There is a wide range of power options available for use with the Active 10, allowing you to choose the one which suits your needs best. AA batteries give you the flexibility to carry spares & easily swap them half way round a walk, whereas the Lithium Polymer rechargeable option could end up being more effective when the unit is used on a regular basis. Whichever option you choose, it is always advisable to remember the power saving tips to get the most from your battery (see the User Guide).