A user-friendly differential voltage analysis software has been developed and is described here. High-precision reference potential-specific capacity data for Li/negative electrode and Li/positive electrodes, as well as the cycled full cell potential-specific capacity, must be supplied by the user. From these, the differential voltage versus capacity, dV/dQ vs. Q, of a full Li-ion cell is calculated and compared to experiment. The calculated dV/dQ vs. Q curve has four adjustable parameters which are optimized manually with slider bars or automatically by least squares fitting of the calculation to experiment. The parameters are the positive electrode mass, the negative electrode mass, the positive electrode slippage and the negative electrode slippage. Examples of the use of the program are given for graphite/LiCoO2 wound cells cycled for hundreds of cycles. The variation of the four parameters with cycle number give insights into the mechanisms of cell failure equivalent to that which could be obtained with a Li reference electrode inserted within the cell. The software is available free of charge by contacting the authors. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.013209jes] All rights reserved.