At present, the energy supply for the electronic equipment of the soldier is problematic. Each component has: its own battery pack. These battery packs are not interchangeable and each requires its own charger. Furthermore, because they are all dimensioned to deliver the peak power for each item of equipment, this leads to a higher battery weight than necessary. It is expected that the system of the future soldier will use a central power source to supply the energy for all the different components. An energy bus will be integrated within the soldier's system for this. The different components will generate their required voltages from the bus voltage by using high efficiency dc/dc converters. The use of an energy bus with local voltage conversion will facilitate interoperability between different forces. The energy sources can easily be exchanged. For the near future, batteries are still considered to be the best option for the energy source. Rechargeable batteries are preferred above non-rechargeable ones due to logistic and environmental problems. For the long-term replacement of batteries, the direct methanol fuel cell (DMFC) is considered a viable option. Several different battery packs were tested for their capability to supply both the required energy and power during a 24 h mission. The tests were carried out with a controlled power method, as maximum power should be deliverable during 10% of the operation time.