The usage time is an important part of the specification for products powered bybatteries. The usage time is affected by a number of different elements; technical,environmental and how the product is being used. The method to determine theusage time is intended to define how measurements and calculations are to berealized along with influencing factors to keep in mind. With support from thismethod the intention is to gain control on how well the established usage time canbe expected to cohere with the real value and what affects the value.The study is done specifically for hearing protectors with battery powered built inelectronically functions. The functions can be level dependent function forambient hearing, 2-way radio communication, Bluetooth or FM-radio.The first chapter of the report describes the literature study performed in theproject. This study handles factors affecting measurements, factors with need tobe considered in the measurement situation and how deviations are handled.The following chapter begins with a description on previously used measurementtechniques for determination of the usage time. This is followed by a descriptionof three different methods developed in this project. A description of a couple ofmeasurements performed to investigate factors that affects the usage time is alsoincluded in this chapter.In the chapter describing the analysis of the study, the three methods developed inthis project are analyzed. This analyze is performed with the formulation ofquestion for the project, what has appeared in the literature study and themeasurements performed.The summary from the project includes factors affecting the measurement andhow to handle deviations in order to keep them as low as possible. The differentfunctions in the products affects the usage time in different proportions. Themost prominent factors are the balance of how much different functions are beingused when the usage time are decided, how batteries behave in different situationsand how the measurement equipment and the connection of the same affects themeasurement result.As part of the summary the advantages with one of the three methods developedare described and compared to the other two developed test methods. Thepreferred method uses usage time logging in real time during a test situation wherethe product is controlled to work in a situation trying to emulate normal use.