In this paper, the Keller-Box method has been applied to the coupled one-dimensional electrochemical transport equations in order to simulate lead-acid batteries numerically. The advantages and disadvantages of this method have been discussed. The results indicate that the Keller-Box method is a suitable method for integration of electrochemical transport equations both in integrated and multi-region formulation. The boundary conditions and interface conditions (in the case of multi-region approach) can be implemented easily and require no special routine (for off-diagonal terms). In addition, the effect of acid concentration dependency of open circuit voltage has also been investigated. (c) 2005 Elsevier B.V. All rights reserved.