SRAM's eTAP and AXS systems are really powerful. Their batteries are easy, quick to recharge, removable and attached to the front derailleur and rear derailleur. Installation is a piece of cake without cables. The SRAM eTap / AXS battery is the power source for the eTap system. The same power unit is interchangeable between front and rear derailleurs. Up to 1000 kilometers of riding per 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.