use rechargeable aaa battery , with the Battery Saver feature turn on , about two hour . sometimes I get more use alkaline , but not much more . honestly , this unit be worthless , because I can not trust the battery . Order a Garmin Etrex Legend instead . it be not much more expensive , larger or heavier , and it include a base map of road , town , and shoreline . the Legend come with a cable to transfer datum from you computer . the Legend 's screen be a bit larger , but show much more detail . and - the battery last hour and hour .