One of the smartest decisions SRAM made when designing the eTap wireless platform was standardizing a single battery across the entire ecosystem, and this is that battery. The same power unit is interchangeable between front and rear eTap AXS derailleurs, Eagle AXS derailleurs, and the RockShox Reverb AXS seatpost , which means one spare in your saddle bag covers a road bike, a mountain bike, and a dropper post. If you're running any SRAM wireless system — original 11-speed Red eTap, current 12-speed AXS road, XPLR gravel, Eagle mountain, or a Reverb AXS post — this is the replacement or spare you need.

The battery ships with the terminal cover that protects the contacts during transport and storage. Keep the cover on any battery that isn't installed on a derailleur or post — the exposed contacts are the weak point when a loose battery is bouncing around in a jersey pocket or hydration pack with keys and coins. Charge time is 60 minutes or less from a dead battery on the SRAM AXS charger (sold separately), so topping off before a long ride or a race is quick.

Runtime varies by component and shifting frequency, but the practical takeaway is that road AXS derailleurs typically go months between charges under normal riding, while Eagle AXS mountain and Reverb AXS dropper posts turn over faster because they cycle more often. The universal design means you can hot-swap between components in seconds — pull the battery off the front derailleur to keep the rear alive on a ride, or move a spare from the dropper to a derailleur mid-trip. That interchangeability is the whole argument for carrying a spare: one $65 battery is insurance for every AXS component you own.... Read More