For understanding and improving the performance of industrial Si solar cells, it helps to quantify the losses in the various device parts very precisely, because this enhances the predictive power of roadmaps deduced from such analysis. We show how the precision of commonly applied methods for measuring the saturation current density, J(0), can be noticeably improved. Firstly, two methods are compared for determining the optical properties of the samples specifically made for lifetime measurements. Secondly, it is evaluated, which excess carrier density level is best to choose for extracting J(0) of the various device regions. Thirdly, the bulk lifetime is extracted by a combination of measurements and modeling of the surface passivation. (C) 2016 Elsevier B.V. All rights reserved.