A capacitive energy-storage for a mobile working machine

A capacitor module comprises a capacitor element (101), a first voltage terminal (102) connected to a first pole of the capacitor element, and a second voltage terminal (103) connected to a second pole of the capacitor element. The capacitor module further comprises a cooling duct system (104) for cooling the capacitor element, and a housing (105) encapsulating the capacitor element and the cooling duct system. The housing comprises wiring lead-throughs (106) for the first and second voltage terminals and piping lead-throughs (107) for the cooling duct system. As the capacitive module is encapsulated and comprises the cooling ducts and the wiring and piping lead-throughs, modular capacitive energy-storages of different sizes can be built by interconnecting capacitor modules of the kind described above, and there is no need to build separately an encapsulation provided with cooling ducts.