A 5-W direct methanol fuel cell (DMFC) stack has been developed to investigate the dynamic behaviour of the performance. The stack generates the 5-W peak power with 10 cells of 3 cm x 3 cm active area. Upon changing the load conditions, the transient behaviour of the stack voltage is monitored to evaluate the speed at which the stack adapts to the changes. The transient characteristics of the stack current are also studied with continuously changing fuel flow rates of 2 M methanol solution and air. The optimum operating conditions for the stable operation of the 5-W DMFC stacks are reported. (c) 2005 Elsevier B.V. All rights reserved.