Originally Posted by datlas

Got a Di2 battery question. I figured I should start here before I try the 41.

Reminder my friend installed USED 11s Ultegra Di2 in the Roubaix.

I last charged it about 2 weeks (300 miles) ago.

At the start of today’s ride the battery light indicator on the junction box lit up >50%. Fine.

At the end of today’s ride, which was only 50 miles, just as I crested the last hill, the FD stopped working so clearly the battery is very low. I came home and put it on the charger.

I am wondering how the battery can go from >50% to low in just one short ride. I am wondering if this is typical for an old battery.

Anyone with experience care to comment?