To charge AXS derailleur batteries, remove the battery from the derailleur and charge them on the AXS battery charger. These derailleur batteries are easy to remove without any tools.
The charger uses a micro-USB interface, and a standard USB to micro-USB cable is used to connect the charger to the power source. The power source can be a USB power source, such as a computer, but A/C home power adapters will also work!
For information on battery removal, installation, charging, and battery indicator LEDs, see the SRAM RED eTap System Overview video.