According to an example aspect of the present invention, there is provided a direct current (DC) to DC converter module for use between an electrical storage device, electric power source and an electric load. The converter module having at least one DC to DC converter; first input terminals connected to inputs of the DC to DC converter; output terminals connected to outputs of the DC to DC converter; second input terminals connected to the outputs of the DC to DC converter; and control circuitry connected to the DC to DC converter, the control circuitry being configured to monitor at least one of a voltage and current at the second input terminals. The control circuitry is configured to control the DC to DC converter in order to adjust a gain or conversion factor of the DC to DC converter based at least partially on the monitored voltage and/or current at the second input terminals.