This paper describes a rapid test-procedure that can be used to derive parameters of a proposed battery model. The battery model is a non-linear dynamic equivalent circuit model, which is based on Randle's model for electrochemical impedance [J. Power Sources 54 (1995) 393]. The level of sophistication has been selected such that it gives a satisfactory prediction of battery performance, but simple enough to enable on-line identification and adaptation of model parameters based on measurements of terminal voltage, current and temperature during usage. The paper also presents test data for a commercial 100 Ah battery including ageing effects. (C) 2004 Elsevier B.V. All rights reserved.