The objective of this work was to integrate a lithium ion battery pack, together with its management system, into a hydrogen fuel cell drive train contained in a lightweight city car. Electronic units were designed to link the drive train components using conventional circuitry. These were built, tested and shown to perform according to the design. These circuits allowed start-up of battery management system, motor controller, fuel cell warm-up and torque monitoring. After assembling the fuel cell and battery in the vehicle, full system tests were performed. Analysis of results from vehicle demonstrations showed operation was satisfactory. The conclusion was that the electronic integration was successful, but the design needed optimisation and fine tuning. Eight vehicles were then fitted with the electronically integrated fuel cell-battery power pack. Trials were then started to test the integration more fully, with a duration of 12 months from 2011 to 2012 in the CABLED project. (C) 2012 Elsevier B.V. All rights reserved.