When first got my Di2 two years ago I could go months or several thousand miles between charges. But now the battery only last several hundred miles. Does this sound reasonable?

You must be riding a lot more slowly or going up and down hills a lot more often. Or is this supposed to be a Duracell vs Energizer kinda thread?

Batteries wear out. Lithium Ion after about three years start to lose capacity, no matter what you do. New Battery time.

That sounds unusual as you would have very few charge cycles on the battery. Unfortunately, being out in the hot sun is very hard on a lithium battery. How long is the warranty?

Two years from the time of purchase.

No matter how many cycles on it Li-Ion start to lose capacity after about three years. This battery could have been stored for a year or more before the sale.

I would ask for a warranty replacement.

edit: Something else to consider, it's not uncommon for the fuel gauge on a lithium battery to get out of calibration, particularly for products that don't go through a full charge discharge cycle very often. One thing to try would be to fully drain the battery before your next charge. I know I've recovered 30-40% of my laptop battery capacity just by running it through a calibration cycle.

Depends on the quality of cells and how it's been stored. There's nothing magic about three years.

About a year ago or so, I went from about 1,500 miles per charge down to about 500 miles per charge. I thought my battery was just dying a slow death. But it ended up that one of my derailleurs just needed cleaning. My mechanic said that he sees that a lot around here (we live on the coast). Anyway, after cleaning, the battery cycle went up to about 1,200 miles per charge.

Makes you wonder then how this tech is surviving on CX bikes.

They are starting to rely on "electricity" vs tedious manual cable pulling!

You didn't just add the Bluetooth module did you?

I have two Di2 bikes with D-fly and they seem to reduce battery life by 10-20%. I think there have been some firmware updates related to battery management.

D-fly does drop time between charges a bit. I have the better part of 20,000 miles on an internal battery and it is still going strong.

From the Shimano on line dealer manual:

SHIMANO Dealer's Manual / User's Manual

Lithium ion battery

••Lithium-ion batteries are recyclable, valuable resources.

For information on used batteries, contact the place of purchase or a bicycle dealer.

••Charging can be carried out at any time regardless of the amount of charge remaining. Always be sure to use the special battery charger to charge the battery until it is fully recharged.

••The battery is not fully charged at the time of purchase. Before riding, be sure to fully charge the battery.

••If the battery has become completely empty, charge it as soon as possible. If you leave the battery without charging it, it will cause the battery to deteriorate.

••The battery is an exhaustible item. The battery will gradually lose its capacity to charging after repeated use. If the length of time that the battery can be used becomes extremely short, it has probably reached the end of its life, and so you will need to purchase a new battery.

••The life of the battery will vary depending on factors such as the storage method, the usage conditions, the surrounding environment and the characteristics of the individual battery pack.

••If storing the battery away for a long period, remove it when the battery level is 50% or higher or when the green indicator is illuminating in order to prolong its useful life; and it is recommended that you charge the battery about every six months.

••If the storage temperature is high, the performance of the battery is reduced, and its useable time will be shorter. When you use the battery after a long storage period, store the battery indoors where the battery will not be exposed to direct sunlight or rain.

••If the ambient temperature is low, the battery's usable time will be shorter.

Did add di fly so that is part of the issue
Will also try to drain battery and then recharge (just don't want to get stuck out on the road stuck in one gear)

Geee, I didn't see this coming....

What's next? Servos wearing out? Circuit boards going haywire/dying? Nah...it'll never happen.....

I wanna see how far those $70K Teslas will be going in two or three years.....

Now [all together] let's all be early adopters of delicate cutting-edge technology! (And pay a premium for the privilege)

Hey, just wait till the battries start assploding ona hot day and melding with the goo from your assploded CF frame, forming a monster-green disembodied arm and hand that pulls you into the puddle of ooze created by molten gear!

Funny how anytime someone asks a service related question regarding electronic shifting the retrogrouches pop out of the weeds and shout "See We told you, it does suck!" On the other hand no similar reaction when someone asks about busted cables and all the other problems related to mechanical.

Probably a little soon, but not out of line. Li-ion dies from two things: Age and charge cycles. They start losing capacity pretty fast after about three years and it's a function of the chemistry. That's probably what's in play here. See if you can find a date code on the battery - they usually have the month and date encoded in a number. That's going to matter more than how long you've owned it. For example, if you bought the bike but the battery had been manufactured a year before you got the bike, then you'd be right on the schedule for it's aging issues.

The other thing is if you keep the bike out in the garage during the winter and it's freezing or getting really hot (or worse, both), you'll age the battery faster. There are methods for testing component life by accelerating the aging and they all involve temp cycles. So if you, say, live in a place where it gets really cold in the winter and your garage goes down below freezing, you are going to prematurely age the battery through freezing.

Either way, it's time for a new battery.

J.

Interesting note. Thanks.

I'm 54 years old, and have never had a cable break on me. Admittedly, i have replaced one that was starting to fray, in the last five years... hmmmmm $4 cable vs. $100 battery, yeah, hardly any difference there....

Thank you for your valuable, thought-provoking contribution.

What did you expect? You made no meaningful contribution what so ever to the thread. Nobody cares if your mechanical system has worked perfectly for 49 years straight. It has nothing to do with a Di2 battery.

This bears repeating.