Your Wave mini is equipped with 3x AA alkaline batteries. This gives your Wave Mini up to 3 years of battery life! When it comes time to replace the batteries in your Mini use a good quality brand (such as Duracell or Energizer) in order to get another 3 years of battery life. Rechargeable batteries not recommended for any of our devices as they run a lower voltage and have not been thoroughly tested. 

To replace your batteries all you need to do is remove the magnetic back plate on your Mini and swap out the old batteries with new ones. 

The lifespan of the Wave Mini is similar to that of a regular smoke detector. Just change the batteries to continue to measure :)