and now have a seat tube battery and haven't noticed any difference in longevity of charge. I think I get the flashing green light at a little over 1,100 miles.
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Old 06-05-14, 09:01 PM
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Originally Posted by ColnagoC40 View Post
40 miles relate to 5% as a 100% (flat battery) will relate to 800 miles based on the second post, so probably recharge a bit sooner.
Batteries discharge logarithmically, not linearly.

Let's do the math, shall we?

To approximate the batteries discharge profile, we take raqball's ride as an initial condition (5% drain after 40 mi). Assuming his shifting behavior is consistent throughout his ride, that would give us 2336.159 mi to a 95% drained battery (no, you can't get down 0%).

The 1000 mi guideline would give us a 72.261% drain (27.739% remaining).

Originally Posted by Nebby10 View Post
I've got 612 miles on mine and it hasn't started to give the 50% indicator when checked.
Your 612 mi ride gives 45.621% (54.388% remaining) based on the math, so it's pretty consistent

Originally Posted by raqball View Post
As far as getting suck, the Di2 will shut down the FD shifting long before the battery dies. This will allow you to limp home with full use of the RD.
I assume the FD requires more current to swing the cage (longer throw) compared to the RD so it is the first one to go.
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Old 06-05-14, 09:35 PM
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Originally Posted by e_guevara View Post
Batteries discharge logarithmically, not linearly.

Let's do the math, shall we?

To approximate the batteries discharge profile, we take raqball's ride as an initial condition (5% drain after 40 mi). Assuming his shifting behavior is consistent throughout his ride, that would give us 2336.159 mi to a 95% drained battery (no, you can't get down 0%).

The 1000 mi guideline would give us a 72.261% drain (27.739% remaining).



Your 612 mi ride gives 45.621% (54.388% remaining) based on the math, so it's pretty consistent



I assume the FD requires more current to swing the cage (longer throw) compared to the RD so it is the first one to go.
Now my head hurts..

I went 38 miles today and my battery is still reading 95% according to my D Fly. Now like I said before the D Fly only reads in 5% increments so I suppose I could be at 90.1% and the next shift will change my reading to 90% battery..

Todays 38 mile ride showed the following shifts:

FD: 4
RD: 96

Yesterdays 40 mile ride showed the following shifts:

FD: 4
RD: 179

Lots of city miles and climbs.. Either that or I am a shifting machine! LOL

Last edited by raqball; 06-05-14 at 09:40 PM.
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Old 06-05-14, 09:53 PM
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Originally Posted by raqball View Post
I went 38 miles today and my battery is still reading 95% according to my D Fly. Now like I said before the D Fly only reads in 5% increments so I suppose I could be at 90.1% and the next shift will change my reading to 90% battery..
Close... After 78 miles, the math says it's at 90.482%
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Old 06-05-14, 10:55 PM
  #11  
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Originally Posted by raqball View Post
Now my head hurts..

I went 38 miles today and my battery is still reading 95% according to my D Fly. Now like I said before the D Fly only reads in 5% increments so I suppose I could be at 90.1% and the next shift will change my reading to 90% battery..

Todays 38 mile ride showed the following shifts:

FD: 4
RD: 96

Yesterdays 40 mile ride showed the following shifts:

FD: 4
RD: 179

Lots of city miles and climbs.. Either that or I am a shifting machine! LOL
where can you see this data on how many shifts you do?
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Old 06-05-14, 11:21 PM
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Shimano introduced a new add-on (Feb 2014) to Di2 that allows one to monitor his/her rides.

Shimano Offers Di2 Wireless Connectivity with D-Fly .

Very nifty piece of tech. Before D-Fly, users only had distance as a metric to go on as far as battery life is concerned.

Using distance as a metric is next to useless IMO, as the battery gets drained only when used (shifting, neglecting self-drain). If one hardly shifts (i.e relatively flat terrain) then the battery lasts a whole lot longer than one who constantly shifts (either climbing or cycling inside a peloton). Having the shift data available makes for a more accurate drain profile than what I proposed several posts before.

Last edited by e_guevara; 06-05-14 at 11:30 PM.
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Old 06-05-14, 11:26 PM
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Ya i have dongle and a garmin 1000 was just curious where i see this
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Old 06-05-14, 11:28 PM
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The transmitter is great. Love seeing battery life on di2
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Old 06-06-14, 01:28 AM
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Originally Posted by raqball View Post
Todays 38 mile ride showed the following shifts:

FD: 4
RD: 96

Yesterdays 40 mile ride showed the following shifts:

FD: 4
RD: 179
Originally Posted by coppercook62 View Post
Ya i have dongle and a garmin 1000 was just curious where i see this
Yeah, I was wondering about that too. Looked all over the manual but couldn't find where it is. Maybe he counted it manually?

