Abstract: A battery unit may be used in devices and appliances in which a particularly light and flat battery is desired, such as in particular portable telephones. The battery unit has a housing in which one or several cells generating electricity are provided, such as, for example, a lithium polymer cell. The battery unit is provided with output contacts by means of which the cells can be electrically connected to an appliance, for example by means of resilient contacts present in the appliance. The battery unit is further provided with a housing having a number of external walls such as an upper wall, a bottom wall, and side walls. The housing is internally provided with a substantially flat frame with flat ribs for the purpose of reinforcement and one or several recesses between them. The cell or cells is (are) provided in a recess, possibly in several respective recesses, of the frame.