Method for powering up a medical device powered by a battery, wherein the method includes executing an initial battery test, the initial battery test including the steps of: a) determining a no-test-load voltage U NoTestLoad of the battery without a test load R Test being connected to the battery; b) providing an alarm if the no-test-load voltage U NoTestLoad is below a predetermined no-test-load voltage threshold U Threshold,NoTestLoad and terminating the method; c) if the no-test-load voltage U NoTestLoad is above the no-test-load voltage threshold U Threshold,NoTestLoad executing the steps of: c1) determining a test-load voltage U TestLoad of the battery with a test load R Test being connected to the battery; c2) comparing a difference voltage ΔU between the no-test-load voltage U NoTestLoad and the test-load voltage U TestLoad with a difference voltage threshold Δ U Treshold, the difference voltage threshold Δ U Treshold being predefined in dependence of the no-test-load voltage U NoTestLoad; c3) if the difference voltage ΔU is above the difference voltage threshold Δ U Treshold, providing an alarm; wherein the method further includes executing subsequent steps of the method if the difference voltage Δ U is below the difference voltage threshold Δ U Treshold. characterized in that said difference voltage threshold Δ U Treshold predefined in dependence of the no-test-load voltage U NoTestLoad has been determined by a method including the steps of: experimentally determining a functional relation between values of an effective internal resistance R i and values of an open-circuit voltage U 0 for which the battery is capable of powering-up the medical device; determining a minimum no-test-load voltage U NoTestLoad,min of the battery for powering up the medical device without a test load R Test being connected to the battery as a function of the open-circuit voltage U 0 based on the functional relation as determined in step; determining a minimum test-load voltage U TestLoad,min of the battery for powering up the medical device with a test load R Test being connected to the battery as a function of the open-circuit voltage U 0 based on the functional relation as determined in step; computing the difference voltage threshold Δ U Treshold from the difference between the minimum no-test-load voltage U NoTestLoad,min and the minimum test-load voltage U TestLoad,min in dependence of the minimum no-test-load voltage U NoTestLoad,min with the open circuit voltage U 0 as parameter. a) determining a no-test-load voltage U NoTestLoad of the battery without a test load R Test being connected to the battery; b) providing an alarm if the no-test-load voltage U NoTestLoad is below a predetermined no-test-load voltage threshold U Threshold,NoTestLoad and terminating the method; c) if the no-test-load voltage U NoTestLoad is above the no-test-load voltage threshold U Threshold,NoTestLoad executing the steps of: c1) determining a test-load voltage U TestLoad of the battery with a test load R Test being connected to the battery; c2) comparing a difference voltage ΔU between the no-test-load voltage U NoTestLoad and the test-load voltage U TestLoad with a difference voltage threshold Δ U Treshold, the difference voltage threshold Δ U Treshold being predefined in dependence of the no-test-load voltage U NoTestLoad; c3) if the difference voltage ΔU is above the difference voltage threshold Δ U Treshold, providing an alarm; c1) determining a test-load voltage U TestLoad of the battery with a test load R Test being connected to the battery; c2) comparing a difference voltage ΔU between the no-test-load voltage U NoTestLoad and the test-load voltage U TestLoad with a difference voltage threshold Δ U Treshold, the difference voltage threshold Δ U Treshold being predefined in dependence of the no-test-load voltage U NoTestLoad; c3) if the difference voltage ΔU is above the difference voltage threshold Δ U Treshold, providing an alarm; experimentally determining a functional relation between values of an effective internal resistance R i and values of an open-circuit voltage U 0 for which the battery is capable of powering-up the medical device; determining a minimum no-test-load voltage U NoTestLoad,min of the battery for powering up the medical device without a test load R Test being connected to the battery as a function of the open-circuit voltage U 0 based on the functional relation as determined in step; determining a minimum test-load voltage U TestLoad,min of the battery for powering up the medical device with a test load R Test being connected to the battery as a function of the open-circuit voltage U 0 based on the functional relation as determined in step; computing the difference voltage threshold Δ U Treshold from the difference between the minimum no-test-load voltage U NoTestLoad,min and the minimum test-load voltage U TestLoad,min in dependence of the minimum no-test-load voltage U NoTestLoad,min with the open circuit voltage U 0 as parameter.