Yes, the battery is simple and quick to change. Full instructions attached, and below.

  1. Using a standard 2mm allen (hex) key (usually the smallest one on a typical Bicycle multitool) undo the screw in the center of the battery cover in a counterclockwise motion.
  2. Remove the cover.
  3. Replace the batteries with two SR44 or 357 type button cells. They must be silver oxide, not alkaline.  Make sure the positive face (+) is uppermost.
  4. Replace the battery cover. It is important to match the clear plastic light pipe on the inside face of the battery cover into the small hole that is in the battery socket.* Take care tightening the screw, sealing is NOT dependent of screw torque. Slowly tighten the screw until it comes to a mechanical stop – do not tighten any further.
  5. The LED inside flashes when the cover is replaced and is visible through the light tube. Some models only flash once and others flash or show steady for some time. If the green LED is flashing, use your magnet to wave near the RF cover till the lights turn off. Once the green LED is off, your cranks are ready for operation. 
    Please note that if you do not stop the lights flashing, your batteries will drain quickly!

*Installing the covers incorrectly and then forcing the cover closed can lead to crush or deform the light pipe which can crack the joint and let water in.