The CatEye EL610 provides sufficient lighting while you are cycling. An internal battery powers the lamp. On one charge, you can expect to get about nine hours of lighting in "Low" mode, or about three hours of lighting in "High" mode. Once the battery drains, it needs to be recharged. However, the battery does not have infinite discharge/recharge capability. Eventually, the battery will no longer hold a sufficient charge and will require replacing.
Push the release button on the side and slide the CatEye light forward to remove it from your bicycle mount. Turn the CatEye over to expose the bottom.
Use the Allen wrench to remove the two screws on the lower edge of the light assembly. Grasp the assembly and pull it off the unit.
Unplug the small cable that attaches the battery to the circuit, and then lift the battery out of the compartment.
Insert the new battery into place. Connect its cable to the connection on the circuit.
Hold the light assembly in place and insert and tighten the two Allen screws to finish. Plug the CatEye into its charger and allow it to charge for four hours before using the new battery.
Order your replacement battery from CatEye to ensure compatibility.