A shunt regulator is a type of a battery charge regulator in which the charging current is controlled by a switch or transistor connected in parallel with the device that is providing the charge, such as a solar panel. Overcharging of the battery is prevented by shorting the photovoltaic output. Shunt regulators are common in photovoltaic systems as they are relatively cheap to build and simple to design. Series regulator usually have better control and charge characteristics.