SRAM eTap batteries are literally a snap to remove and charge.
Just flip the tool-free battery latch up and slide the battery up and out of the derailleur. Then snap the battery into the USB powered charger and connect the charger to any USB power source or A/C USB adaptor.
A full charge takes just 45 minutes to complete.
Compatibility: All SRAM Etap Derrailleur Batteries
(Comes without battery)