Originally Posted by
Racing Dan
I appears the non removable battery is only fixed in place to circumvent the SRAM patented "electronic derailleur with removable battery"

. The battery itself is similar to the SRAM batt. but fixed in place with a couple of screws vs a latch. Im betting you could buy a spare and replace it yourself.
I think SRAM own the "front-rear interchangeable batteries" space, not "removable batteries". Campagnolo don't seem to have run into any legal issues with their removable battery system - however, theirs are not F-R interchangeable.