Below is an idea of how long your batteries can last on the modes available.Note these are tested under the condition the tracker has good reception and outdoor at all times. If the tracker spends a lot of time under shelter or indoor it will hunt harder for signal and thus decrease battery life under the rated hours below. Urgent mode = 30 seconds, battery life = 7-9 hours (Petrek GPS) 3-6 hours (Petrek 3G) depending on GPS/GSM reception and your pet’s activeness. Best used only in an emergency when you need to zero in on your pet. Normal mode = 5-10 min, battery life = 14-20 Hours(Petrek GPS) 7-10 Hours (Petrek 3G) depending on GPS and GSM reception and your pet’s activeness. Best used for naughty dogs that do wander off frequently or when you want to have a good idea of where your cat roams during the day. Power saving mode = 2 hours, battery life = 3-8 days (Petrek GPS) 2-4 Days (Petrek 3G) depending on GPS and GSM reception and your pet’s activeness. Best used for pets you have tracked for few weeks and have learned their patterns and where they normally wander or visit. You can set a Geo-fencing parameter in the area and still get alerted if they decide to go further than they normally do one day, this will switch to normal mode if it is triggered to help you get them back quicker, you can also change to urgent mode immediately. Note: Battery life can change significantly depending on usage and reception. In bad reception areas the Petrek GPS will constantly search for better signal and thus use more power and reduce battery life. If in a area with good reception while with less active pet the battery life will be extend further.  If your pet stays indoors frequently the battery will decrease faster.