FieldClock uses your device's GPS and camera hardware extensively and the impact on battery life is directly related to how much you use the app.
In our testing, we have found that using the app for simple tasks such as clocking employees in/out drains the battery minimally. However, if you are using the app to record piecework in high-volume situations (such as picking large quantities of cherries), the battery will suffer greater loss at an increased rate.
If you are picking high volumes of pieces in the field, we recommend having portable chargers available to your crew.