We have developed the compact and low power-consuming printer unit PTMTL27. This unit is designed especially for built-in use in mobile devices such as digital still cameras and camcorders. The unit is roughly the size of a business card, is 17.7mm thick and weighs 135g. Printing is done by the thermal transfer variable dot scale method.As a matter of course, battery-driven operation is indispensable for mobile applications. Therefore the structure around the heat elements of the print head and the drive method were optimized in order to reduce power consumption, and print operation by battery was attained. And the number of printable pages using various kinds of dry batteries is simulated in this paper.