As it's slowly getting colder in the northern hemisphere you may be considering not using your bike for a while. Or just riding your turbo trainer - if you can get one. Or if you have multiple bikes, you'll probably keep your main bike indoors during the colder, harsher months and ride a somewhat less expensive bike.
If you do, it's important to take care of your Di2 battery and what to do before storing it. That way it is ready for you when you return to riding as the weather improves.
First: make sure your bike is clean
I'm not trying to be like every other "how to store your bike" page on the internet, BUT: cleaning your bike before storing it is really important. You've probably ridden it in the rain or through puddles when you last rode, so please make sure it's clean before storing it.
Especially if you plan on not using the bike for a couple of months. That means not only cleaning the dirt and mud of your bike, but also playing close attention to your drivechain.
Decide whether or not the cassette and chain are good for another couple of months and if they are, clean and dry them. I Also apply fresh lube to your chain and wipe off the excess.
If your chain is near the end of its life - see this CyclingTips article - I generally just order a new one. If you really are 100% sure you won't use the bike for a few months you can consider taking it off and throwing it out. Or making art out of it.
I use a bucket of warm water, degreaser, a sponge and some old rags for cleaning. Sometimes I also use a toothbrush to get to those hard to reach places. A generic or bike specific cleaning product can help. I use Muc-Off Cleaner a lot (I once bought 5L of it...).
Do make sure the bike is dry when you store it. You do not want parts of it corroding/rusting because you forgot to dry it properly.
Charge that Di2 battery and store it
Specific to Di2 bikes is how you handle the battery. If you're not using the bike for three months or more, this is what you should do:
- Make sure the battery charge level is 50% or higher.
- If it isn't, charge the battery. (just charge to 100%)
- Charge the battery at least once every 6 months.
- Make sure the battery is stored in a 10C - 20C environment.
Shimano says the battery should be removed from the bike when you're not using it for a couple of months. Personally, I have never done this, but temperatures in my shed don't get below 5C-10C all that often.
If you do remove the battery, take care.
Generally the Di2 battery has an EW-SD50 wire running from it to the Junction B, located somewhere around the bottom bracket area. When you take out the battery and disconnect the wire, make sure you do not pull too hard. Doing so could unplug wires at the junction B and you definitely do not want that.
Getting to the junction B usually involves removing the bottom bracket.
Once you return to riding, charge the battery fully before your first ride.
Note that if you have disconnected the battery, make sure the electric wire is really plugged in when you start riding again. The wire should snap into place firmly - having it come loose mid-ride would be really frustrating!
12-speed Di2 - don't forget the shift lever batteries
Are you on 12-speed wireless Di2? Then don't forget to remove your shift lever batteries. Reading the manual for these levers carefully, Shimano recommends taking out the battery if you're not using the bike for a long time.
Shimano do not explicitly state what they consider to be a long time, but I'd say about two-three months qualifies.
Taking the battery out is relatively easy - the process is explained on the second page of the wireless shift lever manual. Simply take out the batteries, store them inside and then reinstall them when you go out riding again.