It would really be nice to know where this can be found.
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Old 06-06-14, 05:15 AM
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Digging around the web I found this on DC Rainmaker's In-Depth Review of the Garmin Edge 1000. Skip to the Shimano Di2 Support section.



So this is the only way to track the number of shifts on Di2 (for now).
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Old 06-06-14, 05:36 AM
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Originally Posted by raqball View Post
Todays 38 mile ride showed the following shifts:

FD: 4
RD: 96

Yesterdays 40 mile ride showed the following shifts:

FD: 4
RD: 179
Are the shifts you indicated "per ride" (reset to zero at the start of the ride), or is that the "total" since recharging?
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Old 06-06-14, 06:30 AM
  #18  
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Originally Posted by e_guevara View Post
Batteries discharge logarithmically, not linearly.

Let's do the math, shall we?

To approximate the batteries discharge profile, we take raqball's ride as an initial condition (5% drain after 40 mi). Assuming his shifting behavior is consistent throughout his ride, that would give us 2336.159 mi to a 95% drained battery (no, you can't get down 0%).

The 1000 mi guideline would give us a 72.261% drain (27.739% remaining).



Your 612 mi ride gives 45.621% (54.388% remaining) based on the math, so it's pretty consistent



I assume the FD requires more current to swing the cage (longer throw) compared to the RD so it is the first one to go.
Never looked at this before, but if one wants to be accurate, I guess a flat linear curve approach, will be more accurate than logarithmic. We are probably high-jacking the thread, but I took an interest in your math. Temperature would also have an effect.

From research as per the linky below, scroll down to the graph. It looks like a simple linear calculation, based on a flat voltage curve in the usable discharge range will yield a more practical estimation than going logarithmic. Then, in practice a hilly course using lots of gear changes will again change the whole situation.

The battery is Lithium Ion, I believe.

Lithium-based Batteries Information ? Battery University

In the end, real experience in the field as per the other posts here has probably provided all the answers we need.
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Old 06-06-14, 08:07 AM
  #19  
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Originally Posted by coppercook62 View Post
where can you see this data on how many shifts you do?
Originally Posted by coppercook62 View Post
Ya i have dongle and a garmin 1000 was just curious where i see this
Originally Posted by e_guevara View Post
Yeah, I was wondering about that too. Looked all over the manual but couldn't find where it is. Maybe he counted it manually?

It would really be nice to know where this can be found.
The only place it's displayed is on the Garmin unit itself. The shift data does not make it's way into Garmin Connect or any other website that you upload the ride to..

On the Edge, you go to your ride history then select the ride. Scroll all the way down through the ride stats and eventually you will get to the shift data..

Originally Posted by e_guevara View Post
Digging around the web I found this on DC Rainmaker's In-Depth Review of the Garmin Edge 1000. Skip to the Shimano Di2 Support section.



So this is the only way to track the number of shifts on Di2 (for now).
Yup, that's it..

Originally Posted by e_guevara View Post
Are the shifts you indicated "per ride" (reset to zero at the start of the ride), or is that the "total" since recharging?
The number of shifts displayed are for that ride..
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Old 06-06-14, 08:29 AM
  #20  
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Originally Posted by Nebby10 View Post
I think it would be dependent on how much shifting your typical ride requires

^^^This. You can get >10,000 miles out of a single charge if you never shift gears.
Battery life is entirely dependent on # of shifts, not # of miles rideen.


Originally Posted by Nebby10 View Post
I've got 612 miles on mine and it hasn't started to give the 50% indicator when checked.
Not sure how consistent this behavior is, but fwiw my wife's system was giving her the 50% indicator for several rides (4 or 5, maybe ~250 miles total) and then suddenly in the middle of that 4th or 5th ride it went into Battery Low, Disable Front Derailleur mode. iow, the transition from 50% to <25% seemed to come on very suddenly.
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Old 06-06-14, 08:39 AM
  #21  
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Originally Posted by ColnagoC40 View Post
We are probably high-jacking the thread
I don't believe we are hijacking the thread. This discussion is about battery life (of Di2) and this just adds more information for everybody about how batteries work.

The battery is Lithium Ion, I believe.
The material used doesn't change the physics of charge movement. The material's properties changes the rate at which charges are exchanged, but it will always be logarithmic.

... but if one wants to be accurate, I guess a flat linear curve approach, will be more accurate than logarithmic.
No.

From research as per the linky below, scroll down to the graph. It looks like a simple linear calculation, based on a flat voltage curve in the usable discharge range will yield a more practical estimation than going logarithmic.
Li-Ion batteries have a usable voltage of 4.2 V - 2.7 V (100% - 63%). During charging, the fastest increase happens from 0% up to 63%. To get to 99.97% takes four times the duration to charge to 63%. The reverse is true during discharging. This follows a logarithmic behavior.

The 100% to 63% discharge profile can be approximated using linearization. The materials used in newer Li-Ion batteries makes the discharge slower, which approximates a line rather than a logarithmic curve. But the behavior is still logarithmic.


Then, in practice a hilly course using lots of gear changes will again change the whole situation.
In the end, real experience in the field as per the other posts here has probably provided all the answers we need.
I've noted previously that the battery only discharges when you shift (neglecting self-discharge and temperature effects). Every time you shift discharges the battery. Having distance as a metric for battery life is next to useless. Experience in the field has only given us that.

NOTE: Since Li-Ion batteries must not go below 2.7 V (or chemical change in the battery occurs), a protection circuit in the battery prevents any further discharge. This lower limit is the practical limit in the battery's usable voltage, thus 4.2 V (100%) to 2.7 V (0%) as reflected in the Di2 indicator.
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Old 06-06-14, 08:55 AM
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Originally Posted by Bob Ross View Post
^^^This. You can get >10,000 miles out of a single charge if you never shift gears.
Battery life is entirely dependent on # of shifts, not # of miles ridden.
Yes and FD shifts take more umph than the RD..


Not sure how consistent this behavior is, but fwiw my wife's system was giving her the 50% indicator for several rides (4 or 5, maybe ~250 miles total) and then suddenly in the middle of that 4th or 5th ride it went into Battery Low, Disable Front Derailleur mode. iow, the transition from 50% to <25% seemed to come on very suddenly.
When I took my system in to get the firmware update I was told my battery was almost dead. Oddly, I had just charged it about a week before that.

I am going to keep a close eye on it now that I have the battery level displayed..

Last edited by raqball; 06-06-14 at 08:58 AM.
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Old 06-06-14, 08:57 AM
  #23  
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Originally Posted by e_guevara View Post
Batteries discharge logarithmically, not linearly.

Let's do the math, shall we?

To approximate the batteries discharge profile, we take raqball's ride as an initial condition (5% drain after 40 mi). Assuming his shifting behavior is consistent throughout his ride, that would give us 2336.159 mi to a 95% drained battery (no, you can't get down 0%).

The 1000 mi guideline would give us a 72.261% drain (27.739% remaining).

Your 612 mi ride gives 45.621% (54.388% remaining) based on the math, so it's pretty consistent

I assume the FD requires more current to swing the cage (longer throw) compared to the RD so it is the first one to go.
IMO there's too simply many variables to try to figure out battery level based on math, let alone to the precision of the numbers you're throwing out.
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Old 06-06-14, 09:24 AM
  #24  
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Originally Posted by Nebby10 View Post
IMO there's too simply many variables to try to figure out battery level based on math, let alone to the precision of the numbers you're throwing out.
Until now we have no other metric than distance, and I guess everyone agrees that the number of shifts is more relevant in figuring out the remaining battery level. I agree that there are too many variables (FD current drain per shift, RD current drain per shift, temperature, self-discharge), but the derailleur drain is the most significant in the discussion. Effects of temperature and self-discharge are too small and can be considered negligible.

Notice that I did say "approximate" and "assuming his shifting behavior is consistent..." in my post, and it doesn't help that the D-Fly only reports battery life in 5% decrements. The values I presented are merely approximates based on one sample (raqball's ride) using a known verifiable phenomenon (logarithmic discharge behavior of batteries) and assuming a value for an unknown variable (number of shifts).

Regarding the precision of the figures, FYI, e (the natural logarithm), is an irrational number. Using it in computation will always result in a number with a fractional part. Truncating the results to 3 decimal places was an arbitrary choice. It will not matter if I omitted (or included) the fractional part since it's only an approximation.
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Old 06-06-14, 09:51 AM
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Originally Posted by e_guevara View Post
Until now we have no other metric than distance, and I guess everyone agrees that the number of shifts is more relevant in figuring out the remaining battery level. I agree that there are too many variables (FD current drain per shift, RD current drain per shift, temperature, self-discharge), but the derailleur drain is the most significant in the discussion. Effects of temperature and self-discharge are too small and can be considered negligible.

Notice that I did say "approximate" and "assuming his shifting behavior is consistent..." in my post, and it doesn't help that the D-Fly only reports battery life in 5% decrements. The values I presented are merely approximates based on one sample (raqball's ride) using a known verifiable phenomenon (logarithmic discharge behavior of batteries) and assuming a value for an unknown variable (number of shifts).
I just don't see the point of "doing the math" due to the numerous variables, small sample size, and the lack of verification due to the 5% limitation to the D-Fly (or for everyone without D-Fly, a 50% limitation for the earliest indication). It's possibly an interesting exercise in math, but I'd say it's almost off topic to this thread. Also, it's probably an edge case, but the temperature effect is actually a fairly massive factor for winter rides.
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