I love my SRAM eTap wireless electronic derailleurs! I installed my first set on my old Tarmac over two years ago and liked it so much I installed a second set on my Thesis gravel bike. The other day the tab broke off one of my eTap batteries. An informal poll of my riding buddies identified three other eTap users in possession of batteries with broken tabs. These batteries aren’t cheap, and I am, so I began plotting a repair. Searching on the internet led me to lots of lamenting, one guy who fabricated a multi-layer carbon fiber tab (Really?), and one guy who attached an appropriately shaped strip of brass to his battery with double-sided tape.
Commentary on the internet suggested that SRAM would replace broken batteries under warranty, sometimes immediately, sometimes with a wait, and sometimes subject to the user’s relationship with their local bike shop. And if you bought it off the internet, walking into your LBS and asking for a warranty replacement seems kinda cheesy. Besides, I don’t want a new battery that might suffer the same fate. I want something better, and I don’t know if SRAM identified a specific problem with a batch of batteries or something.
I liked the guy’s brass strip idea but I felt his design could use some improvement, so I did.
Here is my broken battery after filing away a channel to accommodate the ~0.5mm thick brass strip. The battery case is plenty thick enough to accommodate the material removal.
Here is my brass strip ready to be super-glued in place after a test-fit on both derailleurs to ensure correct location of the tab.
And finally, super-glued, with a few strips of Gorilla tape just in case, because as my friend Dougie says about backups – “Two is one and one is none.”
I thought everything was good to go. I tested my repair in both derailleurs. It fit great. Then I tried to put it in the charger and it wouldn’t snap in! It turns out my tab was a bit too long. I filed it down and now everything is good.
In case you care, my repair resulted in a 2.4 gram weight increase. That makes me wonder if a charged battery weighs more than a discharged battery. What do you think?