Originally Posted by
Bandera
Yes, one is mechanically operated and the other relies on a battery powered motor to shift. When the other's battery is not charged it does not function. It is not broken, "it is dead". There is no such thing as a "dead" cable, leave a mechanical bike hanging unattended for weeks or months or years and it will function properly. Batteries are inherently less reliable.
-Bandera
Weird... I have a lot of batteries in my life. Not one has completely died without warning. I have had a mechanical.brifter break. I trust electronics, and my ability to be responsible enough to charge a battery, more than I trust tiny mechanical parts.
And cables do break, resulting in a dead brifter. Yes, bike shops have cables. They also have Di2 batteries, at least where I am. Unless charging a battery when you charge your Garmin is really hard for you, you shouldn't have an issue.