Mobile power supply device comprising: a housing for accommodating a battery block and an adapter circuit, the adapter circuit being designed as a DC-AC converter and receiving a DC voltage, converting said DC voltage into an AC voltage and outputting a sinusoidal AC voltage, a first connection terminal which is connected to the adapter circuit and is designed to output the sinusoidal AC voltage, a second connection terminal which is connected to the battery block and is designed to receive a voltage, a switching device for switching the mobile power supply device on or off, a charger for adapting the voltage supplied via the second connection terminal and for controlling a charging process of the battery block, and a battery management system which is coupled to the battery block and monitors and controls the charging and/or discharging process of the battery block, characterized in that the battery block is composed of a plurality of battery packs (30a-30g) which are connected in series, each battery pack (30a-30g) comprising at least two battery cells which are designed as cylindrical cells and are connected in parallel with one another, each battery cell having a positive and a negative electrical connection contact which are arranged on opposite ends of the battery cell, the electrically positive connection contacts of the battery cells being connected to a first connection structure and the electrically negative connection contacts of the battery cells being connected to a second connection structure, the first and the second connection structure being arranged on opposite ends of the battery pack, and each connection structure having a current resistance which corresponds to the sum of the individual currents of each connected battery cell, each battery cell being connected to the first connection structure by means of one connection element in each case and being connected to the second connection structure by means of a further connection element in each case, a cross section of the particular connection element being adapted to a predetermined maximum current of a battery cell, the battery cells of a battery pack (30a-30g) being inserted into holding structures which are made of electrically insulating material and are used to fix the individual battery cells, the connection structures each being placed on the holding structures and having contact holes which allow access to the electrical connection contacts of the battery cells. a housing for accommodating a battery block and an adapter circuit, the adapter circuit being designed as a DC-AC converter and receiving a DC voltage, converting said DC voltage into an AC voltage and outputting a sinusoidal AC voltage, a first connection terminal which is connected to the adapter circuit and is designed to output the sinusoidal AC voltage, a second connection terminal which is connected to the battery block and is designed to receive a voltage, a switching device for switching the mobile power supply device on or off, a charger for adapting the voltage supplied via the second connection terminal and for controlling a charging process of the battery block, and a battery management system which is coupled to the battery block and monitors and controls the charging and/or discharging process of the battery block, characterized in that the battery block is composed of a plurality of battery packs (30a-30g) which are connected in series, each battery pack (30a-30g) comprising at least two battery cells which are designed as cylindrical cells and are connected in parallel with one another, each battery cell having a positive and a negative electrical connection contact which are arranged on opposite ends of the battery cell, the electrically positive connection contacts of the battery cells being connected to a first connection structure and the electrically negative connection contacts of the battery cells being connected to a second connection structure, the first and the second connection structure being arranged on opposite ends of the battery pack, and each connection structure having a current resistance which corresponds to the sum of the individual currents of each connected battery cell, each battery cell being connected to the first connection structure by means of one connection element in each case and being connected to the second connection structure by means of a further connection element in each case, a cross section of the particular connection element being adapted to a predetermined maximum current of a battery cell, the battery cells of a battery pack (30a-30g) being inserted into holding structures which are made of electrically insulating material and are used to fix the individual battery cells, the connection structures each being placed on the holding structures and having contact holes which allow access to the electrical connection contacts of the battery cells